Month: March 2021

Sound Testing for New Build Dwellings

Sound Testing for New Build Dwellings

Sound Testing Services for New Build Dwellings
Sound Insulation Testing became mandatory in England & Wales in 2003, when Approved Document E was updated. Approved Document E requires new and converted to achieve a reasonable level of sound insulation between dwellings. The simplest way to comply with the requirements of Approved Document E; is to have on-site pre-completion sound insulation tests carried out on your project. We carry out full sound testing services in compliance with Approved Document E.

In our experience there is usually a level of apprehension with our clients having to undertake pre-completion sound insulation tests.  This is often down to the fear of failure. It should be remembered; however, that if the acoustic design specification is closely followed, and a good standard of onsite workmanship is maintained there is very little chance of failure.

Sound Testing for New Build Dwellings

Sound Testing New Build

Approved Document E requires a minimum of one ‘set’ of tests for every ten units in each group and/or sub group.  Is usually broken down to the following: two airborne wall, two airborne floor and two impact sound tests. For example, if you have a block of 100 flats, all of the same construction, you would usually conduct 10 ‘sets’ of tests. If you have a development of 25 houses, with five different sub-groups (5 units in each) then you would usually conduct 5 ‘sets’ of tests.  As previously stated a set of tests usually consists of two airborne tests of separating walls and two airborne tests and two impact tests on separating floors; however, if no separating floors are available, i.e. in semi-detached or terraced houses, one set of tests would consist of two airborne tests of separating walls only.

To test the airborne sound insulation properties of a floor or wall, a sound source which consists of an amplifier and loud speaker is set up on one side of the wall or floor partition that is to be tested. We then turn the setting to turn on Pink noise. Pink noise sounds like the static that can be heard on a radio that is off station or the old TV test card noise.

This type of noise is used because it is made up of a wall of sound that has a wide spectrum of frequencies. This provides an indication of sound insulation performance for a wide range of sounds that may be experienced within a dwelling from speech to a kettle boiling. The pink noise is measured in the room which contains the speaker or sound source using a Class 1 Norsonic sound level meter; thereafter the noise is measured on the other side of the wall or floor partition that is being tested. In layman’s terms the difference between these two levels is the amount of sound that is stopped by the sound insulating qualities if the wall or floor partition/s.

The result is then corrected and adjusted depending on the echo or reverberation time within the receiving room, and any background noise such as builders work noise etc. to give the airborne sound insulation result (DnT,w). The results of these tests are then compared to the performance criteria of Approved Document E – 45dB new build & 62dB for conversions) and a pass or fail sound test certificate is produced

Testing Impact Sound Insulation Performance
To test the impact sound insulation performance of a floor, a Norsonic tapping machine which consists of five small hammers that are dropped onto the floor to simulate foot fall, is placed on the floor. The resultant noise in the room below is measured with a Norsonic Class 1 sound level meter and the amount of noise that passes through the floor is the impact sound transmission level and is expressed as a single number. This result is then corrected and adjusted depending on the reverberation time of the rooms as well as any background noise to give the impact sound transmission result (LnT,w). The results of these tests are then compared to the performance criteria of Approved Document E – 62dB new build & 64dB conversions) and a pass or fail sound testing certificate is produced.

If pre-completion test results do not satisfy the performance criteria of Approved Document E, then our test engineer will attempt to determine the possible causes of failure. This may be to do with construction detailing around services or at junctions, or simply, poor acoustic design. Once the results have been finalised along with the associated graphs, our acoustician (with the aid of the information from the sound test engineer, we should be able to determine the specific cause of failure. Once a specific reason for failure has been determined, we can then advise the client on remedial actions that can be undertaken. Contact APT Sound Testing

If you have a project that’s needs acoustic design advice or needs pre-completion sound testing then please contact us by visiting the  APT Sound Testing Website and we should be able to offer you an acoustic solution to help your project achieve practical completion.

Steps for a Planning Noise Assessment

Steps for a Planning Noise Assessment

The 5 Simple Steps for a Planning Noise Assessment

1st Step – Baseline situation

It will usually be necessary to have a full understanding of the existing noise levels in the vicinity of the receptor. This can be achieved by carrying out a planning noise survey of background or ambient noise levels over the period when the noise source will be operational.

The baseline noise levels will usually be determined by measuring the LA90 or the LAeq, however in practice both will usually be measured simultaneously.

The term ‘LA90’ is the ‘A’ weighted noise level exceeded for 90% of the measurement period. Typically this is called the background noise level if it relates to a period when the noise source is not operational.

The ‘A’ weighting is a correction applied within a sound level meter to adjust the response of the Class A noise meter to match the response of human hearing at different frequencies. This is used to exclude short-term noises, such as a vehicle passing from the measurement value, leaving only the underlying or background noise.

The terms ‘LAeq’ is as an average noise level over the measurement period, although it relates to the average noise energy. It is a popular and universally used measure which correlates well with human annoyance.

Step 2 – Noise sources and times of operation

A detailed knowledge of the noise source (or in the case of a proposed development, the likely noise source) is also essential. This is because noise levels are of less importance than the amount by which they exceed the baseline noise and the times or days of operation.

Step 3 – Manufacturer Data for Proposed Equipment

If the proposed development will create a source of noise, the noise consultant may need the manufacturer’s data for proposed equipment, times of operation and working practices.

Step 4 – Determining the impact

Noise impact is determined using a variety of methods, all of which will rely on comparing noise levels at a receptor against absolute noise level criteria or against existing baseline noise levels. Generally one of three approaches is used:

  1. Where the proposal is for a development which will introduce an industrial type noise source, or where a receptor in a new development may be affected by this type of source, it is usual to assess impact by comparing the noise level, after making corrections for certain attributes of the noise, against background noise levels at the receptor (existing or proposed). The council expects that, at the receptor, noise from the source is a certain amount below existing background levels. Typical cases include new equipment in a business, an air conditioning unit or an extract and fan serving a restaurant. This is known as the BS4142 methodology.
  2. In some cases the impact does not depend on a comparison between source levels and baseline levels. For example, a proposed housing development is close to an existing road, where generally the impact is determined by establishing whether the absolute levels due to the source are acceptable.
  3. Applications for certain developments may require a more specialist approach. For example, the method for assessing a new nightclub combines both elements. Existing levels of noise in low frequency bands are measured and compared against levels in those same frequencies with music playing. The council may then require that the music does not cause any increase above existing levels.

Step 5 – Noise mitigation measures

Development proposals which are inherently noisy may include mitigation measures in the original scheme. However, the need for further mitigation may be necessary when the impact assessment indicates that the acceptability criteria are exceeded. Either way noise mitigation, or reduction measures, should be considered in the assessment in demonstrating how the acceptability criteria will be achieved.

The most effective measures will be those which reduce levels at source, rather than in transmission or at the receptor. However, in situations such as where the proposal is for new housing near existing sources of noise, it will not be possible to reduce source noise levels. Where the proposal will introduce a new noise source it is good practice to reduce levels at source as far as possible, before considering other mitigation measures, some of these may be:

  1. Reduction of noise at source – Using equipment or systems with lower sound power levels is highly effective and can avoid the need for other more costly and intrusive mitigation options. Noise impact can be lessened by reducing total running times or by shifting operations to less sensitive times of the day. The use of acoustic silencers and enclosures around the source may also be effective at reducing the need for other mitigation methods.
  • Reduction of noise in transmission – The simplest way to reduce noise once emitted is by increasing the distance to receptors. For example, siting of plant and equipment within an industrial site as far away from sensitive receptors as possible and/or the new housing development may be designed so that properties are set back from a noise source. In many cases, a properly calculated buffer zone between source and receptor will represent the most cost effective solution.
  • Reduction of noise at a receptor –  if the development is located in a busy urban area, this may be the only option to reduce the noise impact, also where the applicant has no access to land for the construction of a barrier. The way a development is designed can be an effective mitigation tool if the building faces away from the main noise source. Also, if noise sensitive rooms are located on the sheltered side of the building, the impact will be reduced at the most sensitive areas.
  • Acoustic Improvements to the building façade – Where no other options are available, improving the sound insulation of a building facade can be effective in reducing internal noise levels. However, often it will be necessary to provide acoustic treated mechanical ventilation to avoid the need to open windows in warm or humid weather, this is often the solution next to busy elevated railway lines.

If you would like more information in regards to our noise surveys for planning and acoustic design for your development, please visit the APT Sound Testing website or call us today on: 07775 623464.