The Anechoic Chamber
‘An-echo-ic’ means without echoes. An anechoic chamber is a room in which the walls, floor and ceiling are lined with sound absorbing material, usually polyurethane foam or glass-fibre wedges. The lining prevents the reflection of sound from the room walls, floor or ceiling 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 acoustical tests such as the measurement of the sound power of a machine, or measurements of microphone and loudspeaker frequency responses.
The Large Anechoic Chamber at the ISVR is one of the largest in the country. It was extensively refurbished during the summer of 2022 when new polyurethane wedges were installed, along with a new wire-mesh or ‘trampoline’ floor, and removable load-bearing floor panels.
The Large Anechoic Chamber, together with the adjacent Reverberation Chambers, is part of the University’s Rayleigh Laboratories operated by ISVR Consulting.
Built as a concrete box, it is acoustically isolated from the rest of the building and the adjacent reverberation chambers by an air gap all around. The reinforced concrete walls are 305 mm thick to insulate against external noise.
There are approximately 3209 non-flammable open-cell polyurethane wedges, extending 1.2 metres from the walls, floor and ceiling. Free-field conditions exist at frequencies above 70 Hz.
Without wedges, the bare chamber is 9.15 m × 9.15 m × 7.32 m high, with a volume 611 cubic metres. The usable space between the wedge tips is 6.70 m × 6.70 m (width × depth), and the height from the load bearing floor to the ceiling wedge tips is 4.86 m, giving a usable volume of 218 cubic metres.
Main access is through a heavy laminated door from the corridor, 1.29 m wide × 2.10 m high. This door slides back from the chamber entrance on a guide rail and is pneumatically operated.
Alternative access for larger items is through double doors, 2.0 m wide × 2.4 m high.
A permanent wire-mesh floor can be walked on and will support a distributed load of 8 persons.
A load-bearing floor made up of removable GRP grid panels can be installed above the wire-mesh floor. These panels, supported on removable posts, are 600 mm square. As many or as few panels as required can be installed to support equipment under test or microphone stands. This floor can support a spread load of several tons with a minimum of interference with the anechoic nature of the chamber.
The load-bearing floor is at the same level as the corridor, allowing step-free access.
An optional floor of varnished chipboard can be laid over the load-bearing floor for measurements requiring a ‘free field above a reflecting plane’ (hemi-anechoic conditions), as required by some test standards.
There is a control room adjacent to the Large Anechoic Chamber allowing laptops, instrumentation and equipment to be placed outside the chamber, with cable ports giving access to and from the chamber and the adjacent Reverberation Chambers.
Research and consultancy
The Large Anechoic Chamber is well used, not only for University research projects, but also for commercial testing and consultancy. Typical uses include the measurement of sound power to British, European and International standards, measurements of frequency responses and other properties of microphones, loudspeakers and audio equipment, and measurement of the sound levels and spectra of alarm sounders such as smoke alarms, or more recently, train and fog horns.
A list of the standards we test to is available.
ISVR Consulting is an Enterprise Unit linked to the Institute of Sound and Vibration Research at the University of Southampton. We work with a wide range of industrial and commercial clients, public bodies, and government agencies in the UK and Europe.
ISVR Consulting carries out tests on behalf of clients and has a wide range of specialist acoustical instrumentation and audio test equipment available . Our staff normally conduct the tests, but you can also hire the chamber to carry out your own testing with your own instrumentation, with our expertise on hand should you need it.
ISVR Consulting has produced a downloadable guide to test facilities in pdf format. This gives additional information on cable ports, single- and three-phase electrical supplies, workshop facilities, air supplies, access and dimensions, etc. The guide is intended to assist clients wishing to test large pieces of equipment.
Get in touch to find out more about our facilities and how we might be able to work with you.
Address: ISVR Consulting, Building 15 (M27), University of Southampton, University Road, Southampton, SO17 1BJ.
There are detailed directions to our location on our ‘Contact Us‘ page.