Question

Why is the loudness of the sound heard by a plucked wire increased when it is mounted on a sound board?

Answer 1

A plucked wire has a small surface area so the amount of vibration set up in the air by the string is less. This implies that the amplitude of the sound is less, so the loudness is less. But when it is attached to a sound box or a hollow body, it increases the volume of air that can vibrate and hence the loudness increases.