$A$ bomb explodes on the Moon. How long will the sound of the explosion take to reach the Earth?

Define the following characteristics of sound:
$(a)$
$(i)$ Pitch
$(ii)$ Loudness
$(iii)$ Quality or Timbre
$(b)$ $A$ boy receives his echo $3 \, s$ later. Find the distance of the reflecting surface from the boy. Speed of sound in air is $342 \, m s^{-1}$.

Which of the following sound waves can we hear? $10 \, Hz, 500 \, Hz, 1500 \, Hz, 12000 \, Hz, 25000 \, Hz$

An echo is heard after $0.8 \, s$,when a person fires a cracker $132.8 \, m$ from a high building. Calculate the speed of sound.

What change,if any,would you expect in the characteristics of musical sound when we increase $(i)$ its frequency and (ii) its amplitude?

$A$ sound wave with frequency higher than $20 \,kHz$ is not audible for human ear. Answer the following in respect of this statement:
$(i)$ What is the term used for such a sound?
$(ii)$ Name two organisms producing sound in this range.
$(iii)$ Write an application of such a wave.