Anechoic Chamber

An anechoic chamber is a specially designed room whose walls, ceiling, and floor are lined with deep wedge-shaped absorbers to eliminate virtually all sound reflections at frequencies above a design cutoff (typically 50–100 Hz). The result approximates a free-field condition where only the direct sound from a source reaches the receiver. Anechoic chambers are used for loudspeaker testing, microphone calibration, hearing research, sound power measurements (per ISO 3745), antenna testing, and recording anechoic audio sources for auralization. The absorption wedges are typically 0.5–1.5 m long, made from mineral wool or glass fiber, achieving absorption coefficients above 0.99 at the design frequency and above. Building an anechoic chamber requires massive structural isolation to prevent external noise intrusion. The experience of standing in a full anechoic chamber is disorienting because the complete absence of reflections removes all spatial orientation cues that humans normally rely upon.