3.32 relate the loudness of a sound to the amplitude of vibration.

As we know the higher the amplitude, the louder the sound.
If you take a ruler and place it off the edge of the table. If you hold the end of the ruler that's on the table and flick the end that's off the edge a sound will be made. The further you hold the ruler off the table the louder it will be because of the increased amplitude.