Question

Why the stringed instruments are provided with hollow boxes?

Answer 1

Musical instruments are provided with a hollow box. eg- guitar.
In the musical instruments ,if the string is set into vibration ,the forced vibrations are produced in the air inside the box. Since area of the hollow box is large ,so it sets a large volume of air into vibration of the same frequency as that of string. Therefore, a loud sound is produced due to resonance. The sound produced by vibrating string is too weak to be heard.