Two astronauts cannot hear each other on the moon. Why?

Name the waves of frequency greater than $20,000 \,Hz$. Give one use of these waves.

If the frequency of a tuning fork is $400 \, Hz$ and the speed of sound in air is $340 \, m s^{-1}$,find how far sound travels when the tuning fork makes $16$ vibrations. (in $, m$)

$(a)$ Why does the stage of an auditorium have a curved background,curtains,carpets,and a false ceiling?
$(b)$ The sound of a ringing bell inside a vacuum chamber cannot be heard. Why?

$(a)$ What is reverberation? Write two ways of reducing reverberation.
$(b)$ Distinguish between tone and note.
$(c)$ With the help of a simple diagram,explain how defects in a metal block can be detected using ultrasound.

How do the frequency and amplitudes affect a musical sound?