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Sound insulation testing is the process for measuring the amount of noise that passes through a partition, which is usually a floor or a wall for building regulations testing purposes but could be a product such as a window or a door when testing using a sound insulation suite in a laboratory.
By understanding the sound insulation between two rooms separated by the partition, we find out how much noise is stopped by the partition in 16 different frequency bands and report them back to the end user as a single frequency result.
Sound insulation is measured in two ways, depending on whether the test is an airborne sound insulation test or an impact sound insulation test. Where homes and apartments are only adjoined side by side, we conduct only airborne sound insulation testing. Where the homes are above and below one another, we conduct both airborne and impact sound insulation tests.
We always test from a ‘source room’ to a ‘receive room’.
We measure airborne sound insulation using a large speaker which is programmed to generate around 100dB of white or pink noise. What noise sounds very much like an untuned television or radio (before they became digital!). Pink noise is very similar, but a level of control is placed on the noise to ensure frequency bands output a similar amount of energy.
We place a speaker into the source room, turn it up to 100dB (or louder, if we can) and measure the noise output in the source room from that speaker. It can get very loud so ear protection is a must. We call this measure L1 (L stands for Level, so it’s the Level in room 1). We then leave the speaker where it is, move to the receive room and measure the amount of noise in the receive room. We call this measurement L2. In theory we already have our sound insulation, we simply take the noise we made in L1 and takeaway the noise we measured in L2, this gives us our sound insulation.
An impact sound insulation test is slightly different. We take what we call a ‘tapping machine’, which has 6 precise metal weights which drop from a very precise height onto the floor mimicking the effect of a child running very fast, and place the machine at 45 degrees to the axis of the room. The 45 degree axis is done to ensure the tapping machine isn’t placed directly onto a joist which could mask or dampen the noise. The tapping machine is eventually placed in 4 different positions too.
Because the tapping machine is highly calibrated and controlled, we only measure the noise it generates in the receive room. The building regulations stipulate how much of this noise is acceptable.
Both types of tests are then subject to two control measurements.
Background noise can often affect the noise in the receive room, as we are measuring at much lower noise levels. Machines and tools used on-site could in theory make the noise in the receive room higher which would give a false reading for the wall. It is important to keep the site as quiet as possible during measurements. Sometimes this will mean shutting a site down or testing out of hours to ensure a quiet site. We measure the background noise level in the receive room and can apply a small correction where some background noise does influence the test, however, this is limited to 6dB so any additional noise will be taken as poor performing walls.
But can’t I just fill the room with egg boxes to improve my sound insulation? It’s a common question but unfortunately not. We measure the reverberation time in the receive room very accurately for this exact reason. This means if the room happened to be filled with egg boxes or blankets or any other acoustic material, the adjustment is made in the calculation to remove the effect it would have.
Not all homes are subject to sound insulation testing. In all home nation building regulations requirements, a sample of plots are selected for testing. This does vary slightly for Scotland.
We tend to break up the number of tests we do into ‘sets’ comprising of 2 airborne floor tests, 2 airborne wall tests and 2 impact floor tests.
For apartments, the amount of tests in a set is as above:
2 airborne floor tests, 2 airborne wall tests and 2 impact floor tests.
For houses, the sets rule still applies, however, because there is no physical floor separations between neighbouring plots, only wall tests are conducted.
England, Wales and Northern Ireland Minimum Requirements
At least 1 set is conducted for each 10 examples per separating construction type.
For example, if we had a row of 12 houses, each with the same construction detail for the partition, we would conduct 4 airborne wall tests (2 sets). When calculating sets of tests, we always round up as one set of tests can be used for a maximum of 10 houses.
If we had 26 apartments, with identical partition construction throughout, we would conduct 18 sound insulation tests (3 sets) made up of 6 airborne wall tests, 6 airborne floor tests and 6 impact floor tests.
Scotland
Scotland Technical Handbook Section 5 has a slightly reduced requirement for the number of sound insulation tests conducted across a new-build site.
The number of tests depends directly on whether or not the Example Construction Types are used (see link here Example Construction Types – Scotland). Testing requirements are then calculated according to the following table:
| Construction Type | No of Attached Dwellings | No of tests for separating walls [houses] | No of tests for separating walls [flats or maisonettes] | No of tests for separating walls [flats or maisonettes] |
|---|---|---|---|---|
| New build using example construction | 2 - 20 | 2 | 2 | 2 |
| 21 - 40 | 3 | 3 | 3 | |
| Over 40 | 1 extra for every 20 houses, or part thereof | 1 extra for every 20 flats or maisonettes, or part thereof | 1 extra for every 20 flats or maisonettes, or part thereof |
|
| New build using other constructions | 2 - 20 | 2 | 2 | 2 |
| 11 - 20 | 3 | 3 | 3 | |
| 21 - 30 | 4 | 4 | 4 | |
| Over 30 | 1 extra for every 10 houses, or part thereof | 1 extra for every 10 flats or maisonettes, or part thereof | 1 extra for every 10 flats or maisonettes, or part thereof |
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The Sound Insulation Testing & Measurement Association
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