Just when you thought it was safe to have a nap on a train, the window you’re resting your head on might try to sell you a new app, skin cream or tickets to the theatre. Sky Deutschland has announced a new way to deliver advertising to unsuspecting commuters. When you rest your head on the window of the train, a device exploits hearing through bone conduction to send audio messages straight to your inner ear.
The concept has been around for some time, although this appears to be the first time that bone conduction technology has been used in advertising. It has long been a feature of hearing aids and in recent years has been applied to military communication devices, audio headphones and, most recently, Google Glass.
The science behind the technology
We all learned in school that we hear by sound vibrations reaching our inner ear, which are then converted into electrical signals by the cochlea and sent to our brain. The sounds reach our inner ear by travelling down the ear canal, causing vibration of our eardrum and bones in the middle ear (one of which is the smallest bone in the body). This is called hearing by air conduction. What we didn’t learn in school is that we also hear by bone conduction: sounds can reach your inner ear through vibrations of the skull, largely bypassing the ear canal, eardrum and middle ear.
Ever wondered why your recorded voice sounds so different to what you think you sound like? This is because when you talk you hear yourself by both air and bone conduction. When you playback a recording of yourself, you only hear it by air conduction. Bone conduction technology (headphones, some hearing aids and now possibly windows) exploit this mechanism of hearing by sending vibrations through your skull bone directly to your inner ear.
Hearing through your eyeballs
Bone conduction hearing is a collective term for several mechanisms involved in the transmission of vibrations through the body to the inner ear.
One team of researchers has demonstrated that we can hear even when sound is transmitted through the eyeball. This seems to work because the eyeball and inner ear are connected through the plumbing within your head. Beethoven famously composed some of his most important pieces of music when he was deaf. Apparently, he would bite on a rod connected to his piano in order to use bone conduction to overcome his deafness. Two hundred years later, hearing via the teeth is being exploited in a new hearing aid, called the SoundBite.
Some animals are even thought to use bone conduction. Elephants hear vibrations of the earth’s surface, picked up by their feet and transmitted to their ears by bone conduction, for communication. Snakes and the golden mole do something similar to detect predators and prey.
Hard to avoid?
BBDO Germany, the company developing the use of bone conduction in advertising, believes it has promising responses from commuters testing the concept. But does the idea have any mileage?
If you don’t want the peace of your commute disturbed by adverts being channelled directly into your ear, is there an alternative to taking a sledgehammer to the window? You may think that blocking your ears is the solution but you’d be mistaken. This will actually make the adverts louder due to something called the occlusion effect.
Luckily, putting a soft material between you and the window would be more effective, so you might want to start taking a cushion with you when you leave for work in the morning.
This new way of advertising may not have been met enthusiasm by all commuters, and it’s easy to see why. But the technology could have other applications designed to help commuters.
For example, many of us fall asleep on trains and buses, completely oblivious that our stop has come and gone. Announcements through train and bus windows via bone conduction might help us wake up in time. Perhaps we could text our name and destination to the window to get a personalised message, which we’re more likely to respond to in time.
Commuters might warm to the idea of a “talking window” if it helps them get home rather than ending up asleep at the end of the line. Will “talking windows” become a reality in the UK soon? BBDO Germany told the BBC, “At present, this is limited to the German market. If we look into the future everything is possible.” This may be a blessing.