- noun a completely quiet room in which sound or radio waves do not reflect off the walls
- A room whose walls, ceiling, and floor are lined with sound-absorbing materials which minimize or eliminate all sound reflections. Used, for example, to test microphones or sound-level meters. Also called dead room, free field room, or echoless room.
- A room whose walls, ceiling, and floor are lined with materials that absorb radio waves of given frequencies or bands. Used, for example, to test microwave devices.
- synonymanechoic room
- An enclosure whose interior surfaces do not reflect sound.