Question

The persistence of sound in a closed enclosure, due to continuous reflections at the walls, even after the source has stopped producing sound is known as
A.The persistence of hearing
B.An echo
C.Reverberation
D.The ultrasounds

Answer 1

First, we have to consider all the acoustic phenomena given in the options. Here, in the case of reverberation, the sound exists even after the source of the original sound has stopped production as a consequence of numerous reflections from surfaces. Now, we can get the answer.

Complete step by step answer: To get the answer to this question, at first, we must know what the term given in the options actually mean.
Persistence of hearing – The time for which the perception of hearing of any kind of sound persists in the brain is known as persistence of hearing. For a normal human ear, the standard value of persistence of hearing is $0.1s$ . Any increase or decrease in the persistence of hearing compared to a normal ear indicates the hearing loss of that ear.
Echo – In acoustics, when a sound wave is reflected from a large object and returns to the listener with a delay after the actual sound, this is known as an echo. The distance between the listener and the reflecting object must be $17.2metre$ to hear echo properly.
Reverberation –
In acoustics, when a sound is created, the persistence of that sound is called reverberation. When a sound wave is reflected to produce a number of reflections that decay gradually as they are absorbed by the surface of any kind of object in space, this phenomenon is known as reverberation.
Ultrasounds –
According to the American National Standards Institute, ultrasound is the sound wave having frequencies greater than $20KHz$ , i.e., the upper limit of frequency, which is audible to a normal human ear.
Now, we can see that the appropriate answer to the given question must be reverberation, which is the prolongation of sound in a closed enclosure due to continuous reflections at the walls, even after the source has stopped producing sound.
Therefore, the correct option is (C) Reverberation.

Note:
When in a hall with sound-reflective surfaces, an individual talks, or sings, or plays any musical instrument, reverberation occurs naturally. Reverberation is also found in various outdoor areas, wherever reflection exists.