Why does the sound produced by a tuning fork become louder when the stem of the fork is pressed on the top of a table?

Why does the sound produced by a tuning fork become louder when the stem of the fork is pressed on the top of a table?
Ans: This phenomenon is based on the surface area of the vibrating substances. One of the factors on which the loudness of sound depends on is the surface area of the area available for vibration. When only the tuning fork is used, it causes vibration of air of a very small area, which makes it appear feeble. But when its stem is pressed against a tabletop, the whole of the top vibrates, which causes the vibration of a large area of air. This makes it appear loud.