Sound insulation testing is required to make sure that a residential development can demonstrate acceptable levels of noise attenuation performance. Building Regulations Part E requires you undertake two different types of sound testing including airborne noise (i.e. sound/noise transmitted through the air, such as televisions and conversations between people) and impact noise (i.e. noise resulting from an impact on the floor surface, such as footsteps on the floor). By undertaking the two types of sound testing ensures the dwelling provides a reasonable resistance to the passage of sound.

Part E of the Building Regulations for England and Wales, requires that various walls and floors are tested between adjoining dwellings. The exact number of walls requiring testing will vary depending on the overall size of the development and the amount of different types of wall or floor constructions. On a typical small to medium development consisting of up to 10 dwellings with the same partition construction should require 1 x 6 pack, which consists of 2 airborne wall tests, 2 airborne floor tests and 2 impact floor tests.

In most cases the rooms to be sound tested will be the two main habitable rooms which would be living rooms and bedrooms. The sound test procedure involves setting up a noise source in a room on one side of the party wall or floor and measuring the noise on both sides of the partition.

If you are unsure of the amount of tests required on your project, the guidance contained within Approved Document E can be very helpful as it gives detailed recommendations for the partitions to be tested and for the number of sound tests that should be carried out. We recommend that the proposed sound testing is agreed in advance with the Building Control Officer and/or persons requiring the sound test.

It is worth noting that when we carry out a quotation for clients it usually contains a full schedule of sound tests to comply with Building Regulation Part E; you can then table the schedule to your approved inspector to check that its acceptable prior to the testing. We also send out an informative checklist to help you prepare for your sound testing.

Our sound test schedule will look similar to this:

Airborne Wall

• Plot 1 Lounge to Plot 2 Lounge
• Plot 1 Bedroom to Plot 2 Bedroom

Airborne Floor

• Plot 1 Lounge to Plot 3 Lounge
• Plot 1 Bedroom to Plot 3 Bedroom

Impact Floor

• Plot 3 Lounge to Plot 1 Lounge
• Plot 3 Bedroom to Plot 1 Bedroom

For us to undertake accurate sound testing we require that certain guidelines are followed, such as keeping site noise levels to be kept to a minimum etc. Any site operatives working in the testing area will have to leave temporarily and any noisy works in the vicinity of the test areas such as groundworks, drilling and banging will need to be suspended.

We always provide a full sound testing checklist within our quotation which identifies what actions need to be undertaken to prepare for the sound insulation testing.

The preparation of the buildings/dwelling is very important, as they can influence the results of the test. The following stages for sound testing will help preparation and also assess the point at which completed buildings can be tested. Generally before the test the parts of the building/rooms either side of the separating wall or separating floor should be complete. Particular attention should be paid to the following:

1. All separating floors and walls and all flanking walls and floors should be complete.
2. All wall and floor junctions should be complete – to include flanking strips etc.
3. All wall finishes should be complete, this should include skirting’s being in place. This does not include decorative finishes such as paint.
4. Floors must be bare and no carpets should be laid – where a concrete floor with bonded resilient cover is to be fitted with wood based flooring. In this case, the test sample resilient floor cover should be tested with a wood based floor covering laid over the test sample area.
5. Windows should be installed with all glass fitted.
6. Trickle vents should be in place and closed.
7. All doors should be fully fitted and closed. This includes internal doors and external doors fully fitted with doors seals.
8. Services should be complete and any voids around ducts finished.
9. Electrical sockets should be fitted.
10. A 240V electricity supply should be available to all the test plots.
11. There should be no noise during the test other than from the testing equipment.
12. The test plots and adjacent areas within the building should be quiet for the duration of the test.
13. No work should be carried out or noise made in the building at the time of the test.
14. Site workers should not enter the building or be in the parts of the building undergoing a test.

To try and help our clients achieve compliance with Approved Document E, we offer the following 4 step acoustic design advice package:

1. Site Survey Visits – to let us view the existing site construction. This allows us to check for potential problematic construction such as inclusion of lightweight blocks in the existing construction. It also lets us check that the installation teams are installing the acoustic materials as per manufacturer’s guidelines.

2. Sample Sound Testing – of the existing construction. This offers an accurate overview of the acoustic performance of the existing partitions which enables us to offer a targeted acoustic design using the sound insulation performance of the existing construction.

3. Acoustic Design Review – a full design review of the proposed developments party walls and floors. Site Survey Visits – to let us view the existing site construction. This allows us to check for potential problematic construction such as inclusion of lightweight blocks in the existing construction. It also lets us check that the installation teams are installing the acoustic materials as per manufacturer’s guidelines.

4. Pre-completion Sound Testing to satisfy Approved Document E.

Our clients have never failed their pre-completion sound testing when they have employed our Four Step Acoustic Package.

The test duration depends on the amount of tests required on the project. Taking into account standard site conditions a set of sound tests on houses – two airborne walls tests will take one to two hours. A standard six pack of tests for flats, consisting of two airborne walls, two airborne floor and two impact tests will take between two to three hours. For every 6 tests thereafter will be another 2-3 hours. If the site conditions are agreeable we can undertake up to 18 sound tests in one day; however, to allow this to happen we will require full free uninterrupted access to the units/rooms in all test areas.

1. Why am I required to undertake sound insulation testing?

Sound insulation and speech privacy are critical for a variety of reasons. Inadequate sound insulation can be extremely distressing to those affected by it and may lead no major noise disputes and legal actions. For example, in an apartment block, your upstairs neighbour may like playing loud music. However, the downstairs occupant may be working nights and sleeping throughout the day, thus any inadequate sound insulation between these two flats would cause great disturbance and distress to the downstairs occupants.

2. What is pre-completion sound insulation testing?

Pre-completion sound testing is a building regulation requirement for all new build and dwellings formed by ‘material change of use”, i.e. conversion projects. It has been a requirement that you undertake sound testing on dwellings since 2003. Sound testing should be undertaken to 10% of properties in each development to ensure that the separating walls & floors between habitable rooms of neighbouring properties meet the minimum requirements as defined by Approved Document E, commonly referred to as Approved Document E; for instance:

• For a pair of semi-detached Houses – a set of tests would usually comprise two airborne sound insulation tests of a separating wall.
• For Flats (up to 10 units) – a six pack would normally be required, this comprises of: two airborne wall tests, two airborne floor tests and two impact floor sound tests. The easiest way to work out the number of tests required is to multiply 1 x 6 packs for every 10 flats, i.e. if you have 22 flats you will require 3 x 6 packs which equals 18 sound tests in total.
• For Rooms for Residential Purposes (up to 10 rooms) (student accommodation, hotel rooms, care homes etc.) – a set of tests would usually comprise: one airborne sound insulation tests of a separating wall; one airborne sound insulation test of a separating floor; one impact sound transmission test of a separating floor.

3. How are plots selected for sound testing?

APT usually specifies the amount of sound insulation tests that are required. Firstly we look through the floor plans to work out a testing schedule taking into account the positioning of habitable rooms, the room and partitions sizes. We always tests through ‘habitable rooms’ partitions i.e. lounges & bedrooms wherever possible. We will also try and undertake testing across walls and floors in different areas of the building and through different partition types i.e. if one wall is made of masonry and the other met-sec partitioning. Once we have specified the sound testing schedule, the client should show building control to seek their approval before the commencement of the sound testing.

4. What are the minimum requirements for separating party walls and floors?

The minimum requirements of ADE can depend on a variety of factors such as if the development is new build or refurbished, whether the development is intended to be a permanent dwelling, or classified as “rooms of residential purposes” (e.g. hotels, student accommodation, etc). A brief summary of the minimum requirements can be found below:

DWELLING HOUSES AND FLATS		Airborne standard DnTw,w+Ctr dB	Impact Standard L’nT,w dB
Purpose built dwellings	Walls	at least 45	N/A
	Floors and Stairs	at least 45	up to 62
Dwelling formed by material change of use	Walls	at least 43	N/A
	Floors and Stairs	at least 43	up to 64

5. How is sound insulation testing carried out?

For airborne wall and floor sound tests, two individual speaker positions are used for each source room; with a total of ten individual 1/3 octave band measurements recorded for both the source and receiver rooms. Measurements are then made to monitor the levels in the receiving room of the tested partition in question. This gives a basic level difference between source and receiver rooms. This basic level difference is then ‘corrected’ to allow for the reverberation time (the time taken, in seconds, for a noise source to decay by 60 dB) and the existing levels of background noise monitored whilst in the receiving room.

All our tests are carried out in full accordance with BS EN ISO 140-1998 parts 4 (airborne sound testing) and 7 (impact sound testing), and the calculation of all single figure results are done so in accordance with BS EN ISO 717:1.

6. How do I know when my site is ready for testing?

Sound testing is typically conducted when a development nears completion, and once all internal and external doors and windows have been fitted, it is worth noting that no carpets should be installed prior to the sound testing.

To be able to conduct sound insulation testing we a constant supply of 240V power; we cannot use generator power. We also require a quiet site (a noisy site can make conducting the tests extremely difficult), so no drilling, jack hammers etc. should be used whilst the testing is taking place. We also require full access to all rooms to either side of the dividing partition so if it is a requirement to access a neighbour’s property, this must be arranged prior to the test date.

7. Do you offer acoustic advice to help me pass my sound insulation test?

Yes, we can offer an acoustic design service to help you design your buildings partitions to pass Part E sound testing. If you send through the relevant drawings such as sections and floor plans during the design stages of the project, we can check the design is adequate and if there appears to be any junctions or details where ‘noise flanking’ may occur, we can then advise if any changes are required to lower the chance of sound test failures..

8. Why am I required to undertake sound insulation testing?

Sound insulation and speech privacy are critical for a variety of reasons. Inadequate sound insulation can be extremely distressing to those affected by it and may lead no major noise disputes and legal actions. For example, in an apartment block, your upstairs neighbour may like playing loud music. However, the downstairs occupant may be working nights and sleeping throughout the day, thus any inadequate sound insulation between these two flats would cause great disturbance and distress to the downstairs occupants.

One explanation of airborne sound is as follows; when a sound wave is incidental upon a partition between two dwellings, part of it is reflected and part of it is transmitted through the wall of floor partition.

For single leaf structures, such as dense masonry brickwork, the transmission follows the mass law, i.e. the more massive the structure, the smaller the quantity of transmitted sound.

For lightweight structures consisting of multiple layers, such as a twin met-sec gypsum wall, the spring-mass law is applicable. If highly absorbent material such as acoustic insulation is used within the construction of a double leaf wall, the sound insulation improves. The wider the cavity, the greater the benefit from stone wool will be. If a cavity has been filled with acoustic wool your sound test result should typically improve by 5 – 10 dB.

Airborne sound testing is undertaken to walls & floors. Firstly a controlled noise is generated by an amplifier and loudspeaker across a broad range of frequencies. The generated noise is very loud and is often in excess of 100dB. Initial measurements are taken using a class 1 sound level meter within the ‘source room’ followed by further measurements in the ‘receiver room’ on the other side of the wall or floor under investigation. The source room speaker position is then changed and the measurements repeated either side of the partition under test.

Thereafter background noise measurements are made using a class 1 sound level meter in the receiving room and are used to apply appropriate corrections for external sound such as traffic noise. Similarly the reverberation time (the time taken for sound to decay by 60dB) is measured within the receiving room using the sound source and a sound level meter to determine the corrections that must be applied to account for the characteristics and absorptiveness of the room.

The difference in the two airborne noise levels (for walls and floors), corrected for background and reverberation characteristics determines the airborne sound insulation performance of the wall, or floor. A greater airborne noise difference between the source room and the receiver room determines a higher airborne sound insulation performance.

An impact sound source sets up vibrations directly in the element it strikes whereas an airborne source sets up vibrations in the surrounding air which spread out and, in turn, set up vibrations in the enclosing walls and floors partitions.

The impact vibrations spread out over the whole partition/s and into elements connected to it, such as internal walls and floors as well as the inner leaves of external walls. The vibrations in the wall/floor elements force the air beside them to vibrate and it is these new airborne vibrations that are heard.

In most cases a floor depends on its mass to reduce airborne sound and on the soft covering to reduce impact sound at source – this often confuses people.

Using an acoustic membrane such as a Regupol multi will largely isolates the walking surface from the base and should improve the impact and to a lesser extend the airborne sound insulation results.

Impact sound transmission testing is undertaken to floors only. This actual methodology behind the test is different to airborne as a calibrated Norsonic ‘tapping machine’ is used for the test, which comprises of five ‘hammers’ driven up and down by a cam and electric motor is used to “tap” the floor surface by applying a known force on the floor structure. The machine is placed in several pre-determined positions. The resulting noise is measured in the dwelling below, using a sound level meter.

Thereafter, background noise measurements are made using a class 1 sound level meter in the receiving room and are used to apply appropriate corrections for external sound such as traffic noise. Similarly the reverberation time (the time taken for sound to decay by 60dB) is measured within the receiving room using the sound source and a sound level meter to determine the corrections that must be applied to allow for the characteristics and absorptiveness of the room.

The measured noise levels in the receiving room are corrected for background and reverberation characteristics determine the impact sound insulation performance of the floor. For the impact noise the lower the measured level, the better the performance as less sound is being transmitted into the dwelling below.

Noise flanking (or flanking sound) is sound that transmits between spaces indirectly, i.e. it travels around the edge of materials rather than passing directly through the main separating wall and/or floor partitions.

Unfortunately this may result in a sound test failure even if the main separating element itself is robust and provides good acoustic insulation. Noise flanking can result from both impact sounds and airborne sounds. Any building element that penetrates or circumnavigates a separating element can result in flanking.

To help consultants and contractors we have comprised a list of the most common noise flanking paths:

• Dividing Floor Partitions – Through Floor and Floor Joist Space (if insulation has not been installed or direct fixing to joists without a drop ceiling below the partition under test)
• Dividing Ceiling Partitions – Above and Through the Ceiling Space (where an adequate acoustic break has not been carried on through the ceiling void)
• Shared Structural Building Components – Floor Boards, Floor Joists, Continuous Drywall Partitions, Continuous Concrete Floors, and Cement Block Walls.
• Through Structural Steel (structural steel beams are often a major cause of noise transmission as plasterboard is often fixed directly to the steel without sound breaks)
• Plumbing Chases – Junctures between the Walls & Floor Slab Above or at the Exterior Wall Juncture (this should be filed with mortar etc. to add mass to this weakened areas.
• Through Windows (if they are no double glazed or have secondary glazing as a minimum)
• Fixtures & Outlets – Light Switches, Telephone Outlets, and Recessed Lighting Fixtures (if penetrations have been cut back to back with the opposite dwelling under test)
• Ductwork and pipework – this often runs through the acoustic partition from dwelling to dwelling, especially in new apartment construction.
• Structural Joints – Perimeter Joints at Wall & Floor, Through Wall & Ceiling Junctures (these should be filled with acoustic mastic.
• Around the End of the Partition Through the Adjacent Wall (acoustic mastic should be used to seal this junction)
• Poor workmanship – can cause noise flanking as operatives are often in a rush to construct the acoustic partitions etc. which often means the incorrect fixings are during the construction process.

Within building regulations Approved Document E: Resistance to the passage of sound, it clearly defines ‘flanking transmission’ as, ‘Sound transmitted between rooms via flanking elements instead of directly through separating elements or along any path other than the direct path’. It defines a ‘flanking element’ as, ‘any building element that contributes to sound transmission between rooms in a building that is not a separating floor or separating wall’.

Noise flanking should be considered during the design stage of new projects and good acoustic detailing should eliminate or minimise the inadvertent downgrading of sound insulation. in many cases, junctions between elements can offer a potential flanking route if they are not carefully detailed and constructed. Good briefing and ongoing supervision during the construction phase can help to ensure that the quality of workmanship remains high so that details are constructed as designed.

In many cases the location and layout of rooms within developments will play an important role in relation to the levels of subsequent ambient or background noise that may surround the occupant/s. In most cases much of noise is transmitted through the dividing wall and floor partitions between habitable dwellings, such as flats and terrace houses.

If neighbours have varied working patterns, i.e. they work night shifts and arrive back in the early hours of the morning, i.e. the layout of the rooms use of rooms are particularly important.

Main ‘habitable’ rooms such as Kitchens or living rooms, which back onto bedrooms of the adjacent dwelling, are more likely to lead to noise complaints. Kitchen cupboards doors may transmit impact noise through the wall partition into the bedroom next door; this can lead to annoyance and frustration for the neighbour and subsequent noise complaints.

To reduce the chance of noise complaints, wherever possible hallways/corridors should be placed alongside the adjacent property i.e. back to back, to reduce the chance of noise transference and reduce the risk of sound test failure. Failing this a kitchen should be placed against a kitchen and bedrooms should back onto other bedrooms.
Planning a good acoustically favourable dwelling layout can help to reduce the number of noise problems that will occur even if your building passes the Part E Sound Insulation Testing.

We often find that confusion can arise from the large amount of ‘acoustic terms’ used in conjunction with acoustic design and sound insulation testing. To help with this we have made a list of the following terms for clarity:

Absorption

This is the conversion of sound energy into heat, often by the use of a porous material.

Absorbent Material

This is a material that absorbs sound energy, such as acoustic mineral wool.

Airborne sound

This is sound which is propagated from a noise source through the medium of air. Examples of these are speech and sound from a television

Airborne Sound Transmission

This is direct transmission of airborne sound through walls or floors. When sound energy is created in a room, for instance by conversation, some of the energy is reflected or absorbed by room surfaces but some may set up vibrations in the walls and floor. Depending on both the amount of energy and the type of construction, this can result in sound being transmitted to adjacent parts of the building.

Air Path

This is a void in construction elements, which adversely affects the performance of sound resisting construction. Examples of air paths include incomplete mortar joints, porous building materials, gaps around pipes and shrinkage cracks – this can also effect the air tightness results.

Bonded resilient cover

This is a thin resilient floor covering normally of minimum 3-5mm thickness, which is bonded to the isolated screed surface to reduce impact sound transmission such as footfall noise, however it has a lesser effect when it comes to airborne noise.

Cavity stop

This is a proprietary product or material such as mineral wool (fibre) used to close the gap in a cavity wall.

Composite Resilient Batten

This is composed of a timber batten with a pre-bonded resilient material to provide isolation between the flooring surface layers and floor base.

Cradle/Saddle

This is an intermediate support system (with a resilient layer base, either pre-bonded or already integral) using levelling packer pieces to support a timber batten, isolating it from the floor base.

Decibel (dB)

This is the unit used for different acoustic quantities to indicate the level with respect to a reference level.

Density (kg/m3)

This is the mass per unit volume, expressed in kilograms per cubic metre (kg/m3). Blockwork is commonly referred to by industry in terms of strength (in Newtons). However, it is the density that has the important role in terms of sound insulation.

Direct transmission refers to the path of either airborne or impact sound through elements of construction.

DnT,w

This is the weighted standardized level difference. A single-number quantity (weighted) which characterises the airborne sound insulation between two rooms, in accordance with BS EN ISO 717-1:1997

Façade Testing

This Standard – ISO 140-5:1998) specifies the testing methods to evaluate the sound insulation in buildings and building elements for facades. Three rounds of a proficiency testing scheme for airborne sound insulation measurements have been performed according to the methods specified in the standard for a whole facade by using an external loudspeaker as the noise source.

Flanking element (flanking wall)

This is any building element that contributes to the airborne sound or impact transmission between rooms in a building which is not the direct separating element (i.e. not the separating wall or separating floor).

Flanking strip or edge strip

This is a resilient strip using foamed polyethylene normally 5 mm thick, which is located at the perimeter of a floor to isolate the floor boards from the walls and skirtings.

Flanking transmission

This is airborne or impact transmission between rooms that is transmitted via flanking elements and/or flanking elements in conjunction with the main separating elements. An example of a flanking element is the inner leaf of an external wall that connects to the separating ‘core’ of a wall or floor.

Flexible closer

This is a flexible cavity stop or cavity barrier which seals the air path in cavities linking adjoining dwellings.

Floating floor treatment (FFT)

This is a timber floating floor system which may use battens, cradles or platform base, all of which use a resilient layer to provide isolation from the base floor and adjacent wall elements.

Gypsum based plasterboard

This is a dry lining board applied to walls, ceilings and within floating floor treatments which has gypsum content. It may also have fibre reinforcement within the board.

Impact sound

This is sound which is propagated from a noise source through a direct medium. An example of this is footfall on a floor.

Impact sound transmission

This is sound which is spread from an impact noise source in direct contact with a building element.

Isolation

This is a strategy to limit the number and type of rigid connections between elements of construction.

L’nT,w

This is the weighted standardized impact sound pressure level. A single-number quantity (weighted) to characterise the impact sound insulation of floors, in accordance with BS EN ISO 717-2: 1997.

Mass

This is a physical quantity that expresses the amount of matter in a body. Walls and floors may be described in terms of the surface density (mass per unit area, kg/m2) of the wall face or the floor surface, which is the sum of the surface densities of each component of the construction. The density of materials is expressed as mass per unit volume, kg/m3, which can be provided via the core structure and linings such as in-situ concrete or solid dense block walls.

Mass per unit area (or surface density)

This is is expressed in terms of kilograms per square metre (kg/m2). This is often used to describe boards, panels, flooring and dry linings (see gypsum based board).

Resilience

This can reduce structural vibration transmission and still maintain material performance and overall dimensions, examples include floating floor treatments such as resilient battens or cradles, or resilient ceiling bars.

Resilient ceiling bars

This acoustic solution is generally metal based and vary in thickness from 11 mm to 30 mm. They are mounted perpendicular to the joist span direction and can increase both airborne and impact sound insulation. Care should be taken to ensure that the ceiling board fixings into the resilient bar do not come into contact with the joists and reduce the potential performance.

Resilient noggin

This is a small section of resilient ceiling bar which is used to assist in bracing non load bearing partitions.

Rw

This is a single-number quantity (weighted) which characterises the airborne sound insulation of a building element from measurements undertaken in a laboratory, in accordance with BS EN ISO 717-1: 1997

Sound Insulation Testing

Sound Insulation Testing is required near the end of a development to show that the performance of the party wall and floor partitions meet the standards as stipulated in Building Regulations Approved Document E. The testing methods for airborne and impact sound insulation is in full accordance with the suggested methods presented in BS EN ISO 140-parts 4 & 7: 1998.

Stiffness

This is can improve low frequency sound insulation, for example in floors, by reducing the potential for deflection or movement of the primary structure, therefore the correct spacing and depth of joists is important.