What Is Sound Frequency?


Quick Answer

The frequency of a sound is the rate at which wave crests reach a given point. Sound waves propagate outward from their source, as a series of compressions and rarefactions of the surrounding air. The peak of each cycle can be plotted as the crest of a wave, as can the low point or trough. The frequency with which these crests and troughs arrive gives sound its pitch.

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Full Answer

The Physics Classroom explains that the distance between the peak of one sound wave and another is known as the sound's period. A low period corresponds to a short distance between the wave crests, while a long distance between the wave crests corresponds to a long period. The period of a sound is thus the inverse of its frequency.

Low-period tones have a short distance between crests and, therefore, the waves are reaching their observer rapidly and with a high frequency. This raises the pitch of the tone. Low-frequency sound waves are stretched out, with a long period between them, so fewer wave crests reach the observer in a given length of time. Sound frequencies are expressed in units of vibrations per second, or Hertz, where 1 wave crest per second gives a frequency of 1 Hz.

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