SOUND – ECHO
The repetition of sound caused by the reflection of sound waves is called an echo. An echo is heard when sound is reflected from a hard surface such as a tall brick wall or a cliff. A soft surface tends to absorb sound, so there is no echo. The human ear can hear two sounds separately only if there is a time interval (or time gap) of (1/10)th of a second (or more) between the two sounds.
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SOUND – Reverberation
If a sound is made in a big hall, the sound waves are reflected repeatedly from the walls, ceiling and floor of the hall, and produce many echoes. The echo time is, however, so short that the many echoes overlap with the original sound. Due to this the original sound seems to be prolonged and lasts for a longer time. The persistence of sound in a big hall due to repeated reflections from the walls, ceiling and floor of the hall is called reverberation.
- A short reverberation is desirable in a concert hall (where music is being played) because it gives ‘life’ to sound and boosts the sound level.
- But if the reverberation is too long, then the sound becomes blurred, distorted and confusing due to overlapping of different sounds.
Modern concert halls are designed for the optimum amount of reverberation.
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