The loudness of a sound depends upon

The walls of a hall built for musical concert should

An echo is returned in $6$ seconds. What is the distance of the reflecting surface from the source (in $, m$)? [Given that the speed of sound is $342 \, m s^{-1}$]

What is a wave?

State whether the following statement is true or false: Sound and light travel in a medium in the form of crests and troughs and rarefactions and compressions respectively.

How does the sound produced by a musical instrument reach your ears? Astronauts need radio transmitters to talk to each other on the moon. Why?