Answer the follow

A. Echo: An echo is the repetition of original sound because of reflection by a surface.

Factors important to get a distinct echo:

The velocity of sound at 22⁰C temperature is 344 m/s. Our brain retains a sound for 0.1 sec. So to hear a distinct echo, the time taken by the starting sound to get reflected should be greater than 0.1 sec. So the distance between the listener and the reflecting surface at this temperature should be

d = v × t

= 344 m/s × 0.1 s

= 34.4 m.

This is the distance required by the starting sound to reach the reflecting surface, get reflected and reach the listener. So, the distance between the listener and reflecting surface should be atleast half of the above calculated distance i.e. 17.2km.

B. In GolGumbaz and Vijaypur the reason for multiple echoes produced is due to multiple reflections of sound by the tomb. The sound produced gets reflected several times throughout the tomb which is responsible for echos.

C. A classroom should be rectangular in shape and its dimensions should be less than 17.2m for an echo to be not produced at normal room temperature.

Sound absorbing material like should be also used for soundproofing the room.