When a tuning fork [vibrating] is held close to ear

When a tuning fork [vibrating] is held close to ear, one hears a faint hum. The same [vibrating tuning fork] is held such that its stem is in contact with the table surface, then one hears a loud sound. Explain.

Answer

A tuning fork held close to ear, disturbs a small volume of air and hence, sound heard is faint. When the handle of the vibrating tuning fork is held against table it sets up forced vibrations in the tabletop. As tabletop has a large surface area large volume of air is set into vibration transmitting more energy thereby producing loud sound.