The need to carry out sound insulation testing to assess and report the acoustic performance of dividing partitions between dwellings has become increasingly important in order to demonstrate that a building’s intended performance is achieved when constructed.

Poor design detailing and/or onsite construction can have a significant impact on the overall performance of building elements and the building as a whole. Post completion sound testing provides greater certainty that designed performances are actually being achieved in compliance with Approved Document E.

Precompletion Sound Testing is now an integral part of supporting the completion certificate process throughout the UK and Ireland. In order to ensure that testing is undertaken within a robust regime which controls the reliability of test results, government guidance is in place which describes restrictions on those who should carry out sound testing and reportage.

Approved Document E states a set of sound tests should be carried out for every ten dwellings (houses, flats or rooms for residential purposes). However, if the development has several different construction types, you may need to carry out further tests for each type of construction.

For houses this usually means you are required to undertake 2 airborne wall sound tests (up to 10 houses) to the dividing walls. For flats you will be usually be required to undertake 2 airborne wall, 2 airborne floor and 2 impact floor tests (up to 10 Flats). When we undertake a fee proposal for clients, we always include a full testing schedule so it can be submitted to building control for their approval prior to the test date.  

One of the stipulations of Approved Document E is that the testing company needs to be UKAS accredited, this is covered under the Resistance to the passage of sound: Approved Document E [ADE] it goes on to state that “The person carrying out the building work should arrange for sound insulation testing to be carried out by a test body with appropriate third party accreditation” and is downloadable at: https://www.gov.uk/government/publications/resistance-to-sound-approved-document-e.

APT Sound Testing is UKAS accredited to carry out sound insulation testing and is laboratory and as a result our reports will be accepted by building control – here is a link to our UKAS Sound Testing Accreditation: https://www.ukas.com/wp-content/uploads/schedule_uploads/00002/4340Testing%20Multiple.pdf

For future note we are also UKAS accredited to carry out Air Tightness Testing – here is a link to our UKAS Air Tightness Accreditation: https://www.ukas.com/wp-content/uploads/schedule_uploads/00002/4340Testing%20Multiple.pdf

If you would like more information on our sound testing service and/or other services please contact us now at: info@aptsoundtesting.co.uk or visit our website at www.aptsoundtesting.co.uk.

Alternately, if you would like more information on how to prepare for your sound insulation testing please download our sound test checklist.

Airborne and Impact Sound is transmitted through most walls and floors by setting the entire structure into vibration. This vibration generates new sound waves of reduced intensity on the other side. The passage of sound into one room of a building from a source located in another room or outside the building is termed ”sound transmission”. 

Understanding Sound Testing
Sound transmission loss or Sound Reduction Index, R dB, is a measure of the effectiveness of a wall, floor, door, or another barrier in restricting the passage of sound. The sound transmission loss varies with frequency and the loss is usually greater at higher frequencies. The unit of measure of sound transmission loss is the decibel (dB). The higher the transmission loss of a wall, the better it functions as a barrier to the passage of unwanted noise across the dividing (acoustic) partitions.

Approved Document E stipulates that there are two types of sound insulation in buildings: airborne and impact. Airborne sound insulation is used when the sound produced directly into the air is insulated and it is determined by using the sound reduction index. Impact sound insulation is used for floating floors and it is determined by the sound pressure level in the adjacent room below.

A sound insulation test of a separating partition will be considered as a pass if the airborne sound insulation is equal to or greater than the DnT,w + Ctr value shown for the appropriate dwelling in the table, for airborne testing in new builds properties a figure of 45dB or greater is required and for Impact testing 62dB and below. For conversion properties a figure of 43dB or greater is required and for Impact testing 64dB and below.

What is DnT,w

DnT,w is an in-situ measured performance parameter that demonstrates the level of resistance to sound transmission between two adjacent spaces, such as flats or houses. The measurement will include both direct sound transmission and flanking sound transmission of the construction. Flanking transmission is the effect of sound travelling through the building and may be particularly evident where beams and joists bridge a common partition or along poorly isolated lightweight wall constructions.

The DnT,w of a separating wall or floor will typically be of the order 5 to 7 dB lower than the manufacturers specified Rw (single figure quantity of sound insulation) for the single element, due principally to the contribution from flanking sound transmission around the element when it is built on site – this should always be accounted for in the initial acoustic design.

What is Ctr

Ctr is the spectrum adaption term. It is a correction attributed to the sound insulation quantity to account for urban traffic noise.

What is L’nT,w

L’nT,w is an in-situ measured performance parameter that demonstrates the level of resistance to impact sound transmission between floors. The impact measurement includes both direct sound transmission and flanking sound transmission.

Weighted Sound Reduction Index Rw

When specifying the acoustic performance of an acoustic partition in a more general manner, it can be useful to describe the sound insulation by a single number. The weighted sound reduction index, Rw , is a rating method given in EN ISO 717-1. This standard fits a standard reference curve to the measured sound reduction index curve.

Within the EN ISO 717-1 standard, a rating method is also given where the Rw value is completed by two C-terms which are applied to two models of the noise spectra for various types of noise. These two terms, Rw + C and Rw + Ctr, also include the frequency range 100 – 3150 Hz but can be extended to 50 – 5000 Hz. As industrial and traffic noise often have high sound levels which are also below 100 Hz, it is recommended that the extended frequency area is used.

The summary value, Rw + C, gives the reduction value in dBA for a spectrum with a level that is equally high in all third-octave bands. This can be used for:

•             Highway road traffic travelling at speeds in excess of 80 km/h

•             Factories emitting mainly medium and high-frequency noise

•             Living activities (talking, music, radio, TV)

•             Railway traffic at medium and high speed

•             Jet aircraft at a short distance

The summary value Rw + Ctr also gives the reduction value in dBA, spectrum with low-frequency dominance such as:

•             Disco music

•             Urban road traffic

•             Railway traffic at low speeds

•             Factories emitting mainly low and medium-frequency noise

Both the impact and airborne insulation performance of floors and walls should be carefully considered from the start of the project to ensure that the minimum performance requirements for new and converted developments are met in line with Approved Document E

If you would like more information in regard to our sound testing and/or noise survey services, please contact us now at info@aptsoundtesting.co.uk or call 01525 303 905 today.