A specially equipped room for acoustic measurements under conditions approaching those of free open space (in a free sound field). The walls, floor and ceiling of an anechoic chamber are covered with sound-absorbing materials that ensure the practically complete absence of reflected sound waves. In modern anechoic chambers the sound-deadening lining consists of wedges of a light porous material (glass fibre) attached to the walls by their bases. In large anechoic chambers it is possible to obtain the absorption of up to 99% of the energy of a sound wave in the frequency range from 50 — 70 Hz up to the highest audible frequencies.
Anechoic chambers are used for the calibration of measuring microphones, the testing of loudspeakers, studies of the noise of machines, transformers and other objects, the determination of the threshold of hearing and other measurements for the purposes of physiological acoustics.
Anechoic chambers are used for the calibration of measuring microphones, the testing of loudspeakers, studies of the noise of machines, transformers and other objects, the determination of the threshold of hearing and other measurements for the purposes of physiological acoustics.