Acoustics

An anechoic chamber is a room in which the walls, floor and ceiling are lined with sound absorbing material, usually foam or glass-fibre wedges.

The lining prevents the reflection of sound from the room boundaries so that 'free-field' conditions exist. The room sounds very 'dead'. Sound measurements are not influenced by the room surfaces, and an anechoic room is an ideal environment for many standard tests such as the measurement of the sound power of a machine, or measurements of microphone and loudspeaker frequency responses.

The Large Anechoic Room at ISVR is one of the largest in the country. It was extensively refurbished during 1995/96 and the original polyurethane foam wedges were replaced with glass fibre wedges.

Built as a box within a box, the room is acoustically isolated from the rest of the building and adjacent chambers by an air gap all around and is supported on vibration isolation mounts. The reinforced concrete walls are 305 mm thick.

There are over 8,000 non-flammable glass-fibre cored wedges, extending 910 mm from the walls, floor and ceiling. Free-field conditions exist at frequencies above 80 Hz.

Without wedges the bare chamber is 9.15 m x 9.15 m x 7.32 m, volume 611 cubic metres. The usable space between the wedges is 7.33 m x 7.33 m x 5.50 m, giving a usable volume of 295 cubic metres.

Outreach visits

To arrange a visit to the anechoic chamber at ISVR contact the Outreach team.

Commercial use

The ISVR test chambers are operated by ISVR Consulting, and are well used not only for University research projects, but also for commercial testing and consultancy. For commercial use, contact ISVR Consulting (www.isvr.co.uk). The ISVR Consulting website includes further details of the test chambers (www.isvr.co.uk/facility.htm) and the laboratory services available (www.isvr.co.uk/labtests/labindex.htm).

ISVR Consulting has produced a brief guide to the ISVR Rayleigh Laboratory test facilities. It gives a description of these facilities, including the Large Anechoic Chamber, with photographs showing access routes and dimensions. The guide is intended to assist clients wishing to test large pieces of equipment. You can download and print the latest version here: www.isvr.co.uk/faciliti/usersguide.pdf.