The Acoustics of Gases. The high-pitched version of your voice that you hear when you inhale helium represents a cool principle. Unlike the speed of light, the speed of sound is quite sensitive to the composition of the medium that it travels through. A gas such as helium that is much less dense than the air we normally breathe and hear in will actually cause the speed of sound to increase, a phenomenon that we perceive as a Chipmunks-like change in pitch. A couple of scientists have used this relationship between sound frequency and gas composition to invent an acoustic device for monitoring the gas composition of air. Of course , if you're a canary this is nothing new.
posted on Oct 25, 2005 - View this thread