A reverberation room or reverberation chamber is a room designed to create
reverberation
In acoustics, reverberation (commonly shortened to reverb) is a persistence of sound after it is produced. It is often created when a sound is reflection (physics), reflected on surfaces, causing multiple reflections that build up and then de ...
, a
diffuse
Diffusion is the net movement of anything (for example, atoms, ions, molecules, energy) generally from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in Gibbs free energy or chemical p ...
or random incidence sound field (i.e. one with a uniform distribution of acoustic energy and random direction of sound incidence over a short time period). Reverberation chambers tend to be large rooms (the resulting sound field becomes more diffused with increased path length) and have very hard exposed surfaces. The change of
impedance (compared to the air) these surfaces present to incident sound is so large that virtually all of the acoustic energy that hits a surface is reflected back into the room. Arranging the room surfaces (including the ceiling) to be non-parallel helps inhibit the formation of
standing waves
In physics, a standing wave, also known as a stationary wave, is a wave that oscillates in time but whose peak amplitude profile does not move in space. The peak amplitude of the wave oscillations at any point in space is constant with respect t ...
- additional acoustic
diffusers are often used to create more reflecting surfaces and further encourage even distribution of any particular sound field.
Reverberation chambers are used in acoustics as well as in electrodynamics, such as for
measurement microphone calibration
In order to take a scientific measurement with a microphone, its precise sensitivity must be known (in volts per pascal). Since this may change over the lifetime of the device, it is necessary to regularly calibrate measurement microphones. Thi ...
, measurement of the
sound power
Sound power or acoustic power is the rate at which sound energy is emitted, reflected, Acoustic transmission, transmitted or received, per unit time. It is defined as "through a surface, the product of the sound pressure, and the component of the ...
of a source, and measurement of the
absorption coefficient
The linear attenuation coefficient, attenuation coefficient, or narrow-beam attenuation coefficient characterizes how easily a volume of material can be penetrated by a beam of light, sound, particles, or other energy or matter. A coefficient val ...
of a material. All these techniques assume the sound field in the chamber to be diffuse, and will normally use a broadband sound source (e.g.
white noise
In signal processing, white noise is a random signal having equal intensity at different frequencies, giving it a constant power spectral density. The term is used with this or similar meanings in many scientific and technical disciplines, i ...
or
pink noise
Pink noise, noise, fractional noise or fractal noise is a signal (information theory), signal or process with a frequency spectrum such that the power spectral density (power per frequency interval) is inversely proportional to the frequenc ...
) so that the resulting sound field contains acoustic energy across the whole audible range.
See also
*
Anechoic chamber
An anechoic chamber (''an-echoic'' meaning "non-reflective" or "without echoes") is a room designed to stop reflection (physics), reflections or Echo (phenomenon), echoes of either sound or electromagnetic waves. They are also often isolate ...
, an acoustic test facility which minimizes reverberation
*
Echo chamber
Echo chamber of the Dresden University of Technology
Hamilton Mausoleum has a long-lasting unplanned echo
An echo chamber is a hollow enclosure used to produce reverberation, usually for recording purposes. A traditional echo chamber is cove ...
, a reverberation room used for music recording
*
Electromagnetic reverberation chamber, an
electromagnetic
In physics, electromagnetism is an interaction that occurs between particles with electric charge via electromagnetic fields. The electromagnetic force is one of the four fundamental forces of nature. It is the dominant force in the interacti ...
environment mainly for
electromagnetic compatibility testing
References
ISO Standard for Measurement of Acoustic Absorption in a Reverberation Room
External links
360 video of a reverberation chamberPictures and further description of a reverberation chamber
Acoustics
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