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Model Paper 10 — Science STD 9 — Question

Gujarat BoardEnglish MediumSTD 9ScienceModel Paper 103 Marks
Question
i. What is the difference between echo and reverberation?
ii. How can we reduce reverberation in an auditorium or a big hall?
iii. Which materials are good absorbers of sound?
iv. Why we can hear more clearly in a room having curtains?
✓

Answer

i. The repetition of sound caused by the reflection of sound waves from an obstacle is known as an echo whereas the phenomenon of persistence or prolongation of audible sound after the source has stopped emitting it is called reverberation.
ii. In an auditorium or big hall, excessive reverberation is highly undesirable. To reduce reverberation, the roof and walls of the auditorium are generally covered with sound-absorbent materials like compressed fibreboard, rough plaster or draperies.
iii. The soft and the porous materials are bad reflectors of sound but are good absorbers of sound.
iv. We can hear more clearly in a room having curtains because curtains are bad reflectors of sound. The curtains absorb most of the sound falling on them, and hence do not produce echoes.

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