$A$ person fires a gun in front of a building $167 \ m$ away. If the speed of sound is $334 \ m \ s^{-1}$,calculate the time in which he hears an echo. (in $s$)

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

If an explosion takes place at the bottom of a lake,what type of shock waves will be produced in the water?

$(a)$ Why are sound waves called mechanical waves? List two practical applications of reflection of these waves.
$(b)$ $A$ stone is dropped from the top of a tower $125 \ m$ high into a pond of water at the base of the tower. When is the splash heard at the top? $(g = 10 \ m s^{-2}$ and speed of sound $= 340 \ m s^{-1})$

$(i)$ Which property of sound wave determines:
$(a)$ loudness
$(b)$ pitch?
$(ii)$ $A$ $SONAR$ station picks up a return signal after $3 \ s$. How far away is the object? (Speed of sound in water is $1440 \ m \ s^{-1}$)
$(iii)$ How can reverberations in a big hall or auditorium be reduced?

State whether the following statement is true or false:
The frequency of a sounding body with a time period of $0.01 \, s$ is $100 \, Hz$.