Explain giving scientific reasons. 

The intensity of reverberation is higher in a closed and empty house.

 What is an echo? What factors are important to get a distinct echo?

Where and why are sound absorbing materials used?

The speed of sound in air at $0 °\mathrm{C}$ is $332 \mathrm{m}/\mathrm{s}$. If it increases at the rate of  $0.6 \mathrm{m}/\mathrm{s}$ per degree, what will be the temperature when the velocity has increased to $344 \mathrm{m}/\mathrm{s}$?

Nita heard the sound of lightning after $4$ seconds of seeing it. What was the distance of the lightning from her?

Sunil is standing between two walls. The wall closest to him is at a distance of $360 \mathrm{m}$. If he shouts, he hears the first echo after $\text{4 s}$ and another after another $2$ seconds.

What is the velocity of sound in air?

What is the distance between the two walls?