Reverberation chamber

A review of the common methods of measuring acoustic absorption and dispersion is presented by Cottrell and McCoubrey [9], The ultrasonic interferometer, the absorption tube, the condenser transducer, and the reverberation chamber are the standard types of apparatus. 

In a free acoustic field such as that in an open air or anechoic chamber, the pressure and intensity levels in the direction of propagation are numerically the same. In a diffuse field in which sound is reflected so many times that it travels in all directions with equal magnitude and probability (reverberation chamber), the pressure and intensity levels are different and this difference is known as the pressure-intensity index (phase index or reactivity index). 

Freyer GJ (2003) Distribution of responses for limited aspeet angle EME tests of equipment with struetured direetional direetivity. Reverberation Chamber, Aneehoie Chamber and OATS Users Meeting, Austin TX, April 2003... 

Anechoic A room that has a low degree of acoustic reverberation, such as an anechoic test chamber. 

N. V. Kantartzis and T. D. Tsiboukis, Unconditionally Stable Numerical Modeling and Broadband Optimization of Arbitrarily-Shaped Anechoic and Reverberating EMC Chambers, in Proc. 6th Europe Int. Symp. Electromagn. Compat., Eindhoven, The Netherlands, Sep. 2004, vol. 1, pp. 48-53. 

What became known as the Leblanc process was actually several interrelated processes. Salt was first reacted with sulphuric acid in a cast-iron pan, then in a reverberator furnace (in which heat was apphed from a flame blown from a separate chamber, not in direct contact with the salt), to produce saltcake (sodium sulphate), with hydrochloric acid released as a waste gas. Saltcake was used to make sodium carbonate, or roasted with limestone (calcium carbonate) and coal or coke to produce black ash. This mixture of sodium carbonate, calcium sulphide, sodium sulphide, hme, salt, carbon, and ash could be treated further with hot water to produce impure sodium carbonate in solution, evaporated into soda crystals (washing soda), or heated to yield anhydrous sodium carbonate. The latter, in turn, could be reacted with lime to made caustic soda (sodium hydroxide), the strongest commercial alkali then available. 

When sound waves come in contact with a boundary obstacle, such as a wall or door, a portion of the sound wave energy is reflected, a portion is transmitted through the obstacle, and the rest is absorbed by the obstacle. One of the standard methods of measuring the effective sound absorption coefficient of an acoustical material is by finding its effect on the reverberation time, or decay rate, of the sound pressure level in the sound chamber. The total sound absorption in the receiving room is required to determine the noise reduction of the specimen being tested. The key here is to rule out the absorption of sound waves within the chamber that may be attributed to the door being tested. 

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