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Acoustics Testing

Sound absorption


Danny McCaul
t: +44 (0)161 295 4615

What is absorption?

When sound hits a reflective surface it bounces back making the sound reflect around in the room, a good example of a reverberant space with hard surfaces like this is a railway station. When sound hits a soft surface some of the sound energy is lost to the surface, this is absorption. So when we measure  the absorption coefficients of a surface it is a measure of the amount of sound energy lost to the surface. We can measure absorption in our large reverberation room.



What is expected of you?

Written descriptions of the samples must be provided prior to testing including mass per unit area and thickness of the sample (preferably prior to quotation); a test report cannot be provided without this information. If your sample is a simple product such as carpet tiles, an insulating product or  floor covering you can send the sample to us and we will install it for testing when the large reverberation room is available for use. If the sample is of a more complex nature, tiles installed over a cavity or rock wool, for example, we recommend that you carry out the construction on the day of testing.


What do the results look like?

The results will be presented as part of a complete report. A single figure weighted sound absorption coefficient (aW) will be calculated, and the classification provided. The absorption coefficient values (aS) for each 1/3rd octave value will also be calculated. These results will be presented in a  manner accordant with the BS EN ISO 354 standard; a specimen results sheet is available. Please note the results are not pass/fail criterion.

What size of sample should I provide?

A 12m2 sample the ratio of the dimensions is important; a 3m x 4m sample is adequate to fulfil the requirements of the standard.  

What do our customers most often forget when preparing for testing at the laboratory?

If the sample is thin (less than 1cm) you will need to supply cloth tape to seal the edges (unless the sample is carpet tiles). If it is more than 1cm thick you will need to provide a timber border not more than 2cm in width.

How long is each test?

The first test is always the longest because empty room reverberation times need to be measured prior to testing. After calibration the first test should take 40-60mins and subsequent tests should take 30mins.

How many tests can I do in a day?

Provided the installation of the sample doesn’t hold us up too much we should be able to do up to four sound absorption tests in a day. If necessary we can do more than this for an additional charge.

Discounts (multiple tests)

The first test of each day includes calibration and set up of equipment therefore subsequent tests on the same day are cheaper than then first.

When will I get the report? When can I get the results?

We can provide preliminary results on the day of test. The test report will follow in 2-4 weeks after test completion, depending on our workload and the complexity of the test carried out.