Dealing With Noise Flanking Issues

Dealing With Noise Flanking Issues 

One of the easiest ways of dealing with noise flanking issues is to use isolation strips around the perimeter of the partitions at the edges of floors and walls. Acoustic sealant should also be incorporated wherever possible. One of the main reasons for flanking sound test failures is when the inner leaf of the perimeter wall is built with light weight blocks. This acts like a large snare drum and the sound simple travels straight up the wall from one flat to the flat above and/or below. Even if you have used a acoustically robust wall and/or floor partition the sound insulation testing may still fail. If you have used lightweight blocks in your onsite construction and the building fails the sound testing you may need to construction independent internal plasterboard lining throughout the inner perimeter wall, this should isolate the lightweight blocks and ensure the flanking path is minimized.

This video shows noise flanking through a window reveal.

To reduce the chance of sound insulation test failures, it is imperative that flanking transmission is considered at the design stage and any construction detailing is specified to minimise any potential of noise flanking which will downgrade the acoustic performance. Good detailing at the design stage will minimise this effect and optimise the overall levels of acoustic privacy achieved. If designing for residential units, design advice on flanking details must be followed to maximise the possibility of achieving the specified acoustic performance. It is imperative that the design advice is followed, otherwise the site sound insulation values may not meet the performance criteria required and subsequent expensive remedial treatment may be required.

 If the onsite construction has gaps, cracks or holes it will conduct airborne sounds and can significantly reduce the sound insulation of a construction. For optimum sound insulation a construction must be airtight. Most small gaps can be sealed at the finishing stage using Gyproc jointing compounds. Small gaps or air paths around perimeter Gypframe framework can be sealed with sealant. At the base of the partition, gaps will occur which can be filled with acoustic mastic.

 If you would like more information in regards to sound insulation testing and or acoustic design advice, then please call us now at or call us on 07775623464.

Failed a Sound Test?

Failed a Sound Test?

If a client has failed a sound test, they often ask us for the reason why. It is almost certainly the result of a combination, of the following items:

  • Poor acoustic advice
  • Poor onsite installation
  • Flanking noise which comprises the sound insulating element.

Unfortunately, if you fail the sound testing its not easily rectified, as it usually means a major upgrade to the failed partition and thereafter another sound insulation test, which is both costly and time consuming.

If you do find yourself in this unfortunate situation, the first thing to do is contact APT Sound Testing your ‘friendly acoustic consultant’. We will be able to advise you on how to undertake minor acoustic upgrades, once we have obtained a copy of the failed sound test report. We can then ascertain the potential weak acoustic elements from the graphical results, and advise on a robust acoustic solution to building regulations Part E.

We will also be happy to liaise with your architect to ensure that all areas have been covered in the initial/remedial acoustic design. For a small fee we can visit site and undertake an ‘onsite design review’; or, do a an office based design review which cuts costs even further – to do this we would need all plans and sections relating to the project.


Problems with airborne and structure borne sound are often associated with direct flanking transmissions through floors, supporting walls and other associated structures. You need to establish if your problem is due to direct transmission, flanking transmission or a combination of both so that the most effective remedial treatment can be chosen to suit.

First you need to understand how the sound is travelling into your home. It may be coming directly through the separating partition, i.e. wall or floor or it may be coming along another indirect route – called a noise flanking path. The most common such flanking path is the inner leaf of an external cavity wall.

If you have suffered a sound test failure and/or you require acoustic design advice then please email us in phone our design manager Darren on 07775623464. We have the experience, professionalism and acoustic know how to ensure that your project can achieve Part E of Building Regulations.



London is a massive city containing over 8 million people. In this overcrowded environment it is essential that noise transference between adjoining properties in kept to a minimum for the occupant’s well being.

When there are problems with noise transference between dwellings, and the building’s design is called into question, we can offer advice on how to upgrade the wall and/or wall partition to improve the sound insulation values.

We have extensive knowledge regarding the way different materials and construction methods can influence the results of a sound test and subsequent noise transference, this helps to ensure your company achieves compliance with the Sound Testing for Part E of Building Regulations at pre completion stage.

Pre completion sound testing in London has been a mandatory requirement since July 2003. All new build properties and conversions which were built after this date require 10% of each party wall/floor construction type to be tested. Sound insulation testing is to be carried out between pairs of rooms separated by party walls and/or floors. In is usual to test between living rooms and bedrooms as these are classed as the two main habitable rooms; however, other rooms can be used if this is not possible such as study’s, kitchens and dining rooms.

Also, we are also experiencing a rise in the amount of sound testing that’s required to existing London buildings which isn’t surprising as the amounts of noise complaints to councils has doubled in the last 10 years, as a result we have carried out a large amount of sound tests in council/housing association blocks, where the residents are experiencing excess noise between the dividing wall and floor partitions.

We also undertake sound testing to existing flats where the lease stipulates that wooden floors should not be used instead of carpets and as a result of the change of floor finishes the noise levels have increased through the floors – especially the impact noise.  In all these instances we can undertake sound testing to highlight the existing noise levels so acoustic upgrades – if required) can be targeted and implemented, i.e. it may be as simple as installing an acoustic membrane on the floors below the timber floor.

sound testing equipment

The airborne sound testing is undertaken by using a sound source, amplifier and loudspeaker to generate a high noise level in one room (the source room). Noise measurements are then taken in both the source and receiver rooms using a prescribed number of source and microphone positions. The background levels in the receiver room are measured and the reverberation time in the receiver room is also measured. From the results the airborne sound insulation (DnT,w + Ctr) is calculated and compared to the requirements of Approved Document E.

For vertically separated rooms, another type of sound test called Impact sound testing may also be required. This sound test is undertaken using a tapping machine which drops a series of weights onto the floor of the upper room. The noise level in the lower (receiver) room is measured for a prescribed number of source and microphone locations. The background levels in the receiver room are measured and the reverberation time in the receiver room is also measured. From the results, the impact sound insulation results (LnT,w) is calculated and compared to the requirements of Approved Document E of Building Regulations.

To help control noise issues APT Sound Testing can undertake UKAS accredited Part E sound testing in London and the South East. Our sound test engineers carry all the latest acoustic equipment. We provide full UKAS accredited sound insulation testing and air testing, so all or testing is completed to a strict quality controlled standard

If you would like advice on your acoustic design or sound testing in London, please contact us now at or call us on 07775623464.

Sound Insulation Testing – Questions & Answers.

 Sound Insulation Testing – Questions & Answers.

APT sound testing often get asked a similar bunch of questions in regards to sound insulation testing. Over the last couple of years we have collated these questions and answers and to help our valued clients we have shown these below.

What is sound testing for Part E
Sound Insulation Testing is a method of quantifying the sound insulation performance of  walls and/or floors. Sound testing can be carried out on party walls, party floors or facades of any building.

What is sound insulation?
Sound insulation is the property of a wall and /or dividing partition to resist the passage of noise.

Why do I need sound testing on my Project/Property?
The largest single reason for disputes between neighbours is noise complaints. Approved Document Part E – Resistance to the passage of sound describes minimum standards to be achieved by newly built domestic dwellings.

What building regulation do we work to?

Approved Document Part E, sets out minimum standards for sound insulation performance to be achieved by party wall and party floors. Building contractors may show compliance with Part E of the Building Regulations by two methods. One method is to register plots to be built with Robust Standard Details Limited and the other is to show as-built performance by Pre-Completion Sound Testing to Part E of Building Regulations.

When are Pre-Completion Sound Tests carried out?
Pre completion Sound testing is carried out when the construction of party walls and floors are largely complete. Windows should be in place with any vents closable. Internal and external doors should be in place, along with skirting, cornicing and plug sockets in place. Sound testing on floors must be carried out before any soft coverings are in place.

 Do detached properties require sound testing for Part E of Building Regulations?

No, only attached properties require sound tests, detached properties share no common partitions with any other properties.

Are internal walls/floor between rooms within a single dwelling sound tested?
No, Laboratory test based performance standards (Rw) exist for certain internal walls and floors, but they are not intended to be verified as-built by on site measurement and therefore sound insulation testing is not a requirement.

How many sound tests are needed on my Project?

Approved Document E states that one set of sound tests is required for every 10 units in a group or sub-group. A group or sub-group is defined where significant differences in construction or layout occur, 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 (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.

How are plots selected for sound testing?
We will usually specify the sound insulation tests that are required. We first look at the plans then work a testing schedule taking into account testing through both the projects lounges & bedrooms where possible. We will also try and undertake testing across walls and floors in different areas of the building. The building control officer, warranty provider or other concerned parties may require you to carry out sound testing in specific areas or plots. However where this has not been stipulated we can advise accordingly. When we have specified the sound testing schedule it should always be checked by building control and/or the client to seek their approval before the commencement of testing.

How do I Preparing my Site for Sound Insulation Testing?

APT always send out a checklist with our fee proposals to help you prepare for the sound testing, as we always want our clients to be fully prepared so they can pass their sound testing at the first attempt.


Will the sound insulation testing disrupt work on site? 
There should be minimal site disruption during the sound insulation testing. However, although high levels of noise are generated but in order to make accurate test measurements, relatively quiet conditions are needed to take accurate measurements. This means that anyone working in the testing area will have to leave temporarily and any noisy works in the vicinity of the test rooms will need to be halted i.e. using power tools.

How long will the sound testing take?

The time taken for London sound testing varies with site conditions, but generally a ‘6 pack’ set of tests on houses and flats takes about one to two hours. Obviously this depends on the site being fully prepared in line with our sound testing checklist.

How do I know if I’m ready for a sound insulation test?
The plots should be at least at second fix stage – for further details please refer to our checklist.

Do I need all internal and external doors and windows installed?
Yes, all internal and external doors must be fitted and operable prior to the sound testing. Trickle vents must also be installed where required.

 What if I only have 110 volt on site?

Unfortunately we cannot undertake the testing; we will need 240V to undertake the sound insulation testing.

Should I inform my neighbours of the impending sound testing?
If the building is attached in any way to occupied properties then you will need to inform the neighbours. To comply with Part E we need to gain access to the neighbouring properties to undertake the sound test. You will need to ensure that access is provided to the neighbouring properties throughout the sound testing.

Can you offer advice to help me to pass my sound insulation testing?
We 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 plans during the design stages of the project, we can check the design to see if there are any junctions or details where ‘noise flanking’ may occur. You can then change your design to lower the chance of a sound test failure.

Do you have a check-list to help us prepare for the sound testing?
Yes, we have an informative checklist to help prepare for the testing, please visit our website at to download the checklist.

Is it easy to upgrade the sound insulation in my Existing Home?.

Yes of course. If excess noise is causing you stress and anxiety, in comparison upgrading the walls/floors to your existing property can be a worthwhile process. its normally quite easy to upgrade walls and floors/ceilings to lower sound transmission. Sometimes it can be as easy as installing an acoustically (insulated) backed board against the offending partition. In all instances it is important not only that the right products are used to cause minimal disruption but they are also fitted correctly in-line with manufacturer’s guidelines. .

Rest Assured

We believe in working with our clients whether they are existing home owners suffering acoustic problems or large developers requiring a more expansive service to achieve sound testing compliance. We believe that by being involved at the beginning of a project we can often save our clients expensive and difficult remedial works at the completion stage of a project.

If you would like more information on our full range of services please contact us now at or call us on 07775 623464


Planning Noise Survey Guidance

This guidance is to assist developers and consultants who are involved in  developments where planning permission is required and noise is a consideration and a noise survey for planning is a planning condition requirement .

At what stage will a noise survey and PPG24 report required?

A noise survey and PPG24 report may be required at the application stage or once planning.

permission has been granted. A noise survey and report are required if:

  • the proposed development with commercial areas that may create noise which may affect nearby noise sensitive properties. For example, a new commercial activity near existing residential properties.
  • the proposed development positioning will be sensitive to noise and is likely to be affected by existing noise sources i.e. busy roads, railway, airports or commercial activity.

What is the PPG24 noise report for?

The PPG24 noise report is to demonstrate that:

  • the source of noise is evaluated and quantified
  • nearby noise sensitive receptors identified
  • noise receptors have been determined with reference to noise standards

The PPG24 noise report (where required) will also set out control measures where it is necessary to reduce noise to acceptable levels. For example, the installation of different glazing e.g. from double to triple glazed panels or acoustic trickle vents are installed so that internal noise standards are met.

sound testing equipment

When should a PPG24 noise report be submitted?

A PPG24 noise survey and report should be submitted during pre-application discussions or

more commonly during a planning application. In some circumstances, a planning condition will be included on the planning permission requiring the submission of a noise report.

As noise surveys are usually carried out prior to completion of a development, compliance with any noise standards are demonstrated by calculation. However, the local authority may also request a post-completion noise survey to prove that noise standards have been achieved.

Who is suitably qualified to carry out noise assessments and provide a noise report?

A noise survey must be carried out by a suitably qualified acoustic consultant. APT Sound Testing is a UKAS accredited company and as such is deemed suitably qualified to undertake noise surveys for planning, we also have vast amount of experience and skill in dealing with PPG24 Noise Surveys for the planning applications for all types of developments throughout the United Kingdom.

If you would like more information on our PPG24 noise assessments or PPG24 Noise Surveys then please contact us at: or visit our website at:



In our experience its often the location and poor dwelling layouts that can cause sound testing failure. plays an important role in relation to the levels of subsequent ambient or background noise that surrounds the occupants. Loud  noise sources such as Roads with high traffic volumes, railway lines or airports or entertainment venues can provide a high level of ambient background noise, which may help to ‘mask’ the perceived noise that is being transmitted between dwellings.

Planning Room layouts and functions

Planning a good acoustically favorable dwelling layout can help to reduce the number of noise problems that will occur and help you pass Part E Sound Testing

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 to the bedroom next door through the dividing partition; this can lead to annoyance and frustration for the neighbor.

If neighbours have varied working patterns the layout and the use of rooms are particularly important. Complaints about noise may more often result when the living room of one dwelling is over a bedroom of another dwelling, for example.

Changes to the external building façade

APT have undertaken many façade sound tests to ISO 140 Part 5, in our experience many of the new buildings are struggling to achieve a rating of 40dB, which makes a mockery of Part E as you need to achieve 43dB and 45dB for sound testing on refurb and new build dwellings. Often simple upgrades such as the replacement of double to triple glazing can reduce the level of external noise (termed background noise) entering the dwelling. As such, there may be less background noise and neighbours may hear each other more easily.


Neighbour Relationships

Often the perceived quality of sound insulation may also be influenced by the relationship with their neighbor. If the relationship is amicable then the noise intrusion and the level of noise may be more acceptable than in situations where there is disagreement or hostility between neighbours. Noise issues may only become apparent when there is a change in the lifestyle or the neighbor adopts new work patterns, or when new neighbours move in. Even if the building has passed their dwelling sound test with good results, people may pick up noise in the early AM if neighbours are returning from their work shift.

New building works

Previous service works for water pipes, drainage and heating systems can influence the overall performance of a wall or floor, i.e. access may be needed the SVP pipes within the pipe boxing. During the works the acoustic lagging may be removed to get to the SVP pipe; unfortunately this may not be replaced after the works are complete. The subsequent sound of rushing water may then be audible. Also during other works ceilings such as lathe and plaster may have been removed and replaced by one layer of 12mm plasterboard, even though this is a new material, it may not have the mass of a 40mm lathe & plaster ceiling resulting in the increase of noise levels from the property above.

Surface material changes (carpet to timber)

In our experience one of the most common triggers for complaints is the change of room surface (e.g. from carpet to laminate flooring) treatments or materials. We have undertaken many sound tests on existing buildings where the occupier has changed from carpet to timber and/or tile. Without the applying the acoustic upgrades for this change in material this can typically lead to a 20dB reduction in insulation performance. This can lead to occupants below this floor changing their assessment of impact noise from “acceptable” to a level they may describe as “unacceptable”.

Past experience

People who have previously lived in detached houses and move into a flat or attached dwelling they may feel that the level of sound insulation is poor, however this may not be the case and the sound tests results may actually be quite good – well in excess of the minimum standards as set out in Part E of Building Regulations.

If you would like more information in regards to our acoustic and sound testing services, please contact us now at or visit our website at:



We at APT often get asked why a design that has passed easily in the laboratory has struggled – and sometimes failed to pass the sound testing for Part E

Despite site contractor’s best endeavours, it is extremely difficult to build to the stringent exacting standards of the test laboratory. When the construction assembly is undertaken in the lab, it has gone through an exacting installation technique prior to the sound test, which is the reason why better sound testing levels are achieved.

Throughout the acoustic installation the manufacturer’s guidance is followed to the letter by the lab technicians. Although, this should be replicated on site, it seldom is and so a design which can be robust and well in excess of Part E requirements can lose 10dB or more compared to the results achieved in the laboratory. Unfortunately there are many reasons why this occurs and it’s usually down poor quality operatives and other on-site other issues such as cost, time and programming constraints come into play.

We have undertaken many sound tests where the acoustic design details showed the partitions should achieve in excess of 50dB, only for it to fail with sound test results below the required 45dB.  This is why a 7-9dB tolerance should be allowed between the dB rating of the acoustic solution and the onsite construction. Unfortunately, if cost constraints come into play and subsequent allowances aren’t made for the onsite acoustic performance there is a high probability it will fail the sound testing, which may lead to expensive remedial works as well as delayed handover which will be far more expensive in the long run.

sound testing

There are many reasons why the onsite construction results are worse than the laboratory,   issues such as such as using the wrong fixings and not installing the insulation to name but two. Either of these can easily lead to a sound test failure.

It is very important that acoustic installation details are closely followed to ensure that the onsite results are as close as possible to the laboratory target. We offer an acoustic design service, to help you achieve Part E compliance at the first attempt.

The following list explains what should be done to achieve a successful sound tests and Part E compliance:

  1. Ensure that the construction team is fully briefed of the acoustic details.
  2. Ensure that the manufactures installation booklet is on site at all times.
  3. Ensure that the Acoustic floor is fitted with staggered joints.
  4. If you are installing floating screed ensure all isolation layer joints are overlapped and taped.
  5. Ensure all the Acoustic floor is sealed watertight even around heating pipes.
  6. Do not nail or screw through an Acoustic Floor.
  7. Do not screws plaster board into joists, when using a Resilient Bar system.
  8. Ensure the insulation fills the whole width of void
  9. Pack around pipe work and double board with staggered joints.
  10. Ensure that the plasterboard on any walls is complete right down to within 5-10mm of the subfloor and seal all gaps.
  11. Ensure you use the isolation tape around the wall of each room.
  12. Ensure plasterboard is fitted with staggered layers and all joints sealed.
  13. If using Resilient Bars ensure that they are fitted as per manufacturer’s recommendations.
  14. Ensure all Fireplaces are blocked up with brick or a twin lined plasterboard system and filled with acoustic insulation.
  15. Ensure that any RSJ’s or supporting steel work is insulated and isolated from plasterboard.
  16. Ensure all waste pipe service runs are boxed in with insulation and plasterboard.
  17. Ensure all doors and windows are installed before the test is carried out, to stop noise transference.

APT offer an acoustic design service to make sure the acoustic elements are being installed as per the manufacturer’s guidelines, if you are worried about passing your sound testing at the first attempt please don’t hesitate to contact us now at: or visit our website at:


Quantifying Sound levels for Sound Testing Failures

Quantifying Sound levels for Sound Testing Failures

APT Sound Testing often ask us about the parameters behind the sound testing under Part E. To try and clarify sound levels in more detail we have written a brief explanation.

What is sound or Noise?

Noise or sound  is often defined as unwanted sound. Sound is defined as any pressure variation heard by the human ear. The sound pressure level (SPL) is a measure of the air vibrations that make up sound. Because the human ear is sensitive to a wide range of pressure levels, the SPL is measured on a logarithmic scale with units of decibels (dB).


How do we  perceive noise or sound?

Healthy human ears perceive pressure variations over a wide range of frequencies — from low as low as 20 Hz to frequencies as high as 20,000 Hz. The human ear’s range starts at the threshold of hearing (0 dB) and ends at the threshold of pain (around 140dB) which would be the same as standing next to a large jet engine.

The human ear is less sensitive to sounds in the low frequencies compared to the higher frequencies. For example, a 50 Hz tone must be at a level of 85 dB in order to be perceived by the human ear as being the same loudness as the higher frequency 1000-Hz tone at a level of 70dB

How do you quantify sound?

As mentioned above, sound levels are usually measured and expressed in decibels (dB). Most environmental noise does not consist of a single frequency, but rather a broad band of frequencies differing in sound level. The intensities of each frequency add to generate sound. The method commonly used to quantify environmental sounds involves evaluating all of the frequencies of a sound according to a weighting system which reflects that human hearing is less sensitive at low frequencies and extremely high frequencies than at the mid-range frequencies. This is called “A” weighting, and the decibel level measured is called the A-weighted sound level (dBA).

Quantifying sound testing failures

As a rule of thumb, a doubling in the loudness of the sound occurs with every increase of 10 dB in sound pressure. In other words, for most individuals a 60 dBA noise would sound twice as loud as a 50 dBA noise.

If a sound testing fails, the client often asks by how much. When we confirm it has failed by 5dB they usually say ‘if that’s the case I only need to improve the partition by 10%’, unfortunately that isn’t the case – the partition has actually failed by 50% subsequently the partition will need major upgrades to pass the sound testing under Part E of Building Regulations.

APT Sound Testing can advise on all types of acoustic design, whether it’s accomplished during initial construction or during a refurbishment/renovation project.  We have the technical experience to help identify and rectify your soundproofing or noise control problem.

If you would like more information in regards to sound testing please follow our blog at: or contact us at: or visit our website at:

What is a Planning Noise Survey

What is a Planning Noise Survey

A planning noise survey needs to be carried out by a suitably qualified acoustic consultant, preferably UKAS accredited in acoustics. APT is UKAS accredited for acoustic surveys and we have vast amount of experience and skill in dealing with BS4142 noise assessments and PPG24 Noise Surveys for the planning applications for both small and large businesses and developments throughout London and the United Kingdom. All you need to do is send us a site plan layout showing the site along with the nearest noise sources such as a main road or railway line. Once received we will send you a quotation for a noise survey – it’s as simple as that!

sound testing

Noise Surveys for New Developments

A noise survey and report should be submitted during the pre-application process and discussions on planning applications. In many circumstances a planning condition will stipulate that a noise survey will need to be undertaken.

Noise surveys are normally carried out prior to completion, however the local authority may also require post a BS 8182 noise level survey to prove that the noise standards have been achieved within the living rooms and bedrooms.

The following information will usually need to be included within the noise survey report.

  1. The reason and scope of the report.
  2. Location plan of the proposed development and likely receptor points such as the nearest residential window/s.
  3. The noise survey Methodology including the noise monitoring location, the equipment used and the weather conditions during the noise survey.
  4. Reasons for deviations from standard methods.
  5. Full table of results.
  6. A comparison of survey results against the noise standards.
  7. Recommendations for noise control measures – acoustic barriers etc.
  8. Full calculations against noise reductions expected to support any suggested noise control measures.

When is a noise survey and PPG24 report required?

A noise survey and PPG24 report may be required at the application stage or once planning

permission has been granted. A noise survey and report are required if:

  • the proposed development with commercial areas that may create noise which may affect nearby noise sensitive properties. For example, a new commercial activity near existing residential properties.
  • the proposed development positioning will be sensitive to noise and is likely to be affected by existing noise sources i.e. busy roads, railway, airports or commercial activity.

What is the noise Survey report for?

The noise survey report is to demonstrate that:

  • the source of noise is evaluated and quantified
  • nearby noise sensitive receptors identified
  • noise receptors have been determined with reference to noise standards

 The noise survey report (where required) will also set out control measures where it is necessary to reduce noise to acceptable levels. For example, the installation of different glazing e.g. from double to triple glazed panels or acoustic trickle vents are installed so that internal noise standards are met.

If you would like more information on BS4142 noise survey or PPG24 noise surveys for your business or development, please contact us at: or visit our website at:  Bye for now APT



One of the most common reasons for partitions failing the sound testing is down to noise flanking between partitions.

Noise Flanking is a term used by acoustic engineers wherein the sound passes over the top or under the primary partition separating the two spaces under test. Flanking sound transmission can be especially bothersome in multi-family residential buildings do to the sheer number of dividing partitions.

One way to reduce the chance of to flanking transmission/s is at the design phase of the dwelling. Unfortunately, by Simply specifying high performance wall and floor partitions between dwelling is no guarantee to a sound isolation and subsequently a successful sound test. APT Sound Testing offer both preconstruction and post construction design solutions to achieve the required sound isolation requirements of Part E of Building Regulations.

This Plate Shows The Main Air Leakage Paths


We also offer an acoustic onsite inspection service to ensure that the sound insulation elements are being installed as per manufactures guild lines and the quality of the workmanship is consistent with ‘best practice’ noise control procedures.

You can also undertake you own checks by asking the design consultant i.e. the architect or the builder what steps have been taken to insure your building will be sound adequately sound proofed from your neighbours and from noise intrusion through perimeter envelope from outside the building, after all there isn’t any point your dwelling having high spec acoustic insulation between the inner partitions if sound is transferring through the outer envelope.

 It is never safe to assume because the architect has specified high performance walls, windows and floor/ceiling assemblies that the materials and onsite workmanship will result in compliance with the anticipated results and ultimately a successful sound test. In all these instances successful sound isolation in your home depends on the workmanship during the sound insulation installation phase, the problem is the site installer may know little about noise control techniques unless he is give the right supervision and direction the construction phase.

Part E of Building Regulations stipulates the minimum standards for noise control between residential dwelling units. Upon completion of the building the Building inspection department will need the sound test certification prior to the issue a certificate of occupancy. This shows that the building meets minimum building code standards including sound isolation.

Typical Flanking Sound Transmission Pathways:

  • Dividing Floors – 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 Ceilings – Above and Through the Ceiling Space (where an adequate acoustic break has not been carried on through the ceiling void)
  • 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)
  • Shared Structural Building Components – Floor Boards, Floor Joists, Continuous Drywall Partitions, Continuous Concrete Floors, and Cement Block Walls.
  • 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)
  • Structural Joints – Perimeter Joints at Wall & Floor, Through Wall & Ceiling Junctures (these should be filled with acoustic mastic)
  • 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 area)
  • Around the End of the Partition Through the Adjacent Wall (acoustic mastic should be used to seal this junction)

Even if you your wall/floor has been designed so it should provide a high acoustic rating exceeding Part E requirements, this may not be enough. Unfortunately, sound will always find the weakest link, for instance construction workers will usually jack the plasterboard tight to the ceiling in order to achieve a nice tight joint at the ceiling. This often leaves a void or potential noise transference point at the floor/wall junction, which will eventually be covered with a piece of thin skirting board. Failure to fill the joint between the wall and the floor with acoustic mastic can reduce even a 50dB rated wall to under 40dB which will fail the minimum standard of 45dB for sound insulation testing as stipulated within the Building Regulations Part E.

This Video Clearly Shows Sound Flanking Through a Wall

Often the sound insulation manufacture will provide test lab results for their material. However, you should usually reduce the acoustic target by 4-5dB due to onsite construction. When the construction assembly is tested in the lab it is also certified and the installation techniques are described in detail.  Unfortunately it is not always possible to replicate the exact conditions on the site compared to the ideal conditions within in a lab setting, which is a far more controlled and scrutinised environment. This is the reason why a 5 point difference is allowed between the construction design on paper and the actual on site performance.

APT Sound Testing can advise on all types of acoustic design, whether it’s accomplished during initial construction or during a refurbishment/renovation project.  We have the technical experience to help identify and rectify your soundproofing or noise control problem.

If you would like more information in regards to sound testing please follow our blog at: or contact us at: or visit our website at: