Literally meaning "without echo". A room whose boundaries effectively absorb all incident sound over the frequency range of interest, thereby creating essentially free field conditions. This allows measurements to be made without them being contaminated with reflected waves from the walls, ceiling and floor.
Rooms of this type are used to test audio equipment such as loudspeakers and microphones and for other types of research.
A secondary wire mesh floor in the middle of the room is often used When larger objects need to be accomodated.
ISO 3745:1983, Acoustics - Determination of sound power levels of noise sources - Precision methods for anechoic and semi-anechoic rooms.
Subjects: Noise & Vibration