tag:theconversation.com,2011:/africa/topics/ear-5762/articlesEar – The Conversation2022-10-21T12:38:54Ztag:theconversation.com,2011:article/1890412022-10-21T12:38:54Z2022-10-21T12:38:54ZNewly available over-the-counter hearing aids offer many benefits, but consumers should be aware of the potential drawbacks<figure><img src="https://images.theconversation.com/files/490440/original/file-20221018-7297-l8bqgl.jpg?ixlib=rb-1.1.0&rect=8%2C8%2C5583%2C3713&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Over-the-counter hearing aids are now available at pharmacies and big-box stores.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/senior-woman-holding-hearing-aid-close-up-royalty-free-image/926841484?phrase=hearing%20aids&adppopup=true">Mara Ohlsson/Image Source via Getty Images</a></span></figcaption></figure><p>U.S. retailers <a href="https://www.usatoday.com/story/news/health/2022/10/17/over-the-counter-hearing-aids-available/10522017002/">began selling over-the-counter hearing aids</a> on Oct. 17, 2022, a long-awaited move that some experts predict could be a game-changer in <a href="https://www.pbs.org/newshour/health/you-can-now-buy-lower-cost-hearing-aids-over-the-counter-heres-how">making these devices accessible and affordable</a>. A prescription is no longer needed, nor is a visit to a doctor or even a fitting appointment with a hearing specialist. </p>
<p>Instead, Americans <a href="https://www.cnn.com/2022/10/17/health/over-the-counter-hearing-aids-available/index.html">can purchase hearing aids</a> by going online or with a single trip to the nearest pharmacy or big-box store. These aids are only for those with mild to moderate hearing loss. For these consumers, over-the-counter hearing aids clearly offer an appealing alternative. </p>
<p><a href="https://med.virginia.edu/otolaryngology/faculty/bradley-w-kesser-m-d/">As an otologist/neurotologist</a> – that’s someone who specializes in the diseases of the ear – I like to say that while vision binds us to the world, hearing binds us to each other. In my practice, I see firsthand how patients with hearing loss often withdraw socially and become isolated. They don’t want to put themselves in situations where they may mishear or seem disengaged, disinterested or unintelligent. This may be why studies show hearing loss is <a href="https://doi.org/10.1097/MOO.0000000000000825">associated with depression</a> and <a href="https://doi.org/10.1093/geronb/gbab194">cognitive impairment</a>. </p>
<p>So it seems the over-the-counter hearing aids would be a great solution for patients with hearing loss, right? Less hassle and less cost – in many cases, thousands of dollars less – and more people than ever getting the help they need. But it’s not that simple. Occurring just two months after the U.S. Food and Drug Administration’s <a href="https://www.fda.gov/news-events/press-announcements/fda-finalizes-historic-rule-enabling-access-over-counter-hearing-aids-millions-americans">final ruling on the matter</a>, over-the-counter sales of hearing aids come with caveats and even some risks.</p>
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<figcaption><span class="caption">Prior to the availability of over-the-counter devices, only 30% of those over age 70 with hearing loss used hearing aids.</span></figcaption>
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<h2>How hearing loss happens</h2>
<p>Hearing specialists divide hearing loss into two main categories: <a href="https://www.asha.org/public/hearing/conductive-hearing-loss/#:">conductive</a> and <a href="https://www.asha.org/public/hearing/sensorineural-hearing-loss/">sensorineural hearing loss</a>. Conductive loss is caused by any number of things, including ear wax obstruction, a perforation in the ear drum or fluid in the middle ear. Children are more likely than adults to have conductive hearing loss, and most of the time, many of these problems are relatively easy to correct. </p>
<p>But sensorineural hearing loss is caused by a problem occurring in the inner ear, auditory nerve and brain. Most commonly, there is a loss of the tiny cochlear hair cells that <a href="http://www.cochlea.eu/en/hair-cells">convert sounds into an electrical signal</a>. The brain interprets that signal as a bird singing or a child laughing. Hair cell injury is generally permanent and irreversible; those cells do not regenerate in humans, or for that matter, in any mammal. </p>
<p>Whether conductive or sensorineural, hearing aids have proved to be a tremendous boon for patients with hearing loss. One national survey found that in 2019, 7.1% of adults aged 45 and over <a href="https://www.cdc.gov/nchs/products/databriefs/db414.htm">used a hearing aid</a>. </p>
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<figcaption><span class="caption">Over-the-counter hearing aids are not for everyone who has hearing loss.</span></figcaption>
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<h2>Problems with over-the-counter hearing aids</h2>
<p>Before over-the-counter hearing aids became available, patients <a href="https://www.nidcd.nih.gov/health/do-you-need-hearing-test">needed a formal hearing test and assessment</a>. This is critical because not all hearing loss is the same; hearing specialists – both otolaryngologists and audiologists – are trained to decipher the type of hearing loss that a patient is experiencing. From that, they make recommendations on hearing treatment. If a patient needs a hearing aid, a health care professional will <a href="https://www.healthyhearing.com/help/hearing-aids/fitting">fit them with one</a>.</p>
<p>But purchasing an over-the-counter hearing aid requires none of those things – not an ear exam, not a hearing test and not a fitting session. There are many reasons why this shortcut approach, while certainly less expensive and offering easier access, may not be ideal for someone experiencing hearing loss.</p>
<p>First, patients may have a chronic infection or condition that requires medical or surgical management, rather than a hearing aid. Second, some patients may be a candidate for surgical correction of their hearing loss. Third, patients with hearing loss in one ear or a large difference in hearing between the two ears may have a benign growth on the hearing and balance nerve. This often requires surgery or radiation treatment. Again, a hearing aid would not help with this condition. </p>
<p>Additionally, for those who would benefit from an over-the-counter product, not every hearing aid fits every ear – one size most certainly does not fit all. And one more caveat: Over-the-counter hearing aids are not recommended for people under 18. </p>
<p>Finally, some patients may have too much hearing loss for these devices to provide any benefit. Instead, many patients with more advanced hearing loss have <a href="https://www.nidcd.nih.gov/health/cochlear-implants">the option of a cochlear implant</a>, which is essentially a wire with an electrode array surgically placed into the cochlea, the bony “house” of the hair cells situated deep in the skull. The electrodes stimulate the auditory nerve directly, bypassing the damaged hair cells. For these patients, cochlear implants offer <a href="https://www.mayoclinic.org/tests-procedures/cochlear-implants/about/pac-20385021">an exceptional opportunity to hear again</a>. As the technology improves, more people will become candidates for this medical miracle.</p>
<p>About 80% of adults aged 55 to 74 who would benefit from a hearing aid <a href="https://doi.org/10.3109/14992027.2013.769066">do not use them</a>. The new over-the-counter hearing aids hold great promise for the right patients. But buyer beware: They are not panaceas. Not all customers will be satisfied with over-the-counter hearing aids – and a visit to the doctor or audiologist is still critical.</p><img src="https://counter.theconversation.com/content/189041/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Bradley Kesser does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>They are easy to get, and far less costly than prescription hearing aids. But over-the-counter devices are not the answer for everyone with hearing issues.Bradley Kesser, Professor of Otology/Neurotology, University of VirginiaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1708572022-02-07T13:19:05Z2022-02-07T13:19:05ZWhat is earwax?<figure><img src="https://images.theconversation.com/files/442366/original/file-20220124-15-yq8wz2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Step away from the cotton swabs!</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/dirty-cotton-swab-royalty-free-image/92889763">Crazytang/iStock via Getty Images Plus</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
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<blockquote>
<p><strong>What is earwax? – Helen E., age 8, Somerville, Massachusetts</strong></p>
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<p>Imagine you’re watching TV. Suddenly, your ear feels a little itchy. You stick your pinky finger in there and dig around a bit. You pull it out and stare at the little brownish blob on the tip of your finger.</p>
<p>That’s earwax. This kind of waxy ear booger has plagued people for centuries. Tools to remove earwax from thousands of years ago have been discovered <a href="https://www.smithsonianmag.com/smart-news/roman-tweezers-and-metal-q-tip-found-england-180973777/">in ancient Roman</a> and at <a href="https://en.natmus.dk/historical-knowledge/denmark/prehistoric-period-until-1050-ad/the-viking-age/the-people/appearance/">Viking archaeological sites</a>. But if you could snap your fingers and suddenly wish away all the earwax in the world, it might not be as great as you imagine.</p>
<p><a href="https://scholar.google.com/citations?hl=en&view_op=list_works&gmla=AJsN-F4yOWs68gzIWGmiRrwuM774uc4c9CeuLu0TJXl_xBJ3twogC0YfkoiOkwNonmNJsHeRrSK32Hx1CO_oWUbaPjpDlG48Zw&user=feLpbjEAAAAJ">I’m a pediatric otolaryngologist</a> – otherwise known as an ear, nose and throat doctor for children. I work at Seattle Children’s Hospital and mainly see kids who have problems with their ears. Sometimes I encounter a patient who has something in their ear that shouldn’t be there – insects, gummy worms and beautiful gemstone beads are some of my personal favorites that I’ve removed. But what I see all the time is a lot of earwax.</p>
<p>Your ear canal is lined with skin cells, as well as different glands that release various substances into the canal. Earwax is produced in your ear canal and is basically a <a href="https://en.wikipedia.org/wiki/Earwax">mix of skin cells, sweat and fatty oils</a>. These things mix together to form small – or sometimes rather big – globs of golden-brown gunk.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/442367/original/file-20220124-19-fbn864.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="cross-section diagram of the human ear system" src="https://images.theconversation.com/files/442367/original/file-20220124-19-fbn864.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/442367/original/file-20220124-19-fbn864.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=448&fit=crop&dpr=1 600w, https://images.theconversation.com/files/442367/original/file-20220124-19-fbn864.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=448&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/442367/original/file-20220124-19-fbn864.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=448&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/442367/original/file-20220124-19-fbn864.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=563&fit=crop&dpr=1 754w, https://images.theconversation.com/files/442367/original/file-20220124-19-fbn864.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=563&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/442367/original/file-20220124-19-fbn864.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=563&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Earwax is found in the outer part of your ear, in the ear canal.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/human-ear-anatomy-royalty-free-illustration/1254417864">Ace2020/iStock via Getty Images Plus</a></span>
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<p>Everyone’s earwax is unique. Some is more pasty, some is dry, some is yellow, brown or black. Scientists have figured out a <a href="https://doi.org/10.1038/ng1733">gene that seems to calibrate</a> how wet or dry your wax is. So, if your wax is really pasty and stinky, it’s another thing you can blame on your parents.</p>
<p>While you might think it is just a nuisance, earwax actually plays some important roles. It helps keep the skin in your ear healthy and moist, and doctors think it may <a href="https://doi.org/10.1056/NEJM197105132841913">protect the ear canal from infections</a>. If there were no earwax in the world, your ears would feel dry and itchy. You would probably scratch at them constantly and get ear canal infections more frequently.</p>
<p>But maybe you’re convinced a buildup of earwax is making your ears itch – not to mention preventing you from hearing when you’re called to dinner. In that case, is it better to get it out of there?</p>
<p>Many people are tempted to stick something in their ears to try to get wax out and give the ear a nice little scratch. The problem is that while you might get a little wax out, you’re probably pushing more in than you’re extracting. If you keep pushing more and more in, sooner or later your ear canal will be packed and overflowing with waxy goodness.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/442348/original/file-20220124-13-rrfafe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="little girl poking her finger in her ear" src="https://images.theconversation.com/files/442348/original/file-20220124-13-rrfafe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/442348/original/file-20220124-13-rrfafe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/442348/original/file-20220124-13-rrfafe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/442348/original/file-20220124-13-rrfafe.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/442348/original/file-20220124-13-rrfafe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/442348/original/file-20220124-13-rrfafe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/442348/original/file-20220124-13-rrfafe.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Don’t be hard on your earwax – it’s actually doing an important job.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/little-girl-plug-ears-with-fingers-on-brown-royalty-free-image/1353608950">kool99/E+ via Getty Images</a></span>
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<p>So what is the best way to remove it? Believe it or not, on its own the ear canal naturally <a href="https://pubmed.ncbi.nlm.nih.gov/6085805/">pushes earwax out of your ear</a>. <a href="https://doi.org/10.1002/aja.1001840408">As skin grows in the ear canal</a>, it forms a natural conveyor belt for the earwax. In general, it should slowly migrate to the outside of your ear canal and just fall out when you run around or bathe. When you chew, your jaw movement also seems to help wax come out of your ear.</p>
<p>This is a natural process and a long journey to freedom for those little ear boogers. They want to get out of your ear canal, too, so don’t push them back in by sticking a Q-tip in your ear. Some people mistakenly think lighting a candle by your ear is a great way create a vacuum and suck wax out of your ear. <a href="https://www.audiologyresearch.org/ear-candling/">It isn’t</a> – research shows that <a href="https://www.mayoclinic.org/healthy-lifestyle/consumer-health/expert-answers/ear-candling/faq-20058212">it doesn’t actually work</a>, so please don’t light any fires next to your head.</p>
<p>Sometimes it can help to use different types of ear drops to soften up wax and help it come out on its own. There are some drops you can buy at the store, and some simple products like mineral oil that can also do the trick. <a href="https://doi.org/10.1177/0194599816680327">If your ear gets too full of wax</a>, you might need to see your doctor to have it carefully cleaned out. Don’t try this at home! </p>
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<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/170857/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Henry Ou has previously received funding from the National Institutes of Health - National Institute on Deafness and Other Communication Disorders, American Society of Pediatric Otolaryngology, National Organization for Hearing Research Foundation, Capita Foundation, and the American Otologic Society,</span></em></p>That brownish/yellowish gunk that comes out on your finger if you scratch deep inside your ear? It actually serves an important purpose in your body.Henry Ou, Associate Professor of Otolaryngology, School of Medicine, University of WashingtonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1711712021-11-24T14:44:52Z2021-11-24T14:44:52ZGreat headphones blend physics, anatomy and psychology – but what you like to listen to is also important for choosing the right pair<figure><img src="https://images.theconversation.com/files/433547/original/file-20211123-18-1o2lao8.jpg?ixlib=rb-1.1.0&rect=82%2C112%2C3448%2C3050&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Headphone designers have to balance scientific limitations with human preferences.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/close-up-of-headphones-on-microphone-stand-in-royalty-free-image/743693059?adppopup=true">Vladimir Godnik via Getty Images</a></span></figcaption></figure><p>Between music, podcasts, gaming and the unlimited supply of online content, most people <a href="https://brandongaille.com/23-headphone-industry-statistics-and-trends/">spend hours a week wearing headphones</a>. Perhaps you are considering a new pair for the holidays, but with so many options on the market, it can be hard to know what to choose.</p>
<p>I am a professional musician and a professor of <a href="https://et.iupui.edu/people/hsut">music technology who studies acoustics</a>. My work investigates the intersection between <a href="https://www.aes.org/e-lib/online/browse.cfm?elib=14210">the scientific</a>, artistic and <a href="https://www.aes.org/e-lib/browse.cfm?elib=19774">subjective human elements</a> of sound. Choosing the right headphones involves considering all three of those aspects, so what makes for a truly good pair?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/433529/original/file-20211123-20-iz3eja.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing a wave and areas of higher density and lower density dots." src="https://images.theconversation.com/files/433529/original/file-20211123-20-iz3eja.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/433529/original/file-20211123-20-iz3eja.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=261&fit=crop&dpr=1 600w, https://images.theconversation.com/files/433529/original/file-20211123-20-iz3eja.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=261&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/433529/original/file-20211123-20-iz3eja.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=261&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/433529/original/file-20211123-20-iz3eja.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=328&fit=crop&dpr=1 754w, https://images.theconversation.com/files/433529/original/file-20211123-20-iz3eja.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=328&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/433529/original/file-20211123-20-iz3eja.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=328&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Sound is simply a series of low pressure and high pressure areas where air molecules, represented by the small dots, compress or spread apart.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:CPT-sound-physical-manifestation.svg#/media/File:CPT-sound-physical-manifestation.svg">Pluke/WikimediaCommons</a></span>
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<h2>What is sound really?</h2>
<p>In physics, sound is made of air vibrations consisting of a series of high and low pressure zones. These are the cycles of a sound wave.</p>
<p>Counting the number of cycles that occur per second <a href="https://www.pearson.com/us/higher-education/program/Rossing-Science-of-Sound-The-3rd-Edition/PGM175267.html">determines the frequency, or pitch, of the sound</a>. Higher frequencies mean higher pitches. Scientists describe frequencies in hertz, so a 500 Hz sound goes through 500 complete cycles of low pressure and high pressure per second. </p>
<p>The loudness, or amplitude, of a sound is determined by the maximum pressure of a wave. The higher the pressure, the louder the sound. </p>
<p>To create sound, headphones turn an electrical audio signal into these cycles of high and low pressure that our ears interpret as sound.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/433533/original/file-20211123-13-12mj28o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram of a human ear." src="https://images.theconversation.com/files/433533/original/file-20211123-13-12mj28o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/433533/original/file-20211123-13-12mj28o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=455&fit=crop&dpr=1 600w, https://images.theconversation.com/files/433533/original/file-20211123-13-12mj28o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=455&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/433533/original/file-20211123-13-12mj28o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=455&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/433533/original/file-20211123-13-12mj28o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=572&fit=crop&dpr=1 754w, https://images.theconversation.com/files/433533/original/file-20211123-13-12mj28o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=572&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/433533/original/file-20211123-13-12mj28o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=572&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The human ear is a complex system that turns vibrations in the air into electrical signals that go to the brain.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Ear-anatomy-text-small-en.svg#/media/File:Ear-anatomy-text-small-en.svg">Iain/WikimediaCommons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>The human ear</h2>
<p>Human ears are incredible sensors. The average person can hear a huge range of pitches and different levels of loudness. So how does the ear work?</p>
<p>When sound enters your ear, your eardrum translates the air vibrations into mechanical vibrations of the tiny middle ear bones. These mechanical vibrations become fluid vibrations in your inner ear. Sensitive nerves then turn those vibrations into electrical signals that your brain interprets as sound. </p>
<p>Although people can hear a range of pitches roughly from 20 Hz to 20,000 Hz, human hearing <a href="https://doi.org/10.1002/j.1538-7305.1933.tb00403.x">does not respond equally well at all frequencies</a>. </p>
<p>For example, if a low frequency rumble and a higher pitched bird have the same loudness, you would actually perceive the rumble to be quieter than the bird. Generally speaking, the human ear is <a href="https://doi.org/10.1121/1.1915637">more sensitive to middle frequencies than low or high pitches</a>. Researchers think this may be <a href="https://theconversation.com/testing-ancient-human-hearing-via-fossilized-ear-bones-47973">due to evolutionary factors</a>.</p>
<p>Most people don’t know that hearing sensitivity varies and, frankly, would never need to consider this phenomenon – it is simply how people hear. But headphone engineers definitely need to consider how human perception differs from pure physics. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/433537/original/file-20211123-17-nmyltx.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A cutaway diagram of a speaker." src="https://images.theconversation.com/files/433537/original/file-20211123-17-nmyltx.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/433537/original/file-20211123-17-nmyltx.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=820&fit=crop&dpr=1 600w, https://images.theconversation.com/files/433537/original/file-20211123-17-nmyltx.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=820&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/433537/original/file-20211123-17-nmyltx.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=820&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/433537/original/file-20211123-17-nmyltx.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1030&fit=crop&dpr=1 754w, https://images.theconversation.com/files/433537/original/file-20211123-17-nmyltx.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1030&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/433537/original/file-20211123-17-nmyltx.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1030&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Speakers are fundamentally made of four components, a magnet (1), a coiled wire (2), a spring or suspension (3) and a diaphragm (4).</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Loudspeaker-bass.png#/media/File:Loudspeaker-bass.png">Svjo/WkimediaCommons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>How do headphones work?</h2>
<p>Headphones – both bigger varieties that sit over your ears as well as small earbuds – are just small speakers. Simply put, speakers do the opposite of your ear: They convert the electrical signals from your phone, record player or computer into vibrations in air. </p>
<p>Most speakers are made of four components: a stationary magnet, a wire coil that moves back and forth around that magnet, a diaphragm that pushes air and a suspension that holds the diaphragm.</p>
<p>Electromagnetism states that when a wire is wrapped around a magnet and the current within the wire changes, the <a href="https://www.sciencedirect.com/book/9780240809694/handbook-for-sound-engineers">magnetic field around the wire changes proportionally</a>. When the electrical signal of a song or podcast pulses through the wires in a set of headphones, it changes the current and moves the magnet. The magnet then moves the diaphragm in and out – kind of like a plunger – pushing and compressing air, creating pulses of high pressure and low pressure. This is the music that you hear.</p>
<p>Ideally, a speaker would convert the electrical signals of the input perfectly into sound representations. However, the real physical world has limitations. Things like the size and material of the magnet and diaphragm all prevent a speaker from perfectly matching its output to its input. This leads to distortion and some frequencies being louder or softer than the original. </p>
<p>While no headphone can perfectly recreate the signal, there are infinite different ways to choose to distort that signal. The reason two equally expensive headphones can sound or feel different is that they distort things in different ways. When engineers build new headphones, they have to not only consider how human hearing distorts sound, but also the physical limitations of any speaker.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/433542/original/file-20211123-21-1kgd80t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A man outside wearing headphones." src="https://images.theconversation.com/files/433542/original/file-20211123-21-1kgd80t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/433542/original/file-20211123-21-1kgd80t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/433542/original/file-20211123-21-1kgd80t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/433542/original/file-20211123-21-1kgd80t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/433542/original/file-20211123-21-1kgd80t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/433542/original/file-20211123-21-1kgd80t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/433542/original/file-20211123-21-1kgd80t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">What you like to listen to and how you like your headphones to sound play a huge role in determining what makes for a ‘good’ pair of headphones.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/rear-view-of-man-listening-to-headphones-at-beach-royalty-free-image/543201647?adppopup=true">Matt Dutile/Image Source via Getty Images</a></span>
</figcaption>
</figure>
<h2>Listener preference</h2>
<p>If all the complications of ears and speakers weren’t enough, listeners themselves play a huge role in deciding what makes for a “good” pair of headphones. Aspects like age, experience, culture and music genre preference <a href="http://www.aes.org/e-lib/browse.cfm?elib=17500">all affect what kind of frequency distortion someone will prefer</a>. Headphones are as much <a href="https://www.aes.org/e-lib/online/browse.cfm?elib=16768">a question of personal taste</a> as anything else. </p>
<p>For example, some people prefer bass-heavy headphones for hip-hop music, while classical music listeners may want less frequency distortion. But music or recreational listening aren’t the only things to consider. Headphones for the hearing impaired may highlight frequencies from approximately 1,000 Hz to 5,000 Hz, as <a href="https://doi.org/10.1044/1059-0889.0603.48">this helps to make speech more understandable</a>.</p>
<p>You could certainly play a hip-hop song through headphones designed for the hearing impaired, but most people would agree that the results aren’t going to sound very good. Making sure the headphones you choose match how you are going to use them goes a long way in determining what will sound good.</p>
<p>Ultimately, the science of headphone design, the artistry of the content creators and the human experience all intersect to form the perception of “good” headphones. Despite all these moving pieces, there is one foolproof way to know when headphones are good: choose a good song and put a pair on! Because when all the attributes align, a good pair of headphones can give you the opportunity to be transformed by sound.</p><img src="https://counter.theconversation.com/content/171171/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Timothy Hsu is a member of the Acoustical Society of America and an executive board member for the Indiana Section of the Audio Engineering Society.</span></em></p>There is a lot to consider when buying a new pair of headphones. A professional musician and acoustics researcher explains how the science of sound and quirks of human hearing make for a great listening experience.Timothy Hsu, Assistant Professor of Music and Arts Technology, IUPUILicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1687422021-10-08T04:02:24Z2021-10-08T04:02:24ZDon’t wear earphones all day – your ears need to breathe<figure><img src="https://images.theconversation.com/files/425366/original/file-20211008-19107-vb1res.jpg?ixlib=rb-1.1.0&rect=56%2C0%2C6174%2C4156&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://image.shutterstock.com/image-photo/new-apple-airpods-pro-outdoor-260nw-1588935502.jpg">Shutterstock</a></span></figcaption></figure><p>Wireless earphone sales are booming, with Apple alone selling an estimated <a href="https://www.businessofapps.com/data/apple-statistics/">100 million sets of AirPods</a> in 2020. Being untethered from our phones or devices means we are likely to wear earphones for longer periods.</p>
<p>As a result, you might notice your ears feeling more sticky or waxy. Is this common? And what happens to our ears when we wear earphones?</p>
<p>Although wireless earphones are fairly new to the market, there is a large amount of research investigating the long-term use of <a href="https://pubmed.ncbi.nlm.nih.gov/28846265/">hearing aids</a>, which in many cases, have a similar mechanism. From this research, it appears prolonged use of in-ear devices can cause problems with <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4356173/">earwax</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/are-your-kids-using-headphones-more-during-the-pandemic-heres-how-to-protect-their-ears-139392">Are your kids using headphones more during the pandemic? Here's how to protect their ears</a>
</strong>
</em>
</p>
<hr>
<h2>What does earwax do?</h2>
<p>The production of earwax (also known as <a href="https://www.ncbi.nlm.nih.gov/books/NBK448155/">cerumen</a>) is a normal process in humans and many other mammals. There should always be a thin coating of wax near the opening of the ear canal.</p>
<p>This wax is a waterproof and protective secretion. This acts to moisten the skin of the external ear canal and works as a protective mechanism to prevent infection, providing a barrier for <a href="https://www.ncbi.nlm.nih.gov/books/NBK448155/">insects, bacteria, and water</a>. Wet earwax is brown and sticky, whereas the dry type is more of a white colour.</p>
<p>In fact, earwax is such a great barrier, in the 1800s there were reports of it being used as an effective balm for <a href="https://theconversation.com/what-causes-dry-lips-and-how-can-you-treat-them-does-lip-balm-actually-help-161264">chapped lips</a>!</p>
<p>Earwax is a naturally occurring substance produced in the external portion of the <a href="https://www.ncbi.nlm.nih.gov/books/NBK459335/">ear canal</a>. It is created by the secretions of <a href="https://pubmed.ncbi.nlm.nih.gov/9433685/">oil glands and sweat glands</a> released by the <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4356173/">hair follicles</a>, which then traps dust, bacteria, fungi, hairs and dead skin cells to form the wax. </p>
<p>The external ear canal can be thought of as an escalator system, with the wax always moving towards the outside, preventing the ears from becoming filled with dead skin cells.</p>
<p>This migration of earwax is also aided by natural jaw movements. Once the earwax reaches the end of the ear, it simply falls out.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/424964/original/file-20211006-14-1xe7qte.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/424964/original/file-20211006-14-1xe7qte.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=429&fit=crop&dpr=1 600w, https://images.theconversation.com/files/424964/original/file-20211006-14-1xe7qte.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=429&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/424964/original/file-20211006-14-1xe7qte.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=429&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/424964/original/file-20211006-14-1xe7qte.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=539&fit=crop&dpr=1 754w, https://images.theconversation.com/files/424964/original/file-20211006-14-1xe7qte.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=539&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/424964/original/file-20211006-14-1xe7qte.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=539&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">We are using earphones more and more each year, but listening for how long is too long?</span>
<span class="attribution"><span class="source">Christian Moro / Author Provided</span></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-how-do-scabs-form-151586">Curious Kids: how do scabs form?</a>
</strong>
</em>
</p>
<hr>
<h2>How earphones might affect this system</h2>
<p>The ear is self-cleaning and best performs its function without interruption. However, anything that blocks the normal progression of earwax moving outside can cause issues. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/425368/original/file-20211008-17-13724qc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Man holds model of ear" src="https://images.theconversation.com/files/425368/original/file-20211008-17-13724qc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/425368/original/file-20211008-17-13724qc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/425368/original/file-20211008-17-13724qc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/425368/original/file-20211008-17-13724qc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/425368/original/file-20211008-17-13724qc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/425368/original/file-20211008-17-13724qc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/425368/original/file-20211008-17-13724qc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The outer ear, where wax is produced, extends inside the body.</span>
<span class="attribution"><a class="source" href="https://image.shutterstock.com/image-photo/man-holding-model-human-inner-260nw-1349291441.jpg">Shutterstock</a></span>
</figcaption>
</figure>
<p>Normal use of in-ear devices <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4704552/">don’t often</a> cause a problem. But prolonged earphone use, such as if you leave them in all day, could:</p>
<ul>
<li> compress the earwax, making it less fluid and harder for the body to naturally <a href="https://pubmed.ncbi.nlm.nih.gov/30277727/">expel</a></li>
<li> compact the earwax to the extent the body induces inflammation. This results in white blood cells migrating to the area, increasing the number of cells in the <a href="https://www.aafp.org/afp/2007/0515/p1523.html">blockage</a></li>
<li> impact air flow and stop wet earwax drying out. When earwax retains its stickiness for prolonged periods of time, it encourages build-up</li>
<li> trap sweat and moisture in the ears, making them more prone to bacterial and fungal <a href="https://journals.lww.com/thehearingjournal/fulltext/2010/03000/how_to_care_for_moist_ears.12.aspx">infections</a></li>
<li> create a barrier to the earwax’s natural expulsion, which ends up stimulating the secretory glands and increasing <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4311346/">earwax production</a></li>
<li> reduce overall ear hygeine, if the pads of the earbuds are not cleaned properly, or <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8335768/">contaminated</a> with bacteria or infectious agents</li>
<li>damage your <a href="https://www.abc.net.au/news/2018-06-06/headphones-could-be-causing-permanent-hearing-damage/9826294">hearing</a> if the volume is set too high.</li>
</ul>
<p>If the build-up accumulates, excessive earwax can cause <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4356173/">hearing problems</a>, along with other symptoms such as pain, dizziness, tinnitus, itching, and vertigo. </p>
<p>If you need to listen for a prolonged period of time, using over-ear headphones may help a little. These offer a small amount of <a href="https://www.wellandgood.com/do-headphones-increase-ear-wax/">extra airflow</a> compared to the in-ear earphones and earbuds. However, this is not as good as leaving the ears open to the outside air, and an accumulation of earwax can still occur.</p>
<p>As they sit outside the ear canal, over-ear headphones are also less likely to cause any earwax compaction, or introduce bacteria or pathogens to the ear canal. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/health-check-is-it-bad-to-regularly-sleep-wearing-earplugs-60374">Health Check: is it bad to regularly sleep wearing earplugs?</a>
</strong>
</em>
</p>
<hr>
<h2>Nothing smaller than your elbow</h2>
<p>In most cases, the best way to control earwax is to <a href="https://www.scientificamerican.com/article/the-dangers-of-excessive-earwax/">leave it alone</a>. It is not recommended to use cotton buds frequently, as this can force earwax back into the ear canal. The longstanding <a href="https://www.ncbi.nlm.nih.gov/books/NBK2333/">advice</a> is not to put anything smaller than your elbow in your ear – in other words, don’t put anything in there! </p>
<p>Some traditional methods, such as olive oil drops or ear candles, may also have adverse effects and are not helpful.</p>
<p>If your have ear wax or related hearing concerns, your family doctor will have a range of treatment options to assist, and can also direct you to the correct health service if it requires longer-term management. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/425367/original/file-20211008-17-3xq6pq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="ear exam" src="https://images.theconversation.com/files/425367/original/file-20211008-17-3xq6pq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/425367/original/file-20211008-17-3xq6pq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/425367/original/file-20211008-17-3xq6pq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/425367/original/file-20211008-17-3xq6pq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/425367/original/file-20211008-17-3xq6pq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/425367/original/file-20211008-17-3xq6pq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/425367/original/file-20211008-17-3xq6pq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An otoscope helps visualise any wax build up in the ear.</span>
<span class="attribution"><a class="source" href="https://image.shutterstock.com/image-photo/closeup-female-doctor-examining-patients-260nw-1678999573.jpg">Shutterstock</a></span>
</figcaption>
</figure>
<p>Initially, they will look into your ear with a special instrument (otoscope) and see the extent of any blockage or <a href="https://www.mayoclinic.org/diseases-conditions/earwax-blockage/diagnosis-treatment/drc-20353007">dysfunction</a>.</p>
<p>In the meantime, the ear has a wonderful process of self-cleaning, and we should do our best to let this occur naturally. In most cases earphones are fine, but it might still be helpful to stay aware of how long you spend wearing them. Finally, be sure to always keep the volume at safe levels.</p><img src="https://counter.theconversation.com/content/168742/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Wireless earphones have freed us from devices. It’s tempting to wear them all day for phone calls, podcasts and music but research into hearing aids suggests this can create a sticky problem.Charlotte Phelps, PhD Student, Bond UniversityChristian Moro, Associate Professor of Science & Medicine, Bond UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1393922020-06-03T20:12:27Z2020-06-03T20:12:27ZAre your kids using headphones more during the pandemic? Here’s how to protect their ears<figure><img src="https://images.theconversation.com/files/339082/original/file-20200602-95028-2bh8sl.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C7360%2C4912&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>During the coronavirus pandemic, have your kids been using headphones more than usual? Maybe for remote schooling, video chats with relatives, or for their favourite music and Netflix shows?</p>
<p>We have to be careful about both the volume and duration of headphone use. Listening too loudly or for too long can do permanent damage to hearing. The good news is there are ways to prevent long-term harm relatively easily.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/5-reasons-its-safe-for-kids-to-go-back-to-school-137064">5 reasons it's safe for kids to go back to school</a>
</strong>
</em>
</p>
<hr>
<h2>Hearing loss in children may be increasing</h2>
<p>Our hearing needs to be protected throughout life, because damage to hearing cannot be reversed. This is why we have workplace noise exposure <a href="https://www.worksafe.vic.gov.au/noise-safety-basics">standards and guidelines</a>, which tell workers when to use protection such as earplugs or ear defenders.</p>
<p>Unfortunately though, hearing loss in children may be increasing. A <a href="https://pubmed.ncbi.nlm.nih.gov/30872125/?from_single_result=Prevalence+of+Childhood+Hearing+Loss+and+Secular+Trends%3A+A+Systematic+Review+and+Meta-Analysis&expanded_search_query=Prevalence+of+Childhood+Hearing+Loss+and+Secular+Trends%3A+A+Systematic+Review+and+Meta-Analysis">study</a> from last year, in which both of us were involved, reviewed the hearing of more than 3.3 million children from 39 countries across a 20-year period.</p>
<p>We found around 13% of children had measurable hearing loss by 18 years of age that may impact their ability to decipher sounds important for understanding speech. The study suggested hearing loss in kids is rising – but we don’t yet know why. </p>
<p>Not many studies have examined whether headphone use is directly linked to hearing loss in children. But in one <a href="https://jamanetwork.com/journals/jamaotolaryngology/article-abstract/2684510">study of 9-11-year-old Dutch children</a>, where 14% had measurable hearing loss, around 40% reported using portable music devices with headphones. Could headphones be contributing? Possibly, but unfortunately we don’t know for sure, and more studies are needed.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/339083/original/file-20200602-95054-ikzvos.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/339083/original/file-20200602-95054-ikzvos.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/339083/original/file-20200602-95054-ikzvos.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/339083/original/file-20200602-95054-ikzvos.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/339083/original/file-20200602-95054-ikzvos.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/339083/original/file-20200602-95054-ikzvos.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/339083/original/file-20200602-95054-ikzvos.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">More studies are needed to determine if headphone use is causing a decline in kids’ hearing. But there are ways to mitigate the risks regardless.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>How do we know whether our children’s hearing is being affected?</h2>
<p>Adults typically first notice a hearing problem by struggling to hear higher-pitched sounds clearly. Sounds may seem muffled, or the ears may feel “blocked”, or they may notice a ringing or buzzing sound, called tinnitus.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/even-mild-hearing-loss-as-a-child-can-have-long-term-effects-on-how-the-brain-processes-sound-125149">Even mild hearing loss as a child can have long-term effects on how the brain processes sound</a>
</strong>
</em>
</p>
<hr>
<p>Unlike adults, children won’t necessarily know how to describe these symptoms. Instead they may use terms they do know, like a bee buzzing, a whistle, or the wind blowing. Parents should treat any reported ear symptom as serious and get their child’s hearing tested. It’s best to visit a hearing clinic first, and then a GP if necessary, although this will depend on your location.</p>
<h2>Excessive noise damages hearing</h2>
<p>Our inner ear (cochlea) contains tiny hair cells, which change sounds we hear into electrical signals for our brain. These hair cells are finely tuned and are responsible for different pitches of sound, like keys on a piano. </p>
<p>Exposure to loud noise can damage these hair cells and perhaps the <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2812055/">nerve</a> that connects the cochlea to the brain. Repeated excessive noise exposure can lead to permanent hearing loss. Unfortunately, by the time someone experiences hearing problems, some irreversible damage has already happened.</p>
<h2>What should we do to protect kids’ hearing?</h2>
<p>The risk of hearing damage depends on both loudness and duration of sound exposure. Limiting both helps to reduce the risk of hearing damage.</p>
<h3>Limiting loudness</h3>
<p>We measure the loudness of sound in decibels (dB). But it’s important to note that the dB scale is logarithmic rather than linear. That means a 110dB sound (similar to a chainsaw) is actually much more than 10% louder than a 100dB sound. Parents can download free sound meter apps that help with understanding the volume of different environments and activities.</p>
<p>A more difficult task for parents is monitoring the loudness within their children’s headphones. Some headphones leak sounds out, while others insulate the sound into the ear. So a child using “leaky” headphones at a safe volume may appear to be listening to sounds that are too loud, but a child with tightly sealed headphones could be playing sounds at potentially damaging levels without parents noticing.</p>
<p>To understand their child’s specific usage, parents can: </p>
<ul>
<li><p><strong>listen to their child’s headphones</strong> to understand how loud sounds can become</p></li>
<li><p>check to see if children can <strong>hear you talk at a normal volume from an arm’s length away</strong>, over the sounds playing on the headphones. If they can, their headphone use is more likely to be at a safe volume. </p></li>
</ul>
<p>There are headphones designed for children that limit the maximum loudness – usually to 85dB. While a limit is great, listening to 85dB sounds all day every day is not risk-free. </p>
<p>Noise-cancelling headphones are another option, albeit expensive. By reducing the intrusion of outside noise, it should mean children can keep headphone volume lower.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/339088/original/file-20200602-95049-xdpotw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/339088/original/file-20200602-95049-xdpotw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/339088/original/file-20200602-95049-xdpotw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/339088/original/file-20200602-95049-xdpotw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/339088/original/file-20200602-95049-xdpotw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/339088/original/file-20200602-95049-xdpotw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/339088/original/file-20200602-95049-xdpotw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Parents can limit the loudness of headphones, as well as the duration of time spent listening with headphones.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h3>Managing duration</h3>
<p>We should also monitor how long we’re exposed to sound. Everyday conversation is around 60dB, which will not be a problem regardless of the duration of exposure. However, <a href="http://dangerousdecibels.org/education/information-center/decibel-exposure-time-guidelines/">guidelines</a> say we can be exposed an 85dB sound (like a rubbish truck) for up to 8 hours at a time. But if the loudness of the sound is increased by just 3 decibels to 88dB, the sound energy is doubled, and safe exposure time would drop to just 4 hours. Operating a chainsaw at 110dB would then be limited to around 1 minute before damage is likely to occur.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/tinnitus-scale-of-hearing-damage-for-music-industry-workers-revealed-127373">Tinnitus: scale of hearing damage for music industry workers revealed</a>
</strong>
</em>
</p>
<hr>
<p>Exposure to noise is cumulative. Noise can also come from other sources in the child’s environment. Consider a child’s activities throughout a day. Parents should try to avoid consecutive noisy exercises, like headphone use, music practice, then noisy toys or games. Considering the total “doses” of sound in the day means parents should schedule some breaks to allow the ears time to recover.</p>
<p>Of course, parents should practise what they preach! Modelling responsible use of headphones and awareness of the enjoyment of being able to hear well into adulthood is key.</p>
<hr>
<p><em>This article is supported by the <a href="https://theconversation.com/au/partners/judith-neilson-institute">Judith Neilson Institute for Journalism and Ideas</a>.</em></p><img src="https://counter.theconversation.com/content/139392/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Peter Carew has previously received funding that originated from the NHMRC. </span></em></p><p class="fine-print"><em><span>Valerie Sung receives funding from the National Health and Medical Research Council, the L'Oreal-UNESCO For Women In Science Fellowship, the Garnett Passe and Rodney Williams Memorial Foundation, the Royal Children's Hospital Foundation, the University of Melbourne Stevenson Chair of Paediatrics Strategic Support, the Murdoch Children's Research Institute, and previously received funding from the Royal Australasian College of Physicians Cottrell Research Establishment Fellowship and the Equity Trustees Charitable Trusts.</span></em></p>Listening with the volume too high or for too long can cause permanent hearing loss, but there are ways we can minimise the risks.Peter Carew, Lecturer, The University of MelbourneValerie Sung, Paediatrician, Senior Research Fellow, Honorary Clinical Associate Professor, Murdoch Children's Research InstituteLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/972592018-06-05T20:06:30Z2018-06-05T20:06:30ZCurious Kids: Why do our ears pop?<figure><img src="https://images.theconversation.com/files/220890/original/file-20180530-80658-1flw0o7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">You may need to pop your ears by yawning when you go up in a plane.</span> </figcaption></figure><p><em>This is an article from <a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a>, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky!</em> </p>
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<blockquote>
<p><strong>Hi Curious Kids, My name is James and I live in Melbourne and I’m 10 years old. Why do our ears pop when we reach a certain altitude? - James, age 10, Melbourne.</strong></p>
</blockquote>
<hr>
<p>Hi James. What a great question. </p>
<p>There are three key sections of our ear – the outer ear, the middle ear and the inner ear. Your question relates to the middle ear and the area around the ear drum. </p>
<p>The middle ear space is pretty airtight, although air can pass into and out of this space by the opening and closing of the Eustachian tube (the tube that links the middle ear to the back of the throat). Most of us can do this by yawning or opening our jaws, which often results in our ears “popping”. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/220888/original/file-20180530-80629-152tp8d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/220888/original/file-20180530-80629-152tp8d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/220888/original/file-20180530-80629-152tp8d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=523&fit=crop&dpr=1 600w, https://images.theconversation.com/files/220888/original/file-20180530-80629-152tp8d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=523&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/220888/original/file-20180530-80629-152tp8d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=523&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/220888/original/file-20180530-80629-152tp8d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=658&fit=crop&dpr=1 754w, https://images.theconversation.com/files/220888/original/file-20180530-80629-152tp8d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=658&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/220888/original/file-20180530-80629-152tp8d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=658&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Can you ‘pop’ your ears by yawning? It’s all about the Eustachian tube.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/">Shutterstock</a></span>
</figcaption>
</figure>
<p>Your ears pop because of the pressure difference between the air outside and the air inside your middle ear space. I’ll explain how that works.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-how-does-an-echidna-breathe-when-digging-through-solid-earth-96276">Curious Kids: How does an echidna breathe when digging through solid earth?</a>
</strong>
</em>
</p>
<hr>
<p>You have a small amount of air sealed in the middle ear space. And then there’s all the rest of the air outside, in the atmosphere. </p>
<p>Normally the air pressure inside the middle ear and in the atmosphere are very similar, or at least not different enough to cause you any trouble. As you increase in altitude (either in a car going up a hill, going up in a lift, or taking off in an aeroplane) the air pressure in the atmosphere decreases, making the air “thinner”, while the air pressure in the middle ear remains relatively unchanged. </p>
<p>This puts pressure on your eardrum as the air pressure in the middle ear expands relative to the air around it. This expansion causes not only the discomfort you feel before your ears “pop”, but also makes it harder to hear things, because the pressure on your eardrums makes the sound harder to transmit.</p>
<p>There is no specific altitude at which your ears pop, and during quick ascents, like during an aeroplane take-off, you may have to equalise or “pop” your ears a few times to keep up with the pressure changes.</p>
<p>Other times, like on a slow walk up a hill, your ears may equalise themselves without you even noticing. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-where-does-money-come-from-73598">Curious Kids: where does money come from?</a>
</strong>
</em>
</p>
<hr>
<p>The reverse can happen when you are descending in an aeroplane or going down a hill. The air in the atmosphere increases in density through the descent, while the air pressure in the middle ear space remains low like it was at the higher altitude. </p>
<p>This forces pressure on the eardrum and causes it to retract inwards (instead of bulging outwards on ascent) until your ears pop to make the pressure between the middle ear and the atmosphere more equal.</p>
<p>You can have some trouble if you are doing a significant ascent or descent and have a cold or an ear infection.</p>
<p>The mucus from a cold or ear infection can block the Eustachian tube, making it hard to equalise your ears properly. This can make your ears ache from even small changes in altitude and the eardrum is pushed inwards (on descent) or outwards (on ascent).</p>
<p>Babies and young children often have blocked Eustachian tubes – this may be one reason they don’t like flying.</p>
<hr>
<p><em>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. They can:</em></p>
<p><em>* Email your question to curiouskids@theconversation.edu.au
<br>
* Tell us on <a href="https://twitter.com/ConversationEDU">Twitter</a></em></p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p><em>Please tell us your name, age and which city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question but we will do our best.</em></p><img src="https://counter.theconversation.com/content/97259/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chris Brennan-Jones receives research funding from the NHMRC and the Western Australian Department of Health.</span></em></p>Listen up. Today we’re hearing all about why your ears pop when you go up, up, up and away.Chris Brennan-Jones, NHMRC Research Fellow, Telethon Kids Institute, The University of Western AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/838782017-10-17T19:14:04Z2017-10-17T19:14:04ZCurious Kids: Why do so many animals seem to have pink ears, when their bodies are all different colours?<figure><img src="https://images.theconversation.com/files/189115/original/file-20171006-25758-1c0w700.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">It's all about evolution.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/myri_bonnie/33391930610/in/photolist-SSJnBy-7TWWNH-29W1uY-EYyRkm-67Aacv-SfjvRu-eudyTt-ciM6oA-4AXH5c-6gLcJm-6SpLdQ-4MtHzu-5H1Gfg-pEcRAA-7D7BQf-rcxc3R-nwckMa-9NqfJQ-4SzfEs-K1MkD-9q5hyu-4QKVCY-6h1ese-6TJCrD-QuUUi-LLBVx-6YMcwE-7cSkm7-7SphNB-2tBjBz-cddhR7-81nDzN-6JJ4T5-3emTo-LiTzt-6r7Fa8-9FnCxM-7Z27tv-6WsYcV-aHHwcx-5mtcpD-bdJD6r-7Jie6R-4w5YNu-7KA4Hn-6gG2Yr-6p4U1d-57dkhg-6oZWzX-eh2keR">Flickr/myri_bonnie</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p><em>This is an article from <a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a>, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky!</em> </p>
<hr>
<blockquote>
<p><strong>Why do so many animals seem to have pink ears, when their bodies are all different colours? – Heather, age 8, Brisbane.</strong> </p>
</blockquote>
<hr>
<p>Interesting question, Heather.</p>
<p>The short answer is that ears have a lot of blood vessels near the skin, which is pretty thin in that spot. Having blood vessels close to the skin helps animals – including you and me – to keep their body temperature just right.</p>
<p>Animals that evolved in cold parts of the world usually have lighter skin. If a light-skinned animal has blood vessels close to the surface of their ear skin, this will make the ears look pink.</p>
<p>But the truth is that most animals actually don’t have pink ears. Let us explain.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/SKIzT2bMfXI?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
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<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-how-do-satellites-get-back-to-earth-82447">Curious Kids: How do satellites get back to Earth?</a>
</strong>
</em>
</p>
<hr>
<h2>Evolution gave us different ear shapes and colours</h2>
<p>You’ve probably heard of evolution. That’s where animals change their appearance, how they hunt (or how they’re hunted) and how they attract their mates. All of these changes and adaptations improve their chances of survival.</p>
<p>Evolution helped influence skin colour in animals as well. </p>
<p>Near the equator, where the climate is hot, animals tend to have darker skin, including on their ears. Think of the African elephant, which has quite dark ears (they also have the biggest ears of any animal on the planet).</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/189102/original/file-20171006-25772-15h1iqw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/189102/original/file-20171006-25772-15h1iqw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/189102/original/file-20171006-25772-15h1iqw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/189102/original/file-20171006-25772-15h1iqw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/189102/original/file-20171006-25772-15h1iqw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/189102/original/file-20171006-25772-15h1iqw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/189102/original/file-20171006-25772-15h1iqw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Animals in hot climates often have darker skin.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/birdbrian/33562574320/in/photolist-T8NY3u-W3yh8i-68vMQD-THRDMM-Twn7nv-TEfw2W-TwoKzV-Su1hKZ-Twn5VH-LTu8J-T8NYyQ-TwoUhK-Twn6DM-6hwaZq-qUP3bi-Su3KgF-7QjznT-zvvau-8EZX4D-Twn8XK-THRETp-XTYfUU-iggDgF-TwoPe8-TEfn69-Srkbdw-Su3HFX-TtYmcy-qFcsFT-6k5aF6-nzCzJB-94me8S-58tm3A-dF5pDB-94iezZ-2PGETV-58p9WB-94mkjW-58tmQu-2PGBgi-a2s9ws-oSapQX-2PM1xS-94mbim-cPRo2Q-XjQigQ-2MRX2Z-oa9rFG-TEhCZ9-Su3CkB">Flickr/Brian Ralphs</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>In colder climates, skin colour is usually lighter and often pink. This is true for humans too. The skin colour (and ear colour) of early humans became lighter as they migrated out of Africa into colder regions.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/189110/original/file-20171006-25772-t7flxn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/189110/original/file-20171006-25772-t7flxn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/189110/original/file-20171006-25772-t7flxn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/189110/original/file-20171006-25772-t7flxn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/189110/original/file-20171006-25772-t7flxn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/189110/original/file-20171006-25772-t7flxn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/189110/original/file-20171006-25772-t7flxn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/189110/original/file-20171006-25772-t7flxn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Many animals with light-coloured fur have light-coloured pinkish skin underneath.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/vmos/1337535118/in/photolist-33cdAj-phGWXL-8fvkai-dLFnPi-6tXugh-dU9YKU-ecJ1hs-hHEem5-Y7GzDx-4jLpTK-9PEZut-Jk7NcQ-ebVjcH-gx5nd2-qRh8a5-5j2JCn-HDnaT-5AzmSc-hHCWpu-5kZYkH-dPqU2T-hHDd56-nerV6H-roYc1S-pYkKJt-8Apn58-p4nhSR-5iJmAB-5m5diY-hHCY3j-5iNxMC-Fzni6A-7GegfX-JS1XwX-hHCtgU-599D7J-5uLgmQ-6EhfvY-hHEYnc-ek8AbY-w6Whm-9yDHT4-WG6amV-95y3SH-5CSa8p-a5Qhnt-d3mqsd-4AWykj-qVT68T-7LRMZS">Flickr/J</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Why is skin colour different in different climates? Skin pigmentation, which is what gives skin its colour, can protect against sunburn and skin cancer. When animals live in colder, more overcast parts of the world they don’t need this pigmentation as much to survive. Light-coloured skin also helps animals stay warmer because it reduces heat loss, which is handy if you’re in a colder climate.</p>
<p>You mention, correctly, that animals can have bodies of all sorts of colours, but still have pink ears.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-what-happens-if-a-venomous-snake-bites-another-snake-of-the-same-species-81564">Curious Kids: What happens if a venomous snake bites another snake of the same species?</a>
</strong>
</em>
</p>
<hr>
<p>For most species, the colour of their fur, feathers or other body covering has generally evolved as camouflage. That allows animals to blend into the background and avoid being eaten, or for predators to remain hidden during hunting. One example is the sandy-coloured coat of the desert fennec fox. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/189111/original/file-20171006-25772-99wph.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/189111/original/file-20171006-25772-99wph.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/189111/original/file-20171006-25772-99wph.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=447&fit=crop&dpr=1 600w, https://images.theconversation.com/files/189111/original/file-20171006-25772-99wph.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=447&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/189111/original/file-20171006-25772-99wph.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=447&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/189111/original/file-20171006-25772-99wph.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=561&fit=crop&dpr=1 754w, https://images.theconversation.com/files/189111/original/file-20171006-25772-99wph.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=561&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/189111/original/file-20171006-25772-99wph.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=561&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The fennec fox has sandy-coloured fur and large ears.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/nathaninsandiego/24650682516/in/photolist-Dyic6w-DEnB2y-6m5DvT-mL21De-8mHSGy-m7k5Jv-m7kH4n-jHdRYh-9vsv87-bddQHr-9A9cco-qFRrSt-dVCFih-bUTg54-f9FHAx-dLunLC-9MMgXY-AwnSBF-bUTg5a-7WYVu1-jKZPgv-ihQWG-6zCU4X-dL32SC-f3tjLZ-au2RmC-qfsWq-DqcPKQ-bjBLJn-51bMcQ-9Vn7tf-9u6fBB-6MUMBr-5jbx8M-6WHgEc-7HTPnn-6WHgtc-NZKuz-5vCVer-dL328m-UsXgQR-oVnbTf-bwzze4-dKuCb7-8jbn2y-oRE4Td-q5oBGC-f8bvR-BEuPGu-f89Py">Flickr/Nathan Rupert</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Like ear colour and size, body colour also helps animals keep their body temperature at just the right level.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/189112/original/file-20171006-25792-4umxgq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/189112/original/file-20171006-25792-4umxgq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/189112/original/file-20171006-25792-4umxgq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=905&fit=crop&dpr=1 600w, https://images.theconversation.com/files/189112/original/file-20171006-25792-4umxgq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=905&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/189112/original/file-20171006-25792-4umxgq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=905&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/189112/original/file-20171006-25792-4umxgq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1137&fit=crop&dpr=1 754w, https://images.theconversation.com/files/189112/original/file-20171006-25792-4umxgq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1137&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/189112/original/file-20171006-25792-4umxgq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1137&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The serval, a type of African wildcat, has evolved large ears that help it hear better.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/bfra07/5695544337/in/photolist-9Fi9Ui-7YEZaL-7YBLJ6-byxHan-a54RnM-6URnQW-a54Rpv-dH6Yk3-7YBLfx-7YEZAm-9u9jFQ-a54Rmx-a54Rqr-52keA7-fSLdV-a54Rkr-7YEZSq-scStt8-8seARa-5BC5jw-85cWQS-ceupuf-eih2XV-eih2mT-ayjWaQ-8deWuM-qy8v1H-eih32e-SrEGuy-qRNeno-bGLWUP-einL37-5v7TUJ-9bxcv8-scQ4HT-8gjGfM-p6R27G-ijdHP9-einLKY-einLTh-einL9A-9YL4fw-einLQb-eih2z2-eih2t4-einLHL-einLBQ-nrdW7w-8TsPX5-yi2VJ">Flickr/Brad</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>But even when animals have feathers, scales or fur that is brown, orange, white or any number of colours, they might have skin underneath that is light-coloured.</p>
<p>And when you get ears that don’t have much fur or feathers, you’ll see that light-coloured skin looks pink because of the blood vessels that are close to the surface in the ear area.</p>
<h2>Ear shapes and sizes</h2>
<p>In many animals, ears come in many different shapes and sizes. </p>
<p>For example, in bats, the serval (a type of African wildcat) and the fennec fox, the ears are large compared to their body size – this helps them hear better because it allows them to detect more sound waves.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/189113/original/file-20171006-25772-1xi5v60.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/189113/original/file-20171006-25772-1xi5v60.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/189113/original/file-20171006-25772-1xi5v60.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=463&fit=crop&dpr=1 600w, https://images.theconversation.com/files/189113/original/file-20171006-25772-1xi5v60.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=463&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/189113/original/file-20171006-25772-1xi5v60.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=463&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/189113/original/file-20171006-25772-1xi5v60.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=582&fit=crop&dpr=1 754w, https://images.theconversation.com/files/189113/original/file-20171006-25772-1xi5v60.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=582&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/189113/original/file-20171006-25772-1xi5v60.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=582&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Naked mole-rats have tiny ears because they need to dig a lot. Big ears would get in the way.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/riussi/54718701/in/photolist-5QrXT-9zpcG3-2k68Zk-cvNVyC-58jEbx-89u2Kr-8Dgd1V-6EPrc7-dbEC3L-3LQK6u-f6KPBu-4UfJd7-bCJYR-4JaZ5e-pP7Q4J-ajb7EB-aRzyNP-dF9uFW-f6KRMA-2ALEo-92TLDn-iMWga-awWFhM-cEbYd5-75GH3-92TLDg-7ZzbUq-6dBXx8-8DjjTG-a6B481-89xh2W-cF8yau-awZo8C-awZnM7-awWERP-awZo5G-awWEBD-awZob1-awZnJG-8DgeJr-awZnAu-awWFfg-89xmrA-a8ZyJ8-2ALEp-aib5K6-gAiye-awZnGG-awZnv3-6XLvjV">Flickr/Juha Ristolainen</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>These creatures, and other animals with large ears, have excellent hearing, especially at night when many are active. </p>
<p>In contrast, the naked mole-rat has very small ears because it needs to burrow a lot – big ears would get in the way of their digging, so it’s not worth it. </p>
<p>The other downside of big ears is that you can lose a lot of body heat. That’s why animals that live in really cold places, like the Arctic fox, have quite small ears.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/189114/original/file-20171006-25772-1hde7s1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/189114/original/file-20171006-25772-1hde7s1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/189114/original/file-20171006-25772-1hde7s1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/189114/original/file-20171006-25772-1hde7s1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/189114/original/file-20171006-25772-1hde7s1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/189114/original/file-20171006-25772-1hde7s1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/189114/original/file-20171006-25772-1hde7s1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/189114/original/file-20171006-25772-1hde7s1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Arctic fox has really small ears, to help reduce heat loss.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/dmongrain/6897386531/in/photolist-bvuUHr-bq7Wh4-dMgP9V-e5urjK-rb3eMx-bmPoV3-hh2WrW-eeiPSY-wxwfA-jfjbZC-9kf3Aa-m1YfNv-bLmWsT-rosFAq-dVJgfU-9boYLX-dBHfa9-Bkhrm7-5d3tfP-BSf4qu-98mYn6-e9s5LH-q97kQm-e3Rk3Z-ej1MPP-k2PQEt-iEkuFj-4uVg7W-aCqyqh-9jNdN3-4u9LP1-b5yXg2-dtQacT-dtQaez-E8osGy-adktAn-5Uyh4t-D8t3Bd-k87cqH-AphQRH-CGaLS1-7J3pKm-rpDHNc-DcZk3C-dYRqJg-FRiZkL-j9ZHyu-6uKEBM-7HYmdt-t2JR8d">Flickr/Dan Mongrain</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<hr>
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<img alt="" src="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p><em>Please tell us your name, age and which city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question but we will do our best.</em></p><img src="https://counter.theconversation.com/content/83878/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Wayne Davies is supported by Future Fellowship and Discovery Project grants awarded by the Australian Research Council (FT110100176 and DP140102117). </span></em></p><p class="fine-print"><em><span>Shaun Collin receives funding from the Australian Research Council. </span></em></p>Animals that evolved in cold parts of the world usually have lighter skin. If a light-skinned animal has blood vessels close to the surface of their ear skin, this will make the ears look pink.Wayne Iwan Lee Davies, Adjunct Research Fellow, School of Biological Sciences, The University of Western AustraliaShaun Collin, Winthrop Professor/WA Premier's Research Fellow, School of Biological Sciences and the Oceans Institute, The University of Western AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/735322017-03-01T15:00:39Z2017-03-01T15:00:39ZDeafness carries a huge cost burden: economic as well as personal<figure><img src="https://images.theconversation.com/files/158545/original/image-20170227-26340-1g7inox.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Deafness often <a href="https://www.researchgate.net/publication/7064756_Audiology_in_South_Africa">remains invisible</a>, especially in contexts of constrained resources and poverty. It can exact a <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4007124/">high cost</a> for both developed and developing countries because it has a significant impact on the lives of those affected, and the economies of the countries in which they live. Also, the services for people who are deaf can be very expensive.</p>
<p>By some estimates hearing loss costs economies <a href="http://www.who.int/mediacentre/factsheets/fs300/en/">US$750 billion</a> globally each year. The economic implications <a href="http://hearinghealthmatters.org/betterhearingconsumer/2011/how-much-does-my-hearing-loss-cost-me/">have been measured</a> by looking at the impact of late diagnosis, undiagnosed deafness, insidious deafness, the impact on employment, and the lack of employment opportunities because of deafness. </p>
<p>Countries with the lowest gross national income per capita have the highest numbers of children who are deaf. There are an estimated <a href="http://www.who.int/mediacentre/factsheets/fs300/en/">32 million deaf children </a> in the world. <a href="http://www.paho.org/hq/index.php?option=com_content&view=article&id=9345%3A2014-many-countries-lack-capacity-prevent-treat-hearing-loss&catid=1443%3Aweb-bulletins&Itemid=135&lang=fr">Most</a> live in South Asia, Asia Pacific and sub-Saharan Africa.</p>
<p>According to the World Health Organisation there are about <a href="http://www.who.int/pbd/deafness/WHO_GE_HL.pdf">6.8 million</a> children whose deafness is considered disabling in sub-Saharan Africa. The figure is <a href="http://www.who.int/pbd/deafness/WHO_GE_HL.pdf">0.8 million</a> in high income countries.</p>
<p>The focus of <a href="http://www.who.int/pbd/deafness/world-hearing-day/2017/en/">World Hearing Day</a> in 2017 draws attention to the economic impact of deafness in its tagline, “<a href="https://www.actiononhearingloss.org.uk/">Action for hearing loss</a>: makes a sound investment”. Economic considerations are important because they <a href="http://www.wwhearing.org/impact">drive the support</a> and resources available for people with deafness.</p>
<p>There are various <a href="http://www.who.int/pbd/deafness/world-hearing-day/WHD2017Brochure.pdf?ua=1">interventions</a> available to address hearing loss. These include <a href="http://www.cochlear.com/wps/wcm/connect/au/home/understand/hearing-and-hl/hl-treatments/cochlear-implant">cochlear implants</a>, <a href="http://www.mayoclinic.org/diseases-conditions/hearing-loss/in-depth/hearing-aids/art-20044116">hearing aids</a>and learning <a href="http://www.handspeak.com/study/index.php?id=1">sign language</a>. But in many resource-constrained countries, it’s not always possible for people to access these.</p>
<p>For example, globally hearing aids reach one out of ten people who need them. In developing countries only about <a href="http://www.who.int/mediacentre/factsheets/fs300/en/index.html">one out of 40 people</a> who may want hearing aids get access to them.</p>
<p>A great deal more needs to be done in developing countries, particularly in sub-Saharan Africa, to tackle the problem. But governments need to take statistics and economic considerations into account during planning for activities that involve people who are deaf, the education of deaf children, and <a href="http://www.scielosp.org/scielo.php?script=sci_arttext&pid=S1020-49892001000800014">support services for people who are deaf</a>.</p>
<h2>Looking beyond the numbers</h2>
<p>As the example of hearing aids shows, economic limitations often result in people not receiving the level of support they need, even when their right to access is enshrined in legislation. </p>
<p>But while it’s important to plan for the costs related to deafness and to provide money for services and resources, the economic factors shouldn’t overshadow the human element. Service provision for deafness shouldn’t only happen to reduce costs. Deaf people deserve services because of their rights as people and because societies ought to strive for humanistic values in attending to people’s needs. </p>
<p>Another way of looking at the effect of deafness is to compare the years lost to disability attributed to deafness. These also differ dramatically between developed and developing countries. </p>
<p><a href="https://www.nimh.nih.gov/health/statistics/disability/what-are-ylds.shtml">Years lost to disability</a> can be described as years of “healthy” life lost by virtue of being in poor health or because of disability.</p>
<p>The WHO estimates that 232 million years are lost to deafness disability in developing countries compared with 4.2 million years in developed countries. </p>
<p>Africa has the highest number of years lost to disability to deafness and also has the greatest burden of disease compared to other regions in Europe, the Americas, and South East Asia.</p>
<p>The burden of disease is heavier in <a href="http://www.hear-it.org/children-and-hearing-loss">children</a> up to the age of four who contribute 31% in low and middle income countries. In high income countries this age group only contributes 5% towards the burden of disease.</p>
<h2>What is the way forward?</h2>
<p>While the issue of resources is vitally important, the issue of deafness shouldn’t simply by based on calculations of cost. As I’ve said, this focus is reductionist because it is directed at loss rather than analysing the entire human experience of deafness. </p>
<p>A valuation of human beings according to their functional capacity is in sharp contrast to the <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1117148/">humanistic values</a> laid down in the <a href="http://www.un.org/en/universal-declaration-human-rights/">Declaration of Human Rights</a>. </p>
<p>The adage goes, “money makes the world go round”. For many people who are deaf, that is indeed the case. The economic context determines their access to services and so there is the risk that deafness remains invisible. In forging a way forward, service provision for deaf people ought to prioritise their human value as a precursor to economic value.</p>
<p>The call is to remember the deaf person when looking at the general ledger entries so that the human experience of deafness is given the prominence it requires and merits. Yes, it is an idealistic suggestion – some would say lofty – but it is not an impossible one.</p><img src="https://counter.theconversation.com/content/73532/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Victor de Andrade received financial assistance from the University of the Witwatersrand for his PhD. He is affiliated with the University of the Witwatersrand, his place of employment, as well as with external organisations such as People for Disability Issues (PADI) and Polokong Children's Village. Victor has served as an advisor on the UN WHO Global Cooperation on Assistive Technology (GATE).</span></em></p>Deafness is a huge burden for economies and individuals. This is particularly true in developing countries. Solutions need to take into account not just costs, but the rights of individuals too.Victor de Andrade, Head - Audiology Division, Department of Speech Pathology & Audiology School of Human and Community Development, University of the WitwatersrandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/159842013-07-12T04:55:54Z2013-07-12T04:55:54ZBone conduction: the new front in guerilla advertising<figure><img src="https://images.theconversation.com/files/27306/original/9xxthzsp-1373519128.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Bone conduction technology enables commuters to hear advertisements via their skull – but how?</span> <span class="attribution"><span class="source">Mr.Fink's Finest Photos</span></span></figcaption></figure><p>Imagine this scenario: after a long day of work, you settle in a train seat, rest your head against the window and close your eyes for a well-earned nap - only instead of the soothing clickety-clack vibrations of the carriage, you hear a deep, jaunty voice - seemingly in your head - urging you to download an app.</p>
<p>Don’t worry - you (probably) aren’t losing your mind. You may have read last week German media company Sky Deutschland has been linked to a <a href="http://www.bbc.co.uk/news/technology-23167112">new advertising program</a> targeting train commuters. And while a new media source on trains may seem like no big deal in this digital age, there is something about this program that sets it apart. </p>
<p>The audio information of these ads is transmitted via the window of the train. When you rest your head against the glass the signal is heard inside your head, utilising a phenomenon known as <a href="http://en.wikipedia.org/wiki/Bone_conduction">bone conduction</a>. See some reactions to the technology in the video below:</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Z8g_SBzQFE8?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<h2>How does bone conduction work?</h2>
<p>Let’s think about how sound is detected. Humans perceive sound when particles vibrate in a frequency range that our ears are capable of detecting (between <a href="http://en.wikipedia.org/wiki/Hearing_range">20Hz and 20kHz</a>). Usually, when we talk about human hearing, we are referring to the vibration of air particles that the auditory system processes as sound. </p>
<p>If you’ve ever tried to listen to someone with your head under water you realise just how good air is at transmitting sound to the human ear compared to a substance like water. </p>
<p>The unusual thing about bone conduction is that the vibrating material is not air, but a solid object. Think about what happens when you lean your head against a train window: you can hear a myriad of sounds from the tracks and the carriage that your ears don’t pick up through the air. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/27293/original/j5xjzr4f-1373516290.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/27293/original/j5xjzr4f-1373516290.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/27293/original/j5xjzr4f-1373516290.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=471&fit=crop&dpr=1 600w, https://images.theconversation.com/files/27293/original/j5xjzr4f-1373516290.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=471&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/27293/original/j5xjzr4f-1373516290.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=471&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/27293/original/j5xjzr4f-1373516290.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=593&fit=crop&dpr=1 754w, https://images.theconversation.com/files/27293/original/j5xjzr4f-1373516290.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=593&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/27293/original/j5xjzr4f-1373516290.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=593&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The cochlea.</span>
<span class="attribution"><span class="source">wellcome images</span></span>
</figcaption>
</figure>
<p>This is because your <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/sound/cochlea.html">cochlea</a>, or hearing organ, is a bony structure coupled to the bones of your skull. When your head is placed against a vibrating object, like a train window, the vibration is transmitted directly to your cochlea through these skull bones.</p>
<p>Bone conduction assisted hearing isn’t anything particularly new. The technology is already used in <a href="http://en.wikipedia.org/wiki/Bone_anchored_hearing_aid">bone-anchored hearing aids</a>, <a href="http://news.cnet.com/8301-17938_105-57462412-1/new-aftershokz-bone-conduction-headphones-due-in-september/">swimmers’ headphones</a>, and will be used in the soon-to-be-released <a href="http://www.wired.co.uk/news/archive/2013-02/04/google-glass-bone-vibration">Google Glass</a>. But this appears to be its first time used in advertising.</p>
<h2>Can I escape it?</h2>
<p>You can, but you might have to say goodbye to your window-supported naps.</p>
<p>Earplugs will not be able to block out a bone conducted signal; in fact, they are more likely to enhance it. By sealing the ear canal with a plug, one becomes more vulnerable to the <a href="http://en.wikipedia.org/wiki/Occlusion_effect">occlusion effect</a>. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/27288/original/2933vk75-1373515391.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/27288/original/2933vk75-1373515391.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/27288/original/2933vk75-1373515391.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=733&fit=crop&dpr=1 600w, https://images.theconversation.com/files/27288/original/2933vk75-1373515391.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=733&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/27288/original/2933vk75-1373515391.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=733&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/27288/original/2933vk75-1373515391.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=921&fit=crop&dpr=1 754w, https://images.theconversation.com/files/27288/original/2933vk75-1373515391.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=921&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/27288/original/2933vk75-1373515391.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=921&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">kygp</span></span>
</figcaption>
</figure>
<p>To demonstrate the occlusion effect, block your ears completely and speak. Your voice sounds different because you are hearing a combination of the air and bone-conducted signal of your voice vibrating through your skull. </p>
<p>Using earphones would block most people’s ears enough to cause an occlusion effect, and this would make the bone conducted signal even more annoying to those commuters who did not wish to hear it. </p>
<p>Depending on the volume of the transmitted advertisement, it may be possible to block it out (or mask it) with music playing through earphones. However, if commuters are forced to increase the volume of their music players to cover up annoying advertisements, there is potential for that music to cause <a href="https://theconversation.com/mosquito-devices-may-be-used-to-disperse-australian-delinquents-but-how-do-they-work-14743">damage to their hearing</a>.</p>
<p>The only ways which you could actually avoid hearing these advertisements would be to rest your head on a dampening pillow, made of a material that would not transmit the vibration, or take your head off the window altogether. </p>
<p>If advertising campaigns like these were to become commonplace, napping on public transport may be a thing of the past. Enjoy them while you can!</p><img src="https://counter.theconversation.com/content/15984/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Catherine McMahon receives financial support from the HEARing CRC, established and supported under the Cooperative Research Centres Program – an initiative of the Australian Government. She is affiliated with ARC Centre of Excellence in Cognition and its Disorders (CCD).</span></em></p><p class="fine-print"><em><span>Phillip Nakad does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Imagine this scenario: after a long day of work, you settle in a train seat, rest your head against the window and close your eyes for a well-earned nap - only instead of the soothing clickety-clack vibrations…Catherine McMahon, Head of Audiology, Macquarie UniversityPhillip Nakad, Audiology Clinic Manager, Macquarie UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/147432013-06-02T20:28:53Z2013-06-02T20:28:53ZMosquito devices may be used to disperse Australian delinquents – but how do they work?<figure><img src="https://images.theconversation.com/files/24744/original/zxgvn4k3-1369965715.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Age-related hearing loss starts a lot earlier than you might think, and is exploited in anti-vandalism measures.</span> <span class="attribution"><span class="source">locomomo</span></span></figcaption></figure><p>You may have read last week that, in a bid to curb graffiti, Sydney’s State Rail may <a href="http://www.dailytelegraph.com.au/news/buzz-beats-graffiti-vandals/story-fni0cx4q-1226651709640">trial Mosquito devices</a> - technology that emits a high-pitched noise that’s audible only to people aged in their early twenties and younger - to drive away would-be vandals. A kind of teenager repellent, if you will.</p>
<p>Depending on your age, you can hear it, or not hear it, here:</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/AXhRmv1mrs4?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">What’s your hearing age?</span></figcaption>
</figure>
<p>The same technology has been used widely across Europe since 2006, and especially <a href="http://www.guardian.co.uk/society/2010/jun/20/teenager-repellent-mosquito-banned-europe">embraced in the UK</a>, despite calls for it to be banned as it’s <a href="http://assembly.coe.int/ASP/Doc/XrefViewHTML.asp?FileID=12727&Language=EN">claimed to violate</a> the European Court of Human Rights’ legislation prohibiting torture.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/24730/original/f82tvdcn-1369960532.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/24730/original/f82tvdcn-1369960532.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/24730/original/f82tvdcn-1369960532.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/24730/original/f82tvdcn-1369960532.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/24730/original/f82tvdcn-1369960532.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/24730/original/f82tvdcn-1369960532.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1006&fit=crop&dpr=1 754w, https://images.theconversation.com/files/24730/original/f82tvdcn-1369960532.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1006&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/24730/original/f82tvdcn-1369960532.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1006&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">tanakawho</span></span>
</figcaption>
</figure>
<p>Ethical aspects aside: how does the Mosquito, and other such devices, target such a specific subset of the population?</p>
<p>As we get older, permanent hearing loss is affected by environmental factors as well as the normal ageing process (known as <a href="http://www.nidcd.nih.gov/health/hearing/pages/presbycusis.aspx">presbycusis</a>). </p>
<p>Most commonly, hearing loss occurs in the higher frequencies first, gradually extending to the low frequencies as the magnitude of hearing loss increases. And it is the outer hair cells in the hearing organ, known as the <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/sound/cochlea.html">cochlea</a> (which looks a little bit like a snail shell), which are the most vulnerable to a variety of insults, including</p>
<ul>
<li><a href="http://www.ncbi.nlm.nih.gov/pubmed/4835178">loud noise</a></li>
<li><a href="http://www.ncbi.nlm.nih.gov/pubmed/8233489">drugs</a> that are toxic to the ear (such as salicylate which is found in aspirin and quinine found in some antimalarial drugs)</li>
<li>factors that affect ageing (such as <a href="http://www.karger.com/Article/Abstract/259195">reduced blood flow</a>)</li>
</ul>
<h2>Ear anatomy 101</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/24741/original/trfgjtmz-1369963435.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/24741/original/trfgjtmz-1369963435.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/24741/original/trfgjtmz-1369963435.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=455&fit=crop&dpr=1 600w, https://images.theconversation.com/files/24741/original/trfgjtmz-1369963435.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=455&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/24741/original/trfgjtmz-1369963435.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=455&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/24741/original/trfgjtmz-1369963435.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=572&fit=crop&dpr=1 754w, https://images.theconversation.com/files/24741/original/trfgjtmz-1369963435.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=572&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/24741/original/trfgjtmz-1369963435.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=572&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">Wikimedia Commons</span></span>
</figcaption>
</figure>
<p>A sound transmitted through air causes vibration of the eardrum that is transmitted to the cochlea via three small bones, known collectively as the <a href="http://audilab.bmed.mcgill.ca/%7Edaren/3Dear/mid1.html">ossicles</a>.</p>
<p>This sets up a travelling wave along a membrane in the cochlea, known as the <a href="http://147.162.36.50/cochlea/cochleapages/theory/bm/bm.htm">basilar membrane</a>, which progresses from the base of the cochlea towards the apex. The properties of the membrane gradually change from the base which is stiffer and narrower (and has less mass) to the apex where it is less stiff and wider (with more mass). </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/24737/original/382d3bnv-1369960898.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/24737/original/382d3bnv-1369960898.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/24737/original/382d3bnv-1369960898.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=480&fit=crop&dpr=1 600w, https://images.theconversation.com/files/24737/original/382d3bnv-1369960898.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=480&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/24737/original/382d3bnv-1369960898.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=480&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/24737/original/382d3bnv-1369960898.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=603&fit=crop&dpr=1 754w, https://images.theconversation.com/files/24737/original/382d3bnv-1369960898.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=603&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/24737/original/382d3bnv-1369960898.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=603&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A cross section of the cochlea.</span>
<span class="attribution"><span class="source">Wikimedia Commons</span></span>
</figcaption>
</figure>
<p>These changes in the membrane’s properties cause the membrane to be tuned like a piano (known as <a href="http://www.ncbi.nlm.nih.gov/pubmed/23055490">tonotopic tuning</a>), where high frequencies are located near the base and low frequencies near the apex.</p>
<p>A single row of inner hair cells and three rows of outer hair cells sit on top of this membrane. </p>
<p>These are known as “hair cells” because of the tiny hair-like projections that are located on the top of the cells known as <a href="http://www.d.umn.edu/%7Ejfitzake/Lectures/DMED/InnerEar/Transduction/TipLinks.html">stereocilia</a>. The cells move up and down with the vibration of the basilar membrane and the stereocilia are displaced side-to-side. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/24724/original/h3nrx69r-1369957133.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/24724/original/h3nrx69r-1369957133.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/24724/original/h3nrx69r-1369957133.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=443&fit=crop&dpr=1 600w, https://images.theconversation.com/files/24724/original/h3nrx69r-1369957133.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=443&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/24724/original/h3nrx69r-1369957133.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=443&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/24724/original/h3nrx69r-1369957133.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=556&fit=crop&dpr=1 754w, https://images.theconversation.com/files/24724/original/h3nrx69r-1369957133.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=556&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/24724/original/h3nrx69r-1369957133.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=556&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Hair cells of the inner ear.</span>
<span class="attribution"><span class="source">Wellcome Images</span></span>
</figcaption>
</figure>
<p>Inner hair cells, known as sensory cells, are responsible for the conversion of the basilar membrane vibration into an electrical impulse. Outer hair cells are known as motor cells and “twitch” in time with the vibration of the basilar membrane. </p>
<p>This amplifies the vibration at very discrete areas along the basilar membrane that are related to the frequency of sound presented and provides us with very good frequency discrimination. </p>
<p>We hear when the sound is converted from this mechanical vibration into an electrical impulse which travels up to the auditory part of the brain via the <a href="http://en.wikipedia.org/wiki/Cochlear_nerve">auditory nerve</a>.</p>
<h2>Say goodbye to high frequencies</h2>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/24745/original/vyr3t67y-1369967028.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/24745/original/vyr3t67y-1369967028.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/24745/original/vyr3t67y-1369967028.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/24745/original/vyr3t67y-1369967028.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/24745/original/vyr3t67y-1369967028.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/24745/original/vyr3t67y-1369967028.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/24745/original/vyr3t67y-1369967028.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/24745/original/vyr3t67y-1369967028.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption"></span>
<span class="attribution"><span class="source">purplemattfish</span></span>
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<p>It is the outer hair cells (and, in fact, the stereocilia) which are most physiologically vulnerable to damage. A complete loss of outer hair cells gives a hearing loss of approximately 60 decibels (a moderate hearing loss). </p>
<p>So individuals with a loss of outer hair cells are still able to hear, but usually require amplification from hearing aids to perceive softer sounds in speech. </p>
<p>The damage or loss of outer hair cells and/or their stereocilia extends from the base, where high frequencies are located, to the apex, where low frequencies are located, creating a typical sloping hearing loss from high-frequency to low. </p>
<p>This decline starts in the late teen years, so it is for this reason that the Mosquito alarm, designed to emit a very high-pitched noise of 17.4kHz, is so annoying to people in their early twenties and younger.</p><img src="https://counter.theconversation.com/content/14743/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Catherine McMahon receives financial support from the HEARing CRC, established and supported under the Cooperative Research Centres Program – an initiative of the Australian Government. She is affiliated with ARC Centre of Excellence in Cognition and its Disorders (CCD).</span></em></p>You may have read last week that, in a bid to curb graffiti, Sydney’s State Rail may trial Mosquito devices - technology that emits a high-pitched noise that’s audible only to people aged in their early…Catherine McMahon, Head of Audiology, Macquarie UniversityLicensed as Creative Commons – attribution, no derivatives.