If you understand the above elements that make up party wall design and construction, you’ll have a more educated eye on the acoustic design of your project. view your problem room. In a nutshell, we are trying to prevent vibrations from crossing the wall partition.
When it comes to soundproofing walls and ceilings, we cannot understand the importance of adding mass. However simply adding mass is not often enough, you also need to consider two important factors:
That of what type of material to use.
where the material should be installed within the wall construction.
when adding mass to walls in buildings one the most common ways is to add cement board or soundboard. This adds mass and makes the walls as heavy and thick as possible. Adding mass to walls is one of the easiest ways to decrease sound vibration, although will not reduce deep bass sounds from being heard.
Another good reason for adding mass to any room is a good way to provide extra insulation, which in turn makes the room more energy-efficient and environmentally friendly.
How do I work out the required mass?
Working out the required mass for the wall to pass the sound insulation test can be quite difficult. For instance, the acoustic rating of a typical masonry wall increases from 45 dB to 50 dB when the thickness is increased from 100 mm (block laid on edge) to 215 mm (block laid flat).
This doubling of mass does not need to be achieved by doubling the thickness of a wall, as you can greatly increase the mass by opting for masonry that has a minimum mass of 1900kg/m3 or (190/m2) whereas many lightweight blocks such as thermalite are only 500kg/m3 (50kg/m2), which can easily lead to sound test failure if used in the wrong situation such as the inner envelope construction and or a single skin construction for party walls.
It’s worth remembering for sound to conduct through a wall, it has to actually move or vibrate the party wall ever so slightly. A heavy mass wall is always much harder to move than a lighter wall. It is very important to note that a heavy wall will still vibrate, just not as easy as the lighter one, with this in mind we then need to use the 2nd element of soundproofing design which is the Decoupling of materials – this is covered in our next article here.
Sound Testing needs to be carried out between pairs of rooms separated by party walls or floors. In most cases, the rooms to be sound tested will be the two main habitable rooms – living rooms and bedrooms. All new build dwellings and conversions that were built after this 2004 are required to have 10% of each party wall/floor construction type to be tested.
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. The three types of Sound Tests usually required – depending on the project configuration) are:
Airborne Wall Tests
Airborne wall sound tests may be required between separate dwellings where a lounge and/or bedroom are positioned against the dividing wall partition. The sound tests are 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.
Airborne Floor Tests
For vertically separated dwellings, airborne floor sound testing may be required, where a lounge and/or bedroom sit’s against the dividing floor partition above and/or below a ‘habitable’ room. The sound tests are 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.
Impact Sound Tests
For vertically separated rooms, an Impact sound testmay also be required. This sound test is undertaken using a “tapping machine”, (as above) 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 (L’nT,w) is calculated and compared to the requirements of Approved Document E.
Non-Residential Sound Testing
It is worth noting that sound insulation testing may also be required in non-residential buildings such as schools, hospitals, workplaces, whereas built performance needs to be demonstrated to ensure noise-sensitive areas (e.g. classrooms, wards, meeting rooms) are suitably insulated from noisier areas or to comply with BB93 & BREEAM requirements.
Sample Sound Testing
If you have an existing building that you are about to convert into flats etc. and need to establish the acoustic performance of the existing partitions, we can undertake sample sound testing on walls and floors to check the sound insulation performance. Thereafter we can forward a targeted acoustic design to comply with Part E of Building Regulations, as well as undertaking the final pre-completion sound testing.
All APT’s test engineers carry the latest Norsonic equipment, which are class one rating all of our acoustic testing/sound testing is completed to a strict quality controlled standard. We provide full ISO & UKAS compliant sound testing.
If you would like more information in regards to your air and sound testing please contact us now at info@aptsoundtesting.co.uk or call us on 07775 623464
Designing Buildings to Pass Sound Testing From the very start of the design phase of a new building, it’s extremely important that careful consideration is given to the acoustic element of the building.
By getting APT involved at the start of the design process we can undertake comprehensive acoustic design reviews and ongoing site surveys. We always advocate meeting with the design team at the earliest opportunity to go through all acoustic elements for the building’s design, taking into account the site constraints and the most cost-effective method of achieving Part E of Building Regulations. We try to forward any possible ‘onsite’ construction problems and difficulties in achieving successful acoustic construction and subsequently the sound testing for Part E.
Designing Buildings to Pass Sound Testing Once we have completed the acoustic design review our services don’t finish there. We provide the site team with ongoing design support and site visits. You will have direct contact with the allocated acoustician from the start of the process through to the successful completion of the project.
Once the first phase of the building is completed, we can undertake sample sound testing to ensure the acoustic design and onsite construction methods are sufficient to pass Part E sound testing.
When it comes to refurbishment projects i.e. houses converted into flats and/or an office block into flats we can undertake a sample test of the existing wall and floor construction. Once we have established the sound levels for the existing construction we can then look at the extent of the acoustic upgrades to attain Part E Complaisance. This is much more effective than just forwarding an acoustic design that may be too excessive and expensive when the existing construction is already ‘acoustically’ robust and therefore only needs to improve by a few dB.
One problem we often encounter (without our design input) is that the building marginally fails during the sound test. The potential problem that is often overlooked is that many types of acoustic design/materials have attained an acoustic rating within a laboratory. It is very difficult and extremely unlikely that the sound levels achieved on a construction site will be as good as in the confines of a stringent laboratory environment.
When the construction assembly is tested in the lab, it is also certified and an exact description of the materials and the installation techniques are described in detail and followed to the letter, obviously, this should be replicated on your site as closely as possible, however, this seldom happens. This is one of the reasons why a 5dB point difference is allowed between the construction design on paper and the actual on-site construction performance. When you consider that sound doubles every 10dB, then 5dB can make a huge difference to the overall performance of the dividing partition under test. If consideration is not allowed during the design process then there will be a greater chance of a sound test failure on your project.
Another potentially problematic area of sound transference and potential sound test failures is down to flanking sound. Noise flanking is when travels along a continuous path due to insufficient isolation/break within the building wall & floor elements. One of the most common flanking paths is along with the inner leaf of an external cavity wall. This may be due to lightweight block construction resulting insufficient mass to prevent noise transference.
Unwanted noise travelling along flanking paths makes the building structure vibrate and this causes the sound to radiate into your room. One solution is to build another wall or ceiling in front of the original, but not connected to it (often called an independent wall or ceiling). APT can help to locate the flanking sound and propose a cost-effective design that will pass the sound testing and satisfy Part E of Building Regulations.
For the smaller projects, we undertake a more simplified acoustic design service consisting of a review of the design drawings, such as floor plans and sections. This usually takes place straight after planning has been approved as increased cost savings can be realised at the earliest stage. We can also undertake sample sound testing if the client is not sure of the existing onsite construction.
We can then evaluate the building design to ensure that it the walls and floors are capable of meeting the acoustic requirements of Approved Document E.
Some of the main areas we consider are:
• There are no potential flanking points, where isolated partitions are wrongly mechanically fixed together to caused noise bridging or the wrong materials have been specified such as lightweight blocks etc.
• The acoustic treatments for Soil Pipes, Stair Cases Steel Beams, etc. to ensure they are acoustically fit for purpose, as these are some of the many areas that get missed.
• Acoustic floor treatments are compatible with the proposed floor finishes i.e. Carpets, Laminates, Floor Tiles and under-floor heating systems.
• The Lighting specification to, ensure they are acoustically compliant to the overall design i.e. down lighter design etc.
If you would like more information in regards to sound testing please contact us on 01525 303 905, email us at: info@aptsoundtesting.co.uk or visit the APT Sound Testing website.
Robust Acoustic Design to Pass Sound Testing in Conversion Projects It is essential that acoustic design is carefully thought out at the start of every conversion project to avoid sound test failures. Throughout the 1980s, most timber frame separating floors involved the following standard construction details:
Floorboards (18–22mm thick)
Gypsum-based board
Mineral wool batt (80kg/m3)
Sub decking
220mm joists
100mm quilt insulation between the joists
One/Two layers of gypsum-based board for the ceiling
Using the combination of floorboard, gypsum board, and mineral wool batt is termed a “platform floor”. There is a wide range of batt densities. If the density is too low the floor surface is able to ‘bounce’ and deflect much more easily. If the density is too high then the floor may be too hard and impact sound is able to transmit more easily to the residential dwelling below.
Sound Testing in Conversion Projects Even when resilient battens are used, continuous structural contact along the joist between the floor sub-deck and ceiling provides a strong path for sound transmission. If contact between the ceiling and the joists can be reduced, an increase in airborne and impact performance will be achieved.
One solution is to add another ceiling element to the overall construction. This can provide the extra isolation required to pass the sound testing in London. This can be achieved by incorporate resilient metal bars which are connected to the underside of the joists and mounted perpendicular (90˚) to the joist direction. If plasterboard has already been tacked to the underside of the joists you can firstly add timber batten and then add the resilient bars, also mounted perpendicular (90˚ to the batten.
Squeaking Floors One common problem is that the Joists are often spaced too far apart can result in a reduction in floor stiffness and complaints about footstep noise at low frequencies. Over-notching of joists can also lead to a reduction in floor stiffness and also potential squeaking. This can result in successful airborne and impact sound tests, however, it won’t stop the squeaking of the floors under the extra load imposed by people walking above.
To help with impact sound testing, timber floors often pass as the separating floors normally have a resilient floor surface or “timber floating floor”. This not only assists impact sound insulation (against footstep noise transference) but also reduces airborne sound transference.
Timber floating floors must use a flanking strip to isolate the floorboards from the perimeter walls and skirtings. If flanking strips are not fitted then footstep noise can easily enter the structure via walls etc. and flank into the adjacent dwellings. In the 1980s, mineral wool was used as a flanking strip but it was difficult to turn round at the floorboard edge. It was also prone to deterioration due to compression and movement under dynamic load. As a direct result of this, 5–10mm polyethylene flanking strips were incorporated into the acoustic design and construction., They are also easier to install and do not degrade over time to the same extent.
There are many reasons why floors may fail the sound testing, such as the use of incorrect mechanical fixing can reduce the insulation performance provided by floating floor treatments and resilient ceiling bars. Using very long screws will lead to the bridging of the resilient layers and noise flanking. Inserting pipes or services within a platform floor can reduce the potential acoustic performance if they are not adequately boxed. Placing pipes or cables under resilient battens can also bridge the resilient layer.
Potential problems with timber frame separating floors
Incorrect bridging of resilient layer by over-long screws/nails
Fixings connecting ceiling boards to resilient bars should not bridge to joists
Extra wide joist spacing that reduces floor stiffness
Platform floor resilient layers damaged by inserting pipes and services within the layers
Reduction in stiffness due to use of joist hangers
Ceiling boards not staggered
Over-notching of joists for services reduces floor stiffness
Incorrect omission of flanking strips at floor edge perimeters.
Whilst it is normal practice to have a building surveyed for its structural integrity, however often the acoustic conditions of a building are not considered until the project is well advanced and the partitions are already built. In some cases, the acoustic performance of the building may not have been considered until the work is complete and the verifier requests a sound test to demonstrate compliance with the Building Standards. If it is found that the separating wall or floor does not comply you may need to action the following:
Extensive remedial works may be required to the wall/floor partitions.
The sound test completion certificate may not be accepted by the verifier
There may be considerable delays to entry for occupants and subsequent accommodation costs.
Pre-conversion sound tests can both avert the risk of non-compliance and avoid damage to the existing fabric.
Potential Problems with Services
It’s very common to run services such as electricity cables as well as water and gas pipes within the floor void. This is acceptable and should not require any additional acoustic attenuation measures. However, care should be taken to ensure that their installation does not damage the deafening material or resilient layers, which is a common cause of sound test failures.
It is strongly recommended not to run waste or rainwater pipes horizontally within a party floor. The pipes can then be boxed properly using insulation rapping and soundboard boxing.
Steel columns can be a source of flanking transmission, in particular hollow steel columns. They can also provide a strong path for structural impact transmission. Pre-conversion sound tests should be able to identify whether any columns act as a significant transmission path and whether any treatment is required. It may not be necessary to treat the column in all dwellings if flanking is limited, however, in many instances, the columns will need to be acoustically boxed to prevent sound test failure. One such treatment for columns would be to construct a free-standing metal stud partition around the column, incorporating 50mm insulation quilt and sheeted with two layers of gypsum-based board. Where columns pass through separating floors, as in old bonded warehouses, the junction between column and floor should be well sealed not only for sound insulation but also for fire. The column linings should be double lined with gypsum-based board (minimum mass per unit area 10kg/m2).
Timber beams do not significantly affect the sound insulation performance of a separating floor. However, if a beam has been installed for strengthening, the boxing around the beam may be a single sheet of lightweight board and may be fixed directly to the beam as this will result in a weak area for airborne sound insulation. This can be resolved by stripping off the boxing, packing any voids with dense mineral wool batt and re-sheeting with two layers of dense gypsum-based soundboard.
Contact APT Sound Testing We hope the above information helps you to understand the potential problems with acoustic design and pre-completion sound testing on your development. If you have a project that needs acoustic design advice or sound testing in London, then please visit our Sound Testing website or phone us directly on 07775623464.
The Different Types of Sound Testing Sound Insulation Testing needs to be carried out between pairs of rooms separated by party walls or floors. In most cases, the rooms to be sound tested will be the two main habitable rooms – living rooms and bedrooms. The sound testing 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.
Sound Testing for Part E of Building Regulations has been a mandatory requirement since July 2003. All new build dwellings and conversions that were built after this date require 10% of each party wall/floor construction type to be tested.
There are two mains types of sound tests that need to be carried out prior to the building handover, they are:
Airborne Sound Tests Airborne sound tests are usually required between horizontally and vertically separated pairs of rooms. The sound tests are 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 new build projects, you are required to achieve 45dB for airborne sound testing through walls and floors and 62dB for Impact sound testing for floors. For refurbishment projects this changes to 43dB for airborne and 64dB for impact.
Impact Sound Tests For vertically separated rooms, an Impact sound test may also be required. This sound test is undertaken using a “tapping machine”, (as above) 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 (L’nT,w) is calculated and compared to the requirements of Approved Document E.
Airborne Sound Testing of Building Facades For the sound testing of external facades, we place the loudspeaker outside the building at a distance of 5m from the facade with the angle of sound incidence equal to 45° ± 5° and such that the real traffic noise impact is simulated the best possible way. The speaker and amplifier are used to generate a steady random noise signal via the loudspeaker source. The sound pressure levels are then measured at 2m in front of the facade plane and 1.5m above the ground.
All APT’s test engineers carry the latest Norsonic sound testing equipment, which is class one rating. All of our sound Testing is completed to a strict quality-controlled standard. We provide full ISO & UKAS compliant sound testing.
If you would like more information in regards to sound testing please contact us at 01525 303905 or visit the APT Sound Testing website today.
