Minimising Noise Flanking Transmission to Pass Sound Tests

Minimising Noise Flanking Transmission to Pass Sound Testing

One way to reduce the chance of noise flanking transmission/s to pass the sound testing for Part E of Building Regulations is to carefully look at the acoustic details at the design phase of the project, as well as good planning and workmanship thereafter. Unfortunately, by simply specifying high performance wall and floor partitions between dwellings is no guarantee to a sound isolation and subsequently successful sound testing.

Sound travels along the path of least resistance between rooms, usually through any penetrations/air leaks or through rigid and poorly isolated connections in the structure itself, these routes are called noise flanking paths.

  • Wide gaps below doors provide a flanking noise pathway.
  • Air leakage around partition walls at the wall/ceilings junction.
  • Sound leaking through ‘lightweight’ hollow-core doors.
  • Through ductwork penetrations between two rooms or boiler cupboards placed back to back.
  • Fixtures & Outlets – Light Switches, Telephone Outlets, and Recessed Lighting Fixtures (if penetrations have been cut back to back with the opposite dwelling under test)
  • Poor sound isolation between floors, if subfloor wooden planking extend beneath the dividing floor partition and into an  adjoining dwelling this will form a sound flanking pathway.
  • Framing connections that include solid framing members passing between building areas such as oak beams where large old houses have ben subdivided.
  • Poor isolation to partition abutments to adjoining walls, ceilings, floors
  • Service penetrations behind back to back kitchens, such as soil stacks, waste and recessed pipework.
  • 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)
  • 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)
  • 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).
  • Recessed light fixtures that pass through the plasterboard and acoustic insulation.
  • The wrong fixings used during the installation of resilient channel systems, i.e. drywall screws that are too long that penetrate into the ceiling joists.
  • Window noise transmission due to poor performance glass etc.
  • Door noise transmission due to the inclusion of lightweight hollow core doors, with large gaps to the bottom of the door threshold.
  • On bathroom partitions, install drywall all the way to the floor before installing the bath and seal all plumbing penetrations through walls with a flexible sealant.


If the wall/floor partitions have poor isolation and can greatly reduce the effectiveness of soundproofing efforts and can lead to sound test failures. Even if your construction allows for ‘robust’ sound insulation ratings, it will be rendered useless, if sound can pass easily through service penetrations in the walls and floors or through lightweight doors.

APT Sound Testing offers both pre & post construction design solutions to achieve the required sound isolation requirements of Part E of Building Regulations.

We offer an acoustic onsite inspection service to ensure that the sound insulation elements are being installed as per manufactures guide lines and the quality of the workmanship is consistent with ‘best practice’ noise control procedures and we have the technical experience to help identify and rectify your soundproofing or noise flanking problem/s.

If you would like more information in regards to sound testing, please contact us at: or call us direct on 07775623464

Should I inform my Neighbours of the Sound Testing?

Should I inform my Neighbours of the Sound Testing?

Your neighbours will need to be contacted if access is required to their properties to complete the sound testing. Also as the sound levels produced during the test are very high it would be ‘neighbourly’ to inform the residents as they are likely to hear the test. If your project is a new build and/or a change of use and its built onto an existing property then chances are you will be required to undertake an airborne wall test. We recommend that you check this with your local building control officer prior to the testing so you can plan access to the neighbouring properties accordingly.
Can I Observe the Sound Testing?

sound testing equipment

APT Sound Testing will happily give you a brief demonstration and overview of the test, if so required; however, during the actual sound testing, we will need to follow stringent rules which restrict extra personnel within the test areas.
I want peace of mind that I’ll pass the sound testing

Poor Sound test results can occur for many reasons. The most common factor influencing acoustic performance is poor workmanship. Detailing is critical to maximising on site acoustic performance, especially in floor and wall isolation and appropriate party wall and floor construction. If inadequate provision for the isolation of materials is not undertaken

Should I inform my Neighbours of the Sound Testing? 

The Correct Site Conditions for Sound Testing

 The Correct Site Conditions for Sound Testing 

To undertake accurate sound testing, we require the site noise levels to be kept to a minimum. During the sound insulation testing, our equipment produces high levels of noise – between 100-110dB! However, to record accurate test measurements, relatively quiet conditions are required on site throughout the testing. Any site operatives working in the testing area will have to leave temporarily and any noisy works in the vicinity of the test areas including external site activity such as groundworks, drilling and banging will need to be halted. 

We also require full access to all the rooms being tested. We provide a full testing schedule within our quotation which will clearly identify suitable couplings of test rooms which may require access to adjoining neighbours dwellings to enable us to complete the sound testing

APT Sound Testing will try to schedule the sound testing with you at a time when noise can be controlled to achieve the best possible testing results. 

sound testing

What’s the Duration of the Sound Testing? 

The time taken to undertake sound testing varies from project to project as no site is exactly the same. Taking into account standard site conditions a set of tests on houses -two airborne walls will take one to two hours. A six pack of tests on flats – 2 airborne walls, two airborne floors and two impact tests will take between two to three hours. Throughout the sound testing, we will require full free uninterrupted access to the units/rooms in all test areas. 

If you require more information on sound testing, please contact us now at or phone me direct on 07775623464.

Our Pathway to Successful Sound Testing

Our Pathway to Successful Sound Testing

Sound Insulation Site Audits

We can undertake acoustic site audits, to let us view the existing site construction. This allows us to check for potential problematic areas such as the inclusion of lightweight blocks within the existing wall construction. It also lets us check that the installation teams are installing the acoustic materials as per manufacturer’s guidelines, thus avoiding crucial onsite mistakes. In our experience a sound test failure is often due to the poor workmanship rather than the actual design. The site survey visits negate the risk of sound test failure.

We can also undertake sample sound insulation 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 which takes into account the performance of the existing construction.

 Acoustic Design Advice

Acoustic Defect Diagnosis & Remedial Advice

With many years’ experience in building acoustics, we are able to diagnose the reasons for the sound test failure and recommend a cost-effective solution. Often, the reasons for the partition failure are obvious to the test engineer in which case the advice will be minimal and subsequently the cost for acoustic design advice will be minimal. Sometimes, there are more technical issues which require more detailed diagnosis and invasive investigation, such as large amounts of noise flanking due to serious design faults, e.g. poor material isolation.

Precompletion Sound Testing

To help enforce good acoustic design principles pre-completion sound testing was introduced July 2003, this resulted in all new build properties and conversions which were built after this date are require 10% of each party wall/floor construction type to be tested.

Precompletion Sound Testing is carried out between pairs of rooms separated by party walls or floors. The two ‘habitable’ areas that usually require sound testing are living rooms and bedrooms, although other rooms can be tested if this is not possible, i.e. kitchen to bedroom.

sound testing equipment

If you need sound insulation testing and acoustic design, please don’t hesitate to contact us at  or call me on 07775623464



Many of our new clients ask ‘ how can we improve our sound insulation on our London Refurbishment projects’. One of the main problems is that a large number of the dwellings in London, consist of flats converted from large Victorian houses. Unfortunately at the time of the building conversion, designing for sound insulation was not a high priority and so many of the dwellings suffer from adverse noise transference between the floor and wall partitions. This can be extremely stressful to the occupant’s well being is a major cause for concern.

There are ways to improve the airborne and impact performance by improving the wall/floor partitions ability to reduce the amount of sound transmission from one side of a construction element to the other. By isolating the different materials may not be enough its own and you may need to improve the mass of the partition as well.

Video Showing Main Noise Transference Points Through Existing Partitions.

Improving Existing Floor Partitions

In our experience of undertaking hundreds of sound insulation tests in London, refurbishment projects usually achieve 30-35dB for airborne sound and 70dB for Impact Sound, if the existing construction has not been acoustically upgraded. These figures do not meet the required 43dB & 64dB as stipulated in Part E of Building Regulations. As sound double every 10dB this is a massive failure and acoustic improvements must be made. Many existing construction consist of a similar construction as shown in as detail 1 below.

Detail 1: Existing Floor Partitions Rated At Approx. 30dB


Acoustic Improvements to Existing Floor Partitions

To reduce airborne and impact sound transmission this usually means adding density and isolation to the floor construction. This can be as simple as adding a drop ceiling consisting of 125mm timber frame. The top of the frame must be a minimum of 25mm below the existing ceiling finish – such as lathe and plaster. Then, to the inside of the timber frame add 100mm of Acoustic Wool and two layers of sound-board tacked to the bottom of the timber frame – all boards to be lapped. This should improve your sound test results by approx. 10-15dB depending on the existing site conditions and quality of the installation. Detail 2 shows this in more detail.

Detail 2: Acoustic Flooring Partition Upgrade


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

The Method for Sound Insulation Testing

The Method for Sound Insulation Testing

The method for testing for airborne and impact sound insulation testing methods is clearly presented in BS EN ISO 140-parts 4 & 7: 1998. The sound insulation rating methods that follow are defined in:


The single figure rating method that gives the airborne sound insulation performance between two adjacent rooms within a building as measured within site conditions. The result achieved is affected not only by the separating element also by the surrounding structure and junction details.

 Rating Method – Ctr

The Ctr adaptation term is a correction that can be added to either the RW (laboratory) or DnTw (site) airborne rating. The Ctr term is used because it targets the low frequency performance of a building element and in particular the performance achieved in the 100 – 315 Hz frequency range. This term was originally developed to describe how a building element would perform if subject to excessive low frequency sound sources, such as traffic and railway noise. This rating is expressed as RW + Ctr and allows the acoustic designer to critically compare performances. The rating method has not been universally welcomed.


This single figure rating method is the rating used for laboratory airborne sound insulation tests. The figure indicates the amount of sound energy being stopped by a separating building element when tested in isolation in the absence of any flanking paths.

Rating Method – Lnw

This single figure rating method is the rating used forclaboratory impact sound insulation tests on separating floors. The figure indicates the amount of sound energy being transmitted through the floor tested in isolation, in the absence of any flanking paths. With impact sound insulation, the lower the figure the better the performance.

Rating Method – LnTw

The single figure rating method that is used for impact sound insulation tests for floors. The figure indicates the sound insulation performance between two adjacent rooms within a building as measured on site. The result achieved is affected not only by the separating floor but also by the surrounding structure, e.g. flanking walls and associated junction details.

 Rating Method – Dncw

The single figure laboratory rating method, which is used for evaluating the airborne sound insulation performance of suspended ceilings. Laboratory tests simulate the room-to-room performance of the suspended ceiling when a partition is built up to the underside of the ceiling with sound transmitted via the plenum.

sound testing equipment

APT Sound Testing is UKAS accredited to undertake both Sound Insulation Testing and is also accredited to ISO 17025:2005 ‘General requirements for the competence of testing and calibration laboratories’. If you would like more information in regards to sound insulation testing and/or acoustic design, please contact us now at: or call us on 07775623464

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.

Sound Insulation & Noise Flanking

Sound Insulation & Noise Flanking

Sound insulation & noise flanking describes the reduction of sound that passes between two spaces separated by a dividing element, such as a wall or floor partition. The sound energy passes through the dividing element (direct transmission) and through the surrounding structure (indirect or flanking transmission). The  noise reduction attributed to the sound insulation is realised via sound insulation testing.

 When the building’s acoustic design is taken into consideration, it is important to consider both methods of transmission. The dividing walls or floors, which flank/abut the dividing element/s, usually constitute the main paths for flanking transmission, but this can also occur at ventilation ducts, doorways, windows etc. If windows are positioned very close to the dividing partition then noise flanking will usually occur around the main building envelope, thus rendering your ‘high spec’ acoustic solution useless.

sound testing equipment

It is extremely unlikely that figures quoted from ‘laboratory sample’ sound test conditions will be achieved on site, as the laboratory installation is described in detail and followed to the letter. However, due to time constraints etc. it is not always possible to replicate the same conditions on a construction site, which is the reason why a 5dB point difference is allowed between the laboratory and construction site sound insulation performance.

Noise Flanking Paths

Flanking sound is defined as sound from a source room that is not transmitted via the separating building element e.g. the wall or floor partition. The sound is transmitted indirectly via paths such as external walls, windows, doors and internal corridors.


If you would like more information on sound insulation testing and/or acoustic design service, please contact us at or call us on 07775623464

Excess Noise Between Dwellings

The Reasons for Excess Noise Between Dwellings

There are a variety of reasons why sound insulation may need to be improved. Some of the typical reasons given by occupants, property managers and developers are:

  • Poor workmanship at the time of construction has led to poor sound insulation and noise flanking due to bridging the acoustic elements via incorrect fixings etc. and its damaged the original components.
  • A change in material of wall or floor finishes (e.g. carpet to laminate flooring), has increased the level of noise transmitted to the dwelling below – this is one of the most common reasons and increase in noise.
  • Changes have been made to the existing construction which has had a negative impact on the sound insulation
  • The original existing construction was never suitable to meet the insulation standards required of a separating wall or floor structure – in-line with Part E of Building Regulations.
  • The existing wall or floor components have deteriorated over time and are in need of replacement this may be because the wrong fixings have been used on the existing floors.
  • The upgrading of the existing windows to double and/or triple glazing has reduced external or background noise through the building façade, thus making neighbour noise more noticeable through separating walls and floors.
  • New cut outs in the existing wall to hide new cable for the wall mounted LCD TV’s is another popular reason for noise bridging through walls.

Other factors may have an impact on the overall noise levels, such as when new neighbours move in. Occupants may be more aware of sound insulation issues due to different living patterns between neighbours.

Upgrades or changes to the buildings structure, i.e. previous service works for water pipes, drainage and heating systems may have removed acoustic materials or interfered with acoustic isolation. This can lead to a wide disparity in performance between damaged and undamaged floors or walls.

In our experience, one of the most common triggers for noise complaints is the change of a room surface e.g. from carpet to wooden laminate flooring or floor tiles.  This can typically lead to a 10-20dB reduction in insulation performance. This can lead to neighbours below the apartment changing their assessment of impact noise from “acceptable” to “intolerable”. This can often lead to protracted and expensive legal issues especially if your lease doesn’t allow for hard surface upgrades.


People who live in detached houses or well-insulated attached houses may never have experienced hearing noise from neighbours, so when they move into a flat or attached dwelling they may feel that the level of sound insulation is poor, when infact it complies with Building Regulations Part E.

If you suspect that your noise levels are too high and you would like us to undertake sample sound insulation testing, or you would like us to investigate your noise complaints, please contact us now at:  or phone us on 07775623464

Sound Testing In House Conversions

Sound Testing Results in House Conversions.

 Due to the housing shortage many houses are being converted into flats, which has resulted in a massive spike in noise complains amongst neighbours in such developments. Much of this rise in complaints are due to insufficient acoustic design at the start of the project, this means the dividing partitions are not being designed or constructed to comply with Part E of Building Regulations for Conversions.

 In our experience many of the sound insulation tests we undertake on refurbishment projects achieve 30-35dB for airborne sound, which is well below the required 43dB as stipulated in Part E. For impact sound testing, the figures are usually around 70dB which is well above the required 64dB, which is also a massive failure.

 Taking the above into account is it essential that the acoustic design is addressed right from the start of the refurbishment project.  The usual existing construction is 175mm joists with floorboards attached to the top and a single layer of plasterboard – as per the below detail:


Upgrades or changes to the buildings structure, i.e. previous service works for water pipes, drainage and heating systems may have removed acoustic materials or interfered with acoustic isolation. This can lead to a wide disparity in performance between damaged and undamaged floors or walls.

 To overcome many of these issues we can visit site and undertake sample sound insulation testing through your property to establish the current noise levels. Once the noise levels have been established we can advise on acoustic upgrades to help you improve the sound insulation levels. it may be as simple as the installation of an acoustic resilient layer on the floor, or a minor wall upgrade.