Reverberation chambers

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��ɫ��Ƶ the reverberation chambers

A reverberation room is designed so that the walls, floor and ceiling reflect almost all the sound back into the room. It is the opposite of an anechoic chamber and is used for different types of acoustical testing. We have both a large and a small chamber. These can be used individually or combined to form a transmission suite.

When a machine or other noise source is placed inside a reverberation chamber, the sound is reflected many times. This produces a non-directional or ‘diffuse’ sound field. We can then calculate the sound power emitted from the machine by measuring the sound level in the chamber. We also take into account the characteristics of the room such as its volume, surface area and reverberation time.

Unlike the sound pressure level produced by a machine or piece of equipment, the sound power level is a property of the machine and is independent of the test environment.

We use our reverberation rooms to measure the sound absorption of:

acoustic materials
wall panels or screens
acoustic tiles
hanging baffles
items of furniture for example theatre seats or office desks and chairs

We can also generate high-intensity diffuse noise fields for acoustic fatigue testing. For example, we test spacecraft and aircraft components. These components must be able to withstand high levels of noise without noise-induced vibration. This can cause wiring or circuit boards to fail.

Part of:

Technical specification

Large reverberation chamber

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built as a single-skin concrete box
isolated from the surrounding building and adjacent test chambers
reinforced concrete walls 305mm thick
internal surfaces finished with a hard gloss paint to give a high sound reflection coefficient

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non-parallel walls with edge lengths 9.15 metres wide, by 6.25 metres long and 6.10 metres high
volume: 348 cubic metres
surface area: 302 square metres

The non-parallel walls and sloping ceiling prevent ‘flutter echoes’ and standing waves, to give a uniform diffuse field within the chamber. 

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heavy double doors 1.98 metres wide by 2.42 metres high
interconnecting doorway or test aperture between the large and small chambers 2.02 metres wide by 2.42 metres high

Sound sources

electropneumatic sound source, driven by compressed air
allows noise levels up to 145dB to be generated for high-intensity noise tests

Small reverberation chamber

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The construction is similar to the large chamber.

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non-parallel walls with edge lengths 6.40 metres  wide, by 4.60 metres long and 4.30 metres high
volume: 131 cubic metres
surface area: 153 square metres

The non-parallel walls and sloping ceiling prevent ‘flutter echoes’ and standing waves, to give a uniform diffuse field within the chamber. 

Sound sources 

The electropneumatic sound source can be used to generate noise levels up to 160dB.

For lower sound levels we use specialist heavy-duty mid- and high-range loudspeakers and subwoofers.

Transmission suite 

Both chambers can be used together as a transmission suite. We can measure transmission losses (noise reduction) of:

walls
partitions
panels
double- or triple-glazing samples

The wall or other test structure is built within the aperture between the 2 chambers and can be up to 2.0 metres wide by 2.4 metres high.  Noise is then generated and measured in one chamber, and the noise transmitted though the test sample is measured in the other chamber.

The drop in sound levels across the test sample enables the transmission loss to be measured in different frequency bands. Similarly the large anechoic and small reverberant chambers can be used where diffuse-field to free-field testing is required.

Control room 

There is a control room serving the 2 chambers. Cable ports give access to and from the chambers.