Sound is the vibration of air particles. If the vibration is continuous and regular, then the sound can be described by its frequency, as the number of waves per second, quantified in Hertz (Hz). For the time interval in Figure 22-1, the blue sound wave has two complete cycles, while the red sound wave has four complete cycles, so double the frequency and half the wavelength of the blue sound wave. For electromagnetic and sound waves, wavelength is the speed of light and sound, respectively, divided by the frequency.
Figure 22-1
Two different frequencies
The human ear can hear sounds with frequencies ...
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