Sound waves for bats to get around in the dark?

To help them find their prey in the dark, most bat species have developed a remarkable navigation system called echolocation. To understand how echolocation works, imagine an "echo canyon." If you stand on the edge of a canyon and shout "hello," you'll hear your own voice coming back to you an instant later. The process that makes this happen is pretty simple. You produced sound by rushing air from your lungs past your vibrating vocal chords. These vibrations caused fluctuations in the rushing air, which formed a sound wave. A sound wave is just a moving pattern of fluctuations in air pressure. The changing air pressure pushes surrounding air particles out and then pulls them back in. These particles then push and pull the particles next to them, passing on the energy and pattern of the sound. In this way, sound can travel long distances through the air. The pitch and tone of the sound are determined by the frequency of the air-pressure fluctuations, which is determined by the way you move your vocal chords. When you shout, you produce a sound wave that travels across the canyon. The rock face on the opposite side of the canyon deflects the air-pressure energy of the sound wave so that it begins moving in the opposite direction, heading back to you. In an area where atmospheric air pressure and air composition is constant, sound waves always move at the same speed. If you knew the speed of sound in the area, and you had a very precise stopwatch, you could use sound to determine the distance across the canyon.