07 Reverberation

  • The persistence of sound as a result of repeated reflections from surfaces such as furniture, people, air etc. within a closed surface, is called reverberation.
  • Reverberation big halls and auditoriums, like:
    • During an assembly inside the school auditorium, the voice of the orator appears different from the original.
    • Also, the sound produced by the musical instruments during a concert in a closed hall appears very different when compared to its original sound.
  • The reflections caused by reverberation, build up with each reflection and decay gradually, as they are absorbed by the surfaces of objects in the space enclosed.


Reverberation is same as the echo, except that the distance between source of sound and also the obstacle through which it gets reflected is lesser in case of this reverberation.


  • Reverberation time is the length of the time where the sound decays by about 60 decibels starting from the initial level.
  • The time delay during reverberation is said to be not less than 0.1 Second. In other words, the reflected wave reaches the observer in more or less than 0.1 Second..
  • In reverberation, the delay in perception of the sound and the original sound is very less. So, the original sound will be still in the memory when this reflected sound is heard.
  • Reverberation time gives the quantitative characterization of the reverberation.


  • In case of excessive reverberations, the sound is said to run together with a mere loss of articulation, and it becomes muddy and also garbled.
  • The sound bounces back between the surfaces if a room has no sound absorbing surfaces like wall, roof and the floor. It takes a very long time for the sound to die.
  • In such a room, the listener is unable to interpret the speaker clearly as he tends to hears both the direct sound as well as the repeated reflected sound waves.


Reverberation enhances the quality of sound. When the right amount of reverberation is present, the sound quality gets enhanced drastically. This in turn, does wonders in musical symphonies and orchestra halls. So, sound engineers are appointed during the construction of these halls.


  • The phenomenon of reverberation is utilized by the producers of live or recorded music in order to enhance the sound quality using several systems to produce and simulate reverberations.
  • A plate reverberator is a device, where a metal plate is used to produce vibrations instead of a loudspeaker.
  • Chamber reverberator is one such example, where sound is produced by a loudspeaker and then picked by a microphone along with other effects of the reverb.


The methods used for reducing excessive reverberation in big halls and auditoriums are as follows:

  • Panels made of sound-absorbing materials (like compressed fibreboard or left) are put on the walls and ceiling of big halls and auditoriums to reduce reverberations.
  • Carpets are put on the floor to absorb sound and reduce reverberations.
  • Heavy curtains are put on doors and windows to absorb sound and reduce reverberations.
  • The material having sound-absorbing properties is used for making the seats. Porous materials such as mineral wool and fiberglass are examples of absorbents. As the sound waves penetrate mineral wool, sound energy gets converted to heat through friction.

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