5.1 Noise separation
Noise nuisance outwith the control of dwelling occupants has increased substantially over the last decade. This is mainly as a result of people’s changing lifestyles, greater numbers and use of sound-producing equipment and household appliances.
There has been a dramatic increase in the use of electrical goods, particularly sound producing equipment such as audio and TV. Music can be more bass orientated and played at higher volumes, whilst speakers mounted on walls may improve the quality to the listener, they can create a disturbance to others. The intention is not to prevent all sound from being heard, but to limit noise nuisance by achieving levels of sound insulation that will help to reduce the effects of sound on people in their home.
Complaints regarding noisy services do occur. Dealing with the varying levels of sound produced by service equipment, such as lifts, heat pumps or air conditioning units in buildings is a complex task. Guidance is given on the care that should be taken at the design stage in the choice of service equipment, installation and location within the building.
Designers should be aware that some Local Authorities may also set noise reduction targets. This is usually enforced through environmental health and planning legislation for noise emanating from commercial premises to dwellings, and more information on this is contained in PAN 1/2011.
between a dwelling and a non-domestic building
between a dwelling and other parts of the same building, e.g. common stair or corridor, communal lounge, or car parking garage.
Airborne sound insulation need not be provided for:
a separating wall dividing any 2 buildings, such as garages, conservatories or porches, or a combination of these, where each building is attached and ancillary to a dwelling
an external wall such as a wall dividing a dwelling from an access deck, since it is not a separating wall
a wall or floor between a dwelling and any accommodation that is ancillary to the same dwelling, such as a garage.
Impact sound insulation should be provided where any separating floor is formed between areas in different occupation. For example:
between a dwelling and a non-domestic building with rooms intended to be used for sleeping
between a dwelling, and other parts of the same building directly above e.g. common stair or corridor, communal lounge, or car parking garage
between a dwelling and a non-domestic building other than where it meets the conditions of (c) below
a roof, walkway or access deck located directly above a dwelling and to which there is access, other than where it meets the conditions of (d) and (e) below.
Impact sound insulation need not be provided for:
a roof above a non-habitable space, such as a roof space
a floor between a dwelling and any accommodation that is ancillary to the dwellings such as a garage
a separating floor between a dwelling and a non-residential non-domestic building directly below
a roof, walkway or access deck located directly above a dwelling and to which there is access for maintenance purposes only
a roof, walkway or access deck located directly above a dwelling and to which there is access, where it is for the sole use of the residents of the dwelling.
The following design performance levels are given for the control of sound through separating walls and separating floors. The levels have been developed from research covering sound and perceived sound in dwellings. They have been identified as levels, based on normal domestic activities that have been shown to produce few noise complaints.
However experience shows that the performance of a construction is dependent upon:
and these factors should be carefully considered at the design stage.
All work should be designed to the levels in the following table:
Table 5.1. Design performance levels in dB 
Two methods are provided on ways to achieve these levels which can lead to meeting the standard. They are by the use of:
Example Constructions (see clause 5.1.3), or
other constructions (see clause 5.1.4).
These methods are to be used in conjunction with the testing arrangements (see clause 5.1.8 to 5.1.10).
A further method of meeting Standard 5.1 rests outwith the Domestic Technical Handbook. This involves using 'Robust Details (Scotland)' - http://www.labss.org/robust-details-limited. If all the scheme rules are followed then post-completion testing (see clauses 5.1.9 and 5.1.10) is not necessary.
Example Constructions have been developed that will repeatedly achieve the design performance levels in the table to clause 5.1.2. They have also been developed from constructions that are in general use in the UK, and that are known to reduce the range of sound frequencies that can generate complaints.
The Example Constructions are available on the BSD website http://www.scotland.gov.uk/topics/built-environment/building/building-standards.
Clause 5.1.3 provides guidance on constructions that have been designed and tested to repeatedly achieve the performance levels in the table to clause 5.1.2. However it may be necessary, preferable or desirable, to include new or innovative constructions into a proposed design.
Where constructions that have not been tested previously are used, the services of an acoustic specialist may be obtained, who should be able to offer design guidance on constructions that are capable of achieving the performance levels in the table to clause 5.1.2.
Achieving the design performance levels for conversions can present challenges to a designer. The presence of hidden voids within constructions, back to back fireplaces, cupboards and gaps between construction elements in walls and floors, mean that it may not be possible to use ‘pattern book’ type constructions to achieve the design performance levels. When conversions are undertaken, the adaption of the existing building should be considered at the design stage. Conversions and conversions of traditional buildings should achieve the performance levels in the table to clause 5.1.2.
The design proposals for the conversion of a traditional building should be considered carefully so that any measures taken will improve the sound insulation. The performance levels in the table to clause 5.1.2 should be considered as a benchmark, but it may not be possible to achieve these levels in all circumstances. Consultation on such matters at an early stage with both the verifier and the planning officer of the relevant authority is advisable.
Historic and Listed buildings will, prior to conversion, display unique characteristics as far as sound insulation is concerned. The original building design and construction will influence the level of sound insulation achievable for the separating walls and separating floors. For this reason, specific prescriptive guidance on such buildings is not appropriate. The relevant authority may, at their discretion, agree measures that respect the character of the building.
Advice on the general principles of sound insulation in Historic and Listed buildings can be obtained from the Building Performance Centre, Napier University booklet 'Housing and Sound Insulation – Improving existing attached dwellings and designing for conversions' http://www.scotland.gov.uk/topics/built-environment/building/building-standards.
The conversion of a roof space into a habitable area, although very common, can present problems as it is unlikely that access to the roof space in the adjoining dwelling can be assured. Where an existing separating wall in a roof space is constructed of a single leaf of masonry only, it would be appropriate to provide one leaf of a free-standing framed construction next to the existing wall as each attic is developed. Example Constructions - detail 3: timber frame twin stud wall; gives a typical arrangement.
The building owner may wish to carry out a pre-conversion sound test prior to the start of any conversion, ideally during the building survey process. The acoustic performance of the existing construction can then be established and problems identified that will allow the design of a tailored acoustic solution to be determined at an early stage.
A door in a separating wall dividing a dwelling from a common area of a building can create an acoustic weak point in the wall allowing unwelcome noise into the dwelling. As entrance doors to dwellings from common areas must comply with the relevant standards in Section 2: Fire, Section 4: Safety and Section 6: Energy the doorset will be relatively robust, and the weakest point for noise to enter the dwelling will be through the gap between the door frame and the door.
Entrance doors to flats and maisonettes located in a separating wall should be fitted with a perimeter seal, including the threshold, to minimise noise transmittance through the doorset.
A compressible type of seal may be used such as a rubber strip. Where the seal is of a type that combines a smoke and noise seal, the product literature should be consulted to confirm the seal will achieve the desired effect. The seal should not interfere with the closing mechanisms of a fire door and provide a positive seal between the door frame and the door.
Building service installations serving common areas in domestic buildings have the potential to cause noise nuisance. For example, common plant such as lifts, air conditioning units, ventilation systems, and drainage pipes running the height of a block of flats have all been known to be a source of complaint.
Service pipes or ducts should not pass through a separating wall, unless they are of small diameter, such as lateral pipework from network risers such as gas, electricity, water and telecom. These pipes or ducts may pass through a separating wall from a common into a single dwelling only.
Custom-built or system chimneys should not be built into timber-framed separating walls. Only masonry chimneys (including precast concrete flue-blocks) may be included as an integral part of a separating wall. However, some thickening of the construction may be necessary to achieve the performance levels in clause 5.1.2.
Only service openings for ducts, service pipework or chimneys may be formed in separating floors. These services should be enclosed above and below the floor with a construction that will maintain the levels of noise reduction recommended for a separating floor in the table to clause 5.1.2.
Service equipment rooms should not be located next to quiet areas such as rooms intended for sleeping. Locating plant in a larger space can help dissipate sound. Also, plant machinery and equipment such as lift rails should be isolated from the walls and floor to reduce vibrations and the resulting sound transmission to rooms intended for sleeping. Vibration from mechanical equipment can be reduced with the use of inertia blocks and resilient mounts.
Structure borne noise is the most common cause of complaints and the most effective approach is to structurally de-couple service installations and mechanical equipment from separating walls and separating floors. Lightweight structures need special consideration and it may be necessary to support noisy plant on a separate, rigid structure. The installation of an independent wall or ceiling lining may help achieve the performance levels in clause 5.1.2.
A report ‘Limit noise transmission to dwellings from services' includes several useful design guide annexes. http://www.scotland.gov.uk/topics/built-environment/building/building-standards. Annex H of BS EN 12354-5: 2009 provides more detailed guidance on the reduction of service noise transmittance through separating walls and separating floors.
Design guides covering low carbon equipment, such as air source heat pumps, contain advice on sound reduction measures and are available at http://www.scotland.gov.uk/topics/built-environment/building/building-standards.
The use of the methods in clauses 5.1.3 or 5.1.4 alone will not guarantee that the performance levels will be achieved. Good workmanship is essential to their performance, and post-completion testing will confirm these levels have been achieved.
Table 5.2. Test levels for Example and other constructions in dB 
On completion, new buildings and conversions should be tested in accordance with the tables in this clause. Note, such testing is not necessary should 'Robust Details (Scotland)' be used, fully adhering to the scheme rules, see clause 5.1.2. This is because 'Robust Details (Scotland)' are designed and constructed to be an average of 5dB better than the test levels in clause 5.1.8 above.
Table 5.3. Recommended minimum number of tests for new build [1, 2]
|Construction Type||No. of attached dwellings||No. of tests for separating walls [houses]||No. of tests for separating walls [flats or maisonettes]||No. of tests for separating floors [flats or maisonettes]|
|New build using Example Constructions||2 - 20||2||2||2|
|21 - 40||3||3||3|
|Over 40||1 extra for every 20 houses, or part thereof||1 extra for every 20 flats or maisonettes, or part thereof||1 extra for every 20 flats or maisonettes, or part thereof|
|New build using other constructions||2 - 10||2||2||2|
|11 - 20||3||3||3|
|21 - 30||4||4||4|
|Over 30||1 extra for every 10 houses, or part thereof||1 extra for every 10 flats or maisonettes, or part thereof||1 extra for every 10 flats or maisonettes, or part thereof|
Table 5.4. Recommended minimum number of tests for conversions [1,2]
|Construction Type||No. of attached dwellings formed by conversion||No. of tests for separating walls [houses]||No. of tests for separating walls [flats or maisonettes]||No. of tests for separating floors [flats or maisonettes]|
|Conversions||1 - 5||2||2||2|
|6 - 10||3||3||3|
|Over 10||1 extra for every 5 dwellings, or part thereof||1 extra for every 5 dwellings, or part thereof||1 extra for every 5 dwellings, or part thereof|
When a conversion of an attached building occurs, for example to a mid terrace dwelling, it may not be possible to gain access to the adjacent dwelling or part of the same building, to carry out tests to the separating wall. In this case, it may not be appropriate to request testing to be carried out. The conversion of a roof space into habitable space, although very common can also present problems. Since it is unlikely that access to the roof space in the adjoining dwelling can be assured it may not be appropriate to test
Sound tests should only be carried out on a building that is complete and when doors, access hatches and windows are fitted. Carpet, should not be used as bonded resilient floor covering or laid before an impact test for separating floors. Sound testing should be carried out in accordance with:
BS EN ISO 140-4: 1998 and BS EN ISO 717-1: 1997, for airborne sound transmission, and
BS EN ISO 140-7: 1998 and BS EN ISO 717-2: 1997, for impact sound transmission.
Airborne sound insulation testing - at least two different loudspeaker positions should be used for the source noise, in accordance with BS EN ISO 140-4: 1998.
Methods using a single source - for each source position, the average sound pressure level in the source and receiving rooms is measured in one-third-octave bands using either fixed microphone positions (and averaging these values on an energy basis), or using a moving microphone.
For the source room measurements, the difference between the average sound pressure levels in adjacent one-third-octave bands should be not more than 6dB. If this condition is not met, the source spectrum should be adjusted and the source room measurement repeated. If the condition is met, the average sound pressure level in the receiving room, and hence a level difference, should be determined.
It is essential that all measurements made in the source and receiving rooms to determine a level difference should be made without moving the sound source or changing the output level of the sound source, once its spectrum has been correctly adjusted (where necessary).
The sound source should now be moved to the next position in the source room and the above procedure repeated to determine another level difference. At least two positions should be used for the source. The level differences obtained from each source position should be arithmetically averaged, D as defined in BS EN ISO 140-4: 1998.
Airbourne and sound impact insulation testing - for both types of testing it is possible to use fixed microphone positions, rotating booms or manual moving microphones (mmm), in accordance with BS EN ISO 140-4: 1998 and BS EN ISO 140-7: 1998.
Doors - it is not normal practise to undertake sound insulation tests where there is a door in a separating wall, such as an entrance door to a flat from a common stair. Allowance should be made if a test is needed for such a separating wall as the door will not achieve the same 'design performance level' as a separating wall, as the door will allow sound transmission through the gaps and affect the sound test results.
Professional expertise - testing should be carried out by persons who can demonstrate relevant, recognised expertise in acoustics for sound insulation testing. This should include membership of a professional organisation which accredits its members as competent to both test and confirm the results.
Noise transmission in buildings is a complex subject and it is difficult to provide definitive guidance on resolving specific problems that have occurred in individual buildings. It may be prudent to seek advice from a specialist who, through experience of sound testing, may be able to identify and resolve any problems.
If the failure is attributed to the construction of the separating and/or associated flanking elements, other rooms that have not been tested may also fail to meet the test performance levels. Additional tests may be needed, over and above the number recommended in clause 5.1.9 to check that the work achieves the test performance levels.