Question

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? 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

The loudness of the sound increases gradually as the air is slowly introduced in to the jar. This is because sound needs a physical medium and in a vacuum there is none. The air provides that medium and as it is introduced, the transfer of sound energy increases