5.1 Noise separation
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Noise nuisance affecting people who stay in residential buildings such as hotels or care homes has risen over the years as rooms are used for more than just sleeping accommodation. These rooms are now multi-functional, and greater numbers of noise-producing pieces of equipment and appliances such as audio and TV are now used. Noise generated by people in hotel corridors as they move about and bang doors or talk loudly can cause disturbance to those trying to sleep in nearby rooms.
Complaints regarding noisy services are made regularly. 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, and not an issue specifically dealt with here. However guidance is given on special care that should be taken at the decision stage in the choice of service equipment, their 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 non-domestic premises. More information on this is contained in PAN1/2011.
Conversions - in the case of conversions as specified in regulation 4, the building as converted shall meet the requirement of this standard (regulation 12, schedule 6).
Airborne sound insulation should be provided where any separating wall or separating floor is formed between areas in different occupation. For example:
Impact sound insulation should be provided where any separating floor is formed between areas in different occupation. For example:
between rooms intended to be used for sleeping. The lower room should be protected from sound emanating from the upper room
between rooms intended to be used for sleeping and other parts of the same building. The room below should be protected from sound emanating from other parts of the building above
between rooms intended to be used for sleeping and other parts of the same building directly above e.g. common stair or corridor, communal lounge, or car parking garage
a roof, walkway or access deck located directly above rooms intended to be used for sleeping and to which there is access, other than where it meets the conditions of (c) or (d) below.
Impact sound insulation need not be provided for:
a roof above a non-habitable space, such as a roof space
a separating floor between a residential building and any other non-domestic building directly below
a roof, walkway or access deck located directly above rooms intended to be used for sleeping to which there is access for maintenance purposes only
a roof, walkway or access deck located directly above rooms and to which there is access, where it is for the sole use of the residents of the residential building.
The following design performance levels are given for the control of sound through separating walls and separating floors. Although not specifically covering non-domestic buildings, 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:
achieving a high quality of workmanship on site
supervision throughout the construction process
the relationship between separating and adjoining elements (e.g. external walls, roofs and windows) to combat flanking transmission
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 [1]
| Design Performance | New build and conversions not including traditional buildings | Conversions of traditional buildings [2] |
|---|---|---|
| Minimum airborne sound insulation [3] | 56 DnT,w | 53 DnT,w |
| Maximum impact sound transmission [3] | 56 L’nT,w | 58 L’nT,w |
Additional information:
For the definition of DnT,w and L’nT,w see clause 5.0.4.
Notice should be taken of the guidance on conversions in clause 5.1.5.
See clause 5.1.1 for application of these performance levels to separating walls and separating floors.
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 5.1.7 to 5.1.9).
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. As these are designed for domestic types of construction they may not be suitable for use in non-domestic buildings.
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.
5.1.5 Conversions
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.
With older buildings achieving the performance levels in clause 5.1.2 becomes more difficult, therefore the levels for traditional buildings are less demanding than for new build and conversions.
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.
Although not specifically covering non-domestic buildings further advice on providing sound insulation in 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 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.
For larger or more complex work, advice on conversions may be sought from an acoustic specialist who should be able to offer appropriate design guidance.
Building service installations serving common areas in residential 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 building have all been known to be a source of complaint.
Therefore, it is important that the design of building services, their position in the building and the building structure should be considered at an early stage in the design process.
Services passing through separating walls or separating floors must comply with the relevant standards in Section 2: Fire.
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 area 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.
Although not specifically covering non-domestic buildings, 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 effectiveness of a construction to reduce sound transmission depends on several factors; the design, the buildings within which it is formed and the quality of the workmanship.
The use of any of the methods listed in clause 5.1.2 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 [1]
| Design Performance | New build and conversions not including traditional buildings | Conversions of traditional buildings [2] |
|---|---|---|
| Minimum airborne sound insulation [3] | 56 DnT,w | 53 DnT,w |
| Maximum impact sound transmission [3] | 56 L’nT,w | 58 L’nT,w |
Additional information:
For the definition of DnT,w and L’nT,w see clause 5.0.4.
Notice should be taken of the guidance on conversions in clause 5.1.5.
See clause 5.1.1 for application of these performance levels to separating walls and separating floors.
On completion, new buildings and conversions should be tested. At least 1 test should be carried out on each separating wall and separating floor of different construction within the completed buildings, where there is a room intended for sleeping.
Inaccessible areas - there may be some locations where it is not possible to carry out a sound test, as access to an adjoining building may be restricted or prevented. When a conversion of an attached building occurs, for example to a mid terrace building, it may not be possible to gain access to the adjacent building to carry out tests to the separating wall. In such cases, it may not be appropriate to test.
Methods of testing - 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.
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.
Airborne 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.
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 5.1.8 to check that the work achieves the test performance levels.