Q4 of 12 Page 137

Where and why are sound absorbing materials used?

Sound absorbing materials are used in buildings and offices to prevent transmission or reflection of sound. They prevent leakage of sound to other rooms. Sound absorbing materials also prevent echoes.


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2

Explain giving scientific reasons.

A. The roof of a movie theatre and a conference hall is curved.


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


C. We cannot hear the echo produced in a classroom

 3

Answer the following questions in your own words.

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


B. Study the construction of the Golghumat at Vijapur and discuss the reasons for the multiple echoes produced there.


C. What should be the dimensions and the shape of classrooms so that no echo can be produced there?

 5

Solve the following examples.

The speed of sound in air at 00C is 332 m/s. If it increases at the rate of 0.6 m/s per degree, what will be the temperature when the velocity has increased to 344 m/s?

 5

Solve the following examples.

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