Why Do Sounds Vary From Low to High Pitch?

Sound varies from low to high pitch in direct relation to the frequency of the sound wave. Sound waves oscillate, and the number of times per second a sound wave oscillates is known as its frequency. A higher frequency produces a higher pitch, while a lower frequency results in a lower pitch.

Sound waves are analogous to the ripples created on a pond from a tossed stone; the distance between the ripples is representative of the frequency, or the pitch, of the sound wave. More ripples moving past a given area over the course of one second would be commensurate with a higher pitch, while fewer ripples would indicate a lower tone.

Another example of the frequency and pitch relationship is the Doppler effect. This phenomenon occurs when a sound source, or the listener, is in motion and also occurs when both are moving, according to About.com. As a moving sound source moves toward a listener, or the reverse, the leading sound waves are slightly closer together, and when the source or listener passes, the trailing sound waves spread farther apart. This is observed when a train or ambulance passes a particular location, as the sound produces a steadily higher pitch as it approaches, then a progressively lower pitch as it moves away.