A picture of an anechoic chamber

An anechoic chamber is a room that is isolated from external sound or electromagnetic radiation sources, sometimes using sound proofing, and prevents the reflection of wave phenomena (reverberation). Anechoic chambers are widely used for measuring the acoustic properties of acoustic instruments, measuring the transfer functions of electro-acoustic devices, testing microphones and performing psychoacoustics experiments (such as measuring the quality of audio codecs or measuring head-related transfer functions). Photo of an anechoic chamber Photo was taken at the Kyushu Institute of Designs anechoic chamber by Alexis Glass. ... Photo of an anechoic chamber Photo was taken at the Kyushu Institute of Designs anechoic chamber by Alexis Glass. ... A schematic representation of hearing. ... Sound proofing is any mechanism used to reduce the conduction of sound through a barrier or into a soundproofed chamber. ... When sound is produced in an enclosed space multiple reflections build up and blend together creating reverberation or reverb. ... Acoustics is a branch of physics and is the study of sound, mechanical waves in gases, liquids, and solids. ... An instrument is a concrete or abstract tool intended for a purpose other than mechanical work, in particular a refined one. ... A transfer function is a mathematical representation of the relation between the input and output of a linear time-invariant system. ... Inside a condenser microphone. ... Psychoacoustics is the study of subjective human perception of sounds. ... Codec is a portmanteau of either Compressor-Decompressor or Coder-Decoder, which describes a device or program capable of performing transformations on a data stream or signal. ... HRTFs for left and right ear (expressed here as HRIRs) describe the filtering of a sound source (x(t)) before it is perceived at the left and right ears as xL(t) and xR(t), respectively. ...

Anechoic chambers, modeled after the world's first wedge-based anechoic chamber at Murray Hill, Bell Labs, typically use fiberglass wedges on all walls of the chamber to absorb incoming sound waves. The wedge shape acts as a waveguide to focus incoming sound into the fiberglass wedge, where the acoustic energy is converted to heat. The alternating pattern is used to achieve a more uniform angular absorption. Frequencies below 200 Hz are not as effectively absorbed by the wedges. Murray Hill is a locality of Berkeley Heights, New Jersey located in Union County in north-central New Jersey. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Fiberglass or fibreglass is material made from extremely fine fibers of glass. ... In physics, optics, and telecommunication, a waveguide is an inhomogeneous (structured) material medium that confines and guides a propagating electromagnetic wave. ... The hertz (symbol Hz) is the SI unit of frequency. ...

Anechoic chambers in which the bottom is also composed of wedges have the floor formed by a wire cage suspended above the bottom by wires. Other anechoic chambers only use wedges for five of the six sides of the room. To prevent external sounds from entering the anechoic chamber, most are encased in a meter or more of cement and may be surrounded by additional insulating materials.

John Cage, a 20th century composer, cited his experience in Harvard University's anechoic chamber in the 1940s — a room in which he expected to hear nothing, but heard instead what was believed to be the sound of his own bloodflow and nervous system — as the inspiration for his famous "silent" composition, 4' 33". John Cage John Milton Cage (September 5, 1912 – August 12, 1992) was an American experimental music composer and writer. ... (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999 in the... Harvard University is a private university in Cambridge, Massachusetts, USA, and a member of the Ivy League. ... // Events and trends The 1940s were dominated by World War II, the most destructive armed conflict in history. ... The title given to this article is incorrect due to technical limitations. ...

Anechoic chambers for electromagnetic radiation absorption are used in the aerospace industry for radar cross section measurement, among other areas. Klystrons give off both ionizing and electromagnetic radiation. ... Radar cross section (RCS) is a description of how an object reflects an incident electromagnetic wave. ...

External links

• Bell Labs' Murray Hill anechoic chamber