Reverberation
Hello dear students, in this article we are going to deal with impact of multiple reflection of sound from different surfaces. You must have observed that the auditorium halls always having roofs at higher altitudes. In cinema hall, loud speakers are fitted on the chairs; curtains are used to cover walls. What is the reason behind this? Answer is reverberation. We know that sound waves reflected back from the surface on which is strikes with obeying law of reflection, i.e. angle of incidence is always equal to angle of reflection (∠i=∠r). Due to this sound reflects multiple times from the surrounding objects which cause the persistent of sound. Observe the diagram below,
Here the sound emitted from the source gets reflected multiple times from the walls, roof and other surfaces and then reaches to the ears of listener. This multiple reflection of sound creates the persistence of sound known as reverberation of sound. Reverberation is nothing the echo but the only difference is that for echo the distance between source and listener should be greater than 17 m, whereas reverberation can takes place at any small distances too.
Reverberation can have some advantages as well as some disadvantages too! Let’s discuss them as below,
Disadvantages:
- In auditorium hall, listener receives the sound even though it is stopped, which is not expected.
- Continuous persistent of sound creates strain on listeners’ ear, which can cause headache, deafness etc.
Advantages:
- Reverberation is used in sound recording techniques.
- Stethoscope also uses the phenomenon of reverberation.
Methods to reduce reverberation:
- The walls of big halls like auditorium should be made concave.
- While constructing the walls for the cinema hall, theatre sound absorbing material should be used or the walls should the designed for absorption of sound.
- Walls and floors should be covered with curtains, carpets etc.