A source of sound is kept in a jar in a vacuum. Air is slowly introduced in to the jar. What happens to the sound coming out of the jar?

Question

A.
The loudness of the sound increases gradually.
B.
The loudness of the source decreases gradually.
C.
The sound remains unchanged.
D.
The pitch of the sound increases gradually.
E.
The pitch of the sound decreases gradually.

Answer 1

As air is gradually introduced into the jar from a vacuum, the medium through which the sound is transmitted changes. In a vacuum, sound cannot travel because there are no particles to carry the sound waves. When air is introduced, sound can begin to travel through the medium. Initially, as more air is added, you will hear the sound more clearly, and its loudness will increase.

Thus, the most appropriate choice is:

A. The loudness of the sound increases gradually.