They are called noises.
When sounds are repeated at regular intervals, what do they become?
They become musical sounds.
Upon what do the high and low sounds in music depend?
They depend upon the rapidity with which the waves are produced in the air.
When the waves are repeated rapidly, what sound is made?
They make a high or acute sound.
When they are repeated more slowly, what sound is made?
They make a low or grave sound.
How small a number of vibrations or waves in the air can be heard?