Geophysicists use sound waves to build a picture of the magma and rock beneath this active volcano, most of which is underwater. It’s like CT scanning the Earth.
Do you think you could make an echo at Echo Point in Katoomba?
Flickr/Amanda Slater
When a sound is made, it spreads. And when it hits a hard surface that is far away, it bounces back and comes back to where the sound was made. That’s what we call an echo.
From Long Range Acoustic Devices used to disperse protesters to ear-splitting military drones to songs blasted on rotation to prisoners, ours is an age in which sound has been repositioned as a tool of terror.
The author began hearing the sound at night, between the hours of 10 and 11 p.m.
'Street' via www.shutterstock.com
Shortly after Glen MacPherson started hearing strange humming noises, he created the World Hum and Database Project so people around the world could document their own experiences with the Hum.
Going faster than the speed of sound can create some exciting effects – and it’s not just aircraft that do it.
Urban noise pushes birds to sing in high pitch and ship sound deafens whales and dolphins.
John Haslam, Eric Bégin, IK's World Trip, Green Fire Productions, flickker photos, Jay Ebberly / Flickr