Reverberation room
Encyclopedia
A reverberation
chamber or room is a room designed to create a diffuse 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 diffuse 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 - additional acoustic diffusers are often used to create more reflecting surfaces and further encourage even distribution of any particular sound field.
The main uses for a reverberation chamber are measurement microphone calibration
, measurement of the sound power of a source, and measurement of the absorption coefficient 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
or pink noise
) so that the resulting sound field contains acoustic energy across the whole audible range.
Reverberation
Reverberation is the persistence of sound in a particular space after the original sound is removed. A reverberation, or reverb, is created when a sound is produced in an enclosed space causing a large number of echoes to build up and then slowly decay as the sound is absorbed by the walls and air...
chamber or room is a room designed to create a diffuse 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 diffuse with increased path length) and have very hard exposed surfaces. The change of impedance
Acoustic impedance
The acoustic impedance at a particular frequency indicates how much sound pressure is generated by a given air vibration at that frequency. The acoustic impedance Z is frequency dependent and is very useful, for example, for describing the behaviour of musical wind instruments...
(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 - additional acoustic diffusers are often used to create more reflecting surfaces and further encourage even distribution of any particular sound field.
The main uses for a reverberation chamber are measurement microphone calibration
Measurement microphone calibration
In order to take a scientific measurement with a microphone, its precise sensitivity must be known . Since this may change over the lifetime of the device, it is necessary to regularly calibrate measurement microphones. This service is offered by some microphone manufacturers and by independent...
, measurement of the sound power of a source, and measurement of the absorption coefficient 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
White noise
White noise is a random signal with a flat power spectral density. In other words, the signal contains equal power within a fixed bandwidth at any center frequency...
or pink noise
Pink noise
Pink noise or 1/ƒ noise is a signal or process with a frequency spectrum such that the power spectral density is inversely proportional to the frequency. In pink noise, each octave carries an equal amount of noise power...
) so that the resulting sound field contains acoustic energy across the whole audible range.
See also
- ReverberationReverberationReverberation is the persistence of sound in a particular space after the original sound is removed. A reverberation, or reverb, is created when a sound is produced in an enclosed space causing a large number of echoes to build up and then slowly decay as the sound is absorbed by the walls and air...
- Echo chamberEcho chamberthumb|right|Echo chamber of the Dresden University of Technologythumb|right|Hamilton Mausoleum has a spectacularly long lasting unplanned echoAn echo chamber is a hollow enclosure used to produce echoing sounds, usually for recording purposes...
: a reverberation room used for music recording - Electromagnetic Reverberation ChamberElectromagnetic Reverberation ChamberAn electromagnetic reverberation chamber is an environment for electromagnetic compatibility testing and other electromagnetic investigations. Electromagnetic reverberation chambers have been introduced first by H.A. Mendes in 1968...
: an electromagneticElectromagnetismElectromagnetism is one of the four fundamental interactions in nature. The other three are the strong interaction, the weak interaction and gravitation...
environment mainly for Electromagnetic CompatibilityElectromagnetic compatibilityElectromagnetic compatibility is the branch of electrical sciences which studies the unintentional generation, propagation and reception of electromagnetic energy with reference to the unwanted effects that such energy may induce...
testing - Anechoic ChamberAnechoic chamberAn anechoic chamber is a room designed to stop reflections of either sound or electromagnetic waves.They are also insulated from exterior sources of noise...
: another acoustic test facility