AMPLITUDE
[Film Technology]
[Film Technology]
Sound wave signal
level, corresponding to the
subjective measure of loudness. Peak value of a
repetitive wave form. The amplitude of a sound wave is the degree of motion of air molecules
within the wave, which corresponds to the extent of rarefaction and compression
that accompanies the wave. The greater the amplitude of the wave, the harder the molecules strike the ear
drum and the louder the sound that is perceived. The amplitude of a sound wave can be expressed in terms of absolute units
by measuring the actual distance of displacement of the air molecules, or the
pressure differential in the compression and rarefaction, or the energy involved.
Ordinary speech, for example, produces sound energy at the rate of about one hundred-thousandth
of a watt. All of these measurements are
extremely difficult to make, however, and the intensity of sounds is generally
expressed by comparing them to a standard sound, measured in decibels.
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