Reverberation Chamber

a room used for acoustic measurements, in which sound is reflected as completely as possible from enclosing surfaces, the average sound pressure is the same at every point, and the arrival of sound waves from different directions is equally probable.

The walls of a reverberation chamber are built of reinforced concrete and brick, while the interior surface is finished with materials that exhibit minimum sound absorption, such as high-grade cement mortar and marble. A diffusive sound field is achieved by making the reverberation chamber irregular in shape, with nonparallel enclosing surfaces and specially designed irregularities on the walls, and by suspending reflecting elements in the form of curved plates in a random fashion throughout the room. A reverberation chamber is usually insulated from external noise and vibrations. A sound field is produced within the room with two to four loudspeakers oriented toward the corners of the room.

A reverberation chamber with a volume of approximately 200 m³ can be used for measuring the sound absorption factor of various materials, calibrating microphone and noise meters, and measuring the volume of the loudspeakers and the acoustic output of machines and other sources of noise. Hearing tests and noise-level tests are also conducted in reverberation chambers.

Sometimes reverberation chambers are also used to measure the characteristics of electromagnetic waves; in this case, the inside of the room is finished with copper foil. Two adjacent reverberation chambers, each having a volume of approximately 50 m³ and a common aperture in one of the walls, are used to study the sound-isolation properties of various materials and structures in architectural and construction acoustics. The quality of a reverberation chamber is characterized by its reverberation time and the uniformity of its sound field.