something that goes back and forth.
allows the comparison of "higher" and "lower".
measures its change over a single period.
number of occurrences of a repeating event per unit time.
a movement back and forth in a regular rhythm.
propagated in an elastic medium such as air.
describing the strength of the ear's perception (ability to hear or be aware of something) of a sound.
a measurement of sound in the air at a listener's location.
hearing the least possible amount.
a loud, sudden and short sound.
speaking in a quite or gentle way.