Noise, Canceled

摘要

The jet engine growls to life. The seat beneath you vibrates. But all you hear are the dulcet tones of a Bach cantata. Thank you, noise-canceling headphones. And thank you, Fourier transform. This miracle of calm was brought to you by the same equation that can compress image files and predict the tides and motion of the planets. It all comes down to waves. Sound is created by changes in air pressure, rising and falling like swells in the ocean. The faster a sound wave oscillates-that is, the greater its frequency-the higher the sound's pitch. The taller the wave is (its amplitude), the louder the sound. That