Reverberation


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Related to Reverberation: Reverberation time, Reflection of sound

Reverberation

After sound has been produced in, or enters, an enclosed space, it is reflected repeatedly by the boundaries of the enclosure, even after the source ceases to emit sound. This prolongation of sound after the original source has stopped is called reverberation. A certain amount of reverberation adds a pleasing characteristic to the acoustical qualities of a room. However, excessive reverberation can ruin the acoustical properties of an otherwise well-designed room. A typical record representing the sound-pressure level at a given point in a room plotted against time, after a sound source has been turned off, is given in the decay curve shown in the illustration. The rate of sound decay is not uniform but fluctuates about an average slope. See Sound

Typical decay curve illustrating reverberationenlarge picture
Typical decay curve illustrating reverberation
McGraw-Hill Concise Encyclopedia of Physics. © 2002 by The McGraw-Hill Companies, Inc.

Reverberation

The buildup of sound within an architectural space, such as a room, as a result of repeated sound reflections at the surfaces of the room.
Illustrated Dictionary of Architecture Copyright © 2012, 2002, 1998 by The McGraw-Hill Companies, Inc. All rights reserved
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Reverberation

 

the process by which a sound in an enclosed space gradually decays after its source ceases to emit. The volume of air in the enclosure constitutes an oscillatory system with many natural frequencies. Each natural oscillation is characterized by a decay rate; the absorption of a sound during its reflection from the boundaries of an enclosure and during its propagation determine the decay rate of the sound. Consequently, the natural oscillations of various frequencies that are excited by the same source do not decay simultaneously.

Reverberation has an important effect on the audibility of speech and music in an enclosure because the listener perceives direct sound against a background of oscillations that have been previously excited in the volume of air; the spectra of these oscillations vary in time because of the gradual decay of the natural oscillations. Reverberation is all the more important when oscillations decay slowly. When the dimensions of a room are large compared with the wavelengths, the spectrum of natural oscillations can be regarded as continuous and reverberation can be represented as the result of both a direct sound and a series of delayed repetitions with decreasing amplitudes, which reflect from the boundary surfaces.

The duration of reverberation is characterized by reverberation time, during which the intensity of a sound decreases by a factor of 106 and the level decreases by 60 decibels. Reverberation time is a very important factor in determining the acoustics of a room. Reverberation time is longer when a room is larger, the time of a free sound path is longer, and there is less absorption by the boundary surfaces. Reverberation time is measured by recording a sound level as it decreases after the source of the sound has been cut off; the recording devices used for this purpose have a logarithmic scale. Reverberation time is calculated from the average slope of the recorded level graph.

Reverberation is also applied to the echoes produced in the ocean by the reflection and scattering of an original sound from the bottom (bottom reverberation), from the agitated surface (surface reverberation), or from a heterogeneous aqueous medium, fish, and other biological objects (volume reverberation).

REFERENCES

Beranek, L. Akuslicheskie izmereniia. Moscow, 1952. (Translated from English.)
Furduev, V. V. Akusticheskie osnovy veshchaniia. Moscow, 1960.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

reverberation

[ri‚vər·bə′rā·shən]
(acoustics)
The prolongation of sound at a given point after direct reception from the source has ceased, due to such causes as reflections from bounding surfaces, scattering from inhomogeneities in a medium, and vibrations excited by the original sound.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

reverberation

The persistence of sound in an enclosed space (such as a room or auditorium) after a source of sound has stopped.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.
References in periodicals archive ?
Reverberation time RT is defined as the time for the sound to decay to a level 60 dB below its original level.
Mittra, "Performance evaluation of a mode-stirred reverberation chamber using the finite difference time domain (FDTD) simulation," in Proceedings of the Asia-Pacific Symposium on Electromagnetic Compatibility, pp.
According to the distance and acoustic intensity reverberation (DAIR) physical model of sound propagation in closed space, the sound pressure level at r from the sound source can be expressed as follows [17]:
Reverberation, as one of the basic physical phenomena in underwater acoustics, the study of it has a long history, and the reverberation theory is becoming mature.
Not only is the reverberation time itself frequency dependent, every signal emitted into the room has its own frequency balance.
For this research project, I used a JND value of 5% (51) for T30 when values were larger than 0.6s, and assumed a fixed value of 0.03s for reverberation times shorter than 0.6s.
We work out a method for evaluating the number of independent positions based on the statistical analysis of multiple fluctuating variables, namely multivariate analysis, collected inside the WV of a reverberation chamber.
Goodness-of-fit (GOF) tests [14] were popularly used in studying the distribution of the random field in a reverberation chamber (RC) [5,6].
"Similar to ATI's horizontally-oriented acoustical reverberation chambers, efficiency of sample installation and testing has been engineered to maximise the testing experience at our facility," stated Eric Miller, director -- acoustics.
A company spokesman said: "Mugen means limitless and Mugenkyo means limitless reverberation, expressing our belief that taiko has no limitations, no musical or geographical boundaries.
Writing for engineers, technicians, and beginning students and using a conventional physical approach, they cover the position of the reverberation chambers in common electromagnetic tests, the main physical features of electromagnetic cavities, the statistical behavior or stirred waves in an oversized cavity, the impact of the physical and technological parameters of a reverberation chamber, radiated immunity tests in a reverberation chamber, emissivity texts, measuring the shielding effectiveness, and a mode stirring reverberation chamber as a research tool.
A school's needs vary as widely as its classroom designs - the ability to hear well with minimal reverberation is paramount in a standard classroom, but in a library or media center, the same speech intelligibility could distract students from reading or studying.