Semi-Anechoic Room

The Semi-Anechoic Room where sound reflections only come from the floor. The walls and ceiling are absorbent making it ideal for acoustic testing.

The solid floor makes this room much easier to work in than the anechoic chamber, because equipment can be stood on the solid floor. Often, we put absorbent material on the floor to reduce floor reflections.

Example application – diffuser scattering

The standard method for testing room acoustic diffusion coefficients was developed as part of a research project at Salford. The most efficient method is done in a semi-anechoic chamber with all the microphones, the loudspeaker and diffuser sample placed on the hard floor in a boundary plane measurement. The absorbent walls and ceiling then prevent unwanted reflections. The semi-anechoic room is quiet so background noise doesn’t affect measurement accuracy.

Example application – public engagement

Television has always enjoyed filming in our anechoic chambers. Our first chamber was used as a mock up of a torture chamber for Granada TV, and more recently, Richard Hammond was filmed by National Geographic breaking a glass using the sound from his guitar. Producers like the anechoic chamber, but often use the semi-anechoic because of problems setting up equipment on a trampoline floor. We filmed high speed footage of acoustic phenomena in this room, and have used it to make videos for use in classrooms.

Vital statistics

Background noise level 3.8dBA
Working volume 4.2m × 3.3m × 3.0m
Cut-off frequency 250Hz

Tests and standards

Sound power level measurement to BS ISO 3744 / ISO 3745 and BS 4196