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Hea 05 Acoustic performance

(all buildings)

Number of credits availableMinimum standards

Building type dependent

No

Aim

To ensure the building's acoustic performance, including sound insulation meets the appropriate standards for its purpose.

Assessment criteria

This issue is split into two parts:

The following is required to demonstrate compliance:

Prerequisite

1 A suitably qualified acoustician (SQASuitably qualified acoustician) (see Relevant definitions) is appointed by the client at the appropriate stage in the procurement process (but no later than completion of outline design) to provide early design advice on:
1.aExternal sources of noise impacting the chosen site
1.bSite layout and zoning of the building for good acoustics
1.cAcoustic requirements for users with special hearing and communication needs
1.dAcoustic treatment of different zones and façades.

Acoustic performance standards for all building types except residential buildings and long-term stay residential institutions

One credit - indoor ambient noise and sound insulation

2 All unoccupied spaces comply with the indoor ambient noise level targets as detailed in the more rigorous of criteria 2.a or 2.b:
2.aIndoor ambient noise level targets within national building regulations or other appropriate good practice standards
2.bWhere national building regulations or good practice standards do not exist for the building type or do not provide indoor ambient noise targets, the indoor ambient noise levels comply with 'good practice' criteria levels outlined in Table 20
3 A SQA carries out ambient noise measurements to ensure that the relevant spaces achieve the required levels. Where the measurements identify that spaces do not meet the standards, remedial works are carried out and the measurements repeated to confirm that the levels are achieved prior to handover and occupation.
4 The sound insulation between acoustically sensitive rooms and other occupied areas comply with the privacy index, as detailed in the more rigorous of criteria 4.a or 4.b:
4.aSound insulation between acoustically sensitive rooms and other occupied areas comply with targets within national regulations or other appropriate good practice standards
4.bWhere relevant national regulations or good practice standards do not exist for the building type or do not provide sound insulation performance targets, the sound insulation between acoustically sensitive rooms and other occupied areas complies with the following privacy index: Dw + LAeqT > 75. Where privacy is viewed to be critical by the client or design team (e.g. doctor's consulting room, consulting room within a bank) or where the room is adjacent to a noisy space such as a music room, the area should comply with an enhanced privacy index: Dw + LAeqT > 85.
5 The source and receive room sound pressure levels from which Dw is determined are measured in accordance with (EN) ISO 140-4:1998 and rated in accordance with (EN) ISO 717-1:1996. Measurements must be based on finished, but unfurnished rooms, accounting for, and to include the effect of, any carpets and acoustically absorbent ceilings specified.

Education buildings only

6 Teaching and learning spaces with lightweight roofs and roof glazing demonstrate that the reverberant sound pressure levels in these rooms are not more than 25 dB above the appropriate limits given in Table 20

One credit - reverberation times

7 Rooms or areas used for speech (including meeting rooms and rooms for public speaking) or rooms used for music performance and rehearsal, achieve reverberation times as detailed in the more rigorous of criteria 7.a or 7.b and 7.c:
7.aDemonstrate that the reverberation time or equivalent absorption area for relevant spaces complies with targets within relevant national regulations or other appropriate good practice standards
7.bWhere relevant national regulations or good practice standards do not require the control of reverberation time, achieve reverberation times compliant with Table 21
7.cIn addition, if relevant to the assessed building, all areas used for teaching, training and educational purposes achieve reverberation times compliant with Table 22

Up to four credits - Acoustic performance standards for residential buildings and long term stay residential institutions

8 The building meets the acoustic performance standards and testing requirements as detailed in the more rigorous of EITHER:
8.aAirborne and impact sound insulation values comply with the performance improvement standards, as compared to the relevant national regulations outlined in Table 23
8.bAirborne and impact sound insulation levels comply with the performance standards outlined in Table 24 unless otherwise stated within these criteria.
9 A programme of pre-completion testing is carried out by a compliant test body EITHER:
9.aBased on the normal programme of testing described in the relevant national regulations for every group or sub-group of rooms for residential purposes; this must demonstrate that the performance standards detailed within this issue are achieved OR
9.bWhere there are no relevant national regulations in place, or they require laboratory measurements to demonstrate compliance, the programme of on site pre-completion testing must be carried out based on the 'Frequency of testing required' guidance (see calculation procedures in Methodology) for every group or sub-group of rooms.
10 The number of credits awarded will depend on improvement to the national regulations determined according to Table 23 or Table 24. Where commercial space is below the residential space, only airborne sound insulation tests will be required.

Checklists and tables

Table 20: A selection of good practice indoor ambient noise level targets in unoccupied spaces

Function of area

Indoor ambient noise level*

General spaces (staffrooms, restrooms)

40 dB LAeqT

Single occupancy offices 40 dB LAeqT
Multiple occupancy offices 40-50 dB LAeqT
Meeting rooms35-40 dB LAeqT
Receptions40-50 dB LAeqT
Spaces designed for speech, e.g. teaching, seminar or lecture rooms 35 dB LAeqT
Concert hall, theatre or auditoria 30 dB LAeqT
Informal café or canteen areas 50 dB LAeqT
Catering kitchens 50 dB LAeqT
Restaurant areas40-55 dB LAeqT
Bars40-45 dB LAeqT
Retail areas50-55 dB LAeqT
Manual workshops 55 dB LAeqT
Sound recording studios 30 dB LAeqT
Laboratories 40 dB LAeqT
Sports halls or swimming pools 55 dB LAeqT
Library areas40-50 dB LAeqT
Hotel bedrooms < 35 dB LAeqT
* Where ranges of noise levels are specified and privacy is not deemed by the final occupier to be an issue, it is acceptable to disregard the lower limit of the range and consider the noise level criteria to be lower than or equal to the upper limit of the range1 BS 8233 Sound insulation and noise reduction for buildings - Code of practice, 2014.

Table 21Guide to reverberation time, T, at 500 Hz in unoccupied rooms for speech and music

Room volume

Reverberation time T*

s

Speech

Music
500.41.0
1000.51.1
2000.61.2
5000.71.3
10000.91.5
20001.01.6
*Where the reverberation times stated above or in the referenced documents are not appropriate for the type of space or building being assessed, the acoustician must confirm why this is the case. In addition, the acoustician must set alternative appropriate reverberation times at the design stage and provide these to demonstrate compliance.

Table 22: Performance standards for reverberation in teaching and study spaces - mid-frequency reverberation time, Tmf, in finished but unoccupied and unfurnished rooms

Type of room

(receiving room)

Tmf (seconds)*

Open plan

Teaching areas

Resource areas

< 0.8

< 1.0

Lecture rooms

Small (fewer than 50 people)

Large (more than 50 people)

< 0.8

< 1.0

Recording studio0.6-1.2
Control room for recording< 0.5
Libraries< 1.0
Audio-visual, video conference rooms< 0.8
*Tmf is the arithmetic average of the reverberation times in the 500 Hz, 1 kHz and 2 kHz octave bands2Building Bulletin 93: Acoustic Design in Schools, A Design Guide, 2004, UK Department for Education & Employment.

Table 23: Airborne and impact sound insulation performance improvement standards for national legislation or standards

Credits

Credits awarded according to improvement over national legislation, standard or other defined baseline

Airborne sound insulation

dB

Impact sound insulation

dB

Individual bedrooms & self-contained dwellings
1Insulation values are at least 3dB higherInsulation values are at least 3dB lower*
3Insulation values are at least 5dB higherInsulation values are at least 5dB lower*
4Insulation values are at least 8dB higherInsulation values are at least 8dB lower*
*The index used to express impact sound insulation is usually based on the level of transmitted impact sound, such that a lower measured value indicates greater resistance to impact sound transmission. If the converse for the locally defined national index is true, the credit award will be based on the same performance increase as detailed for the airborne sound insulation and an accompanying statement from a SQA.

Table 24: Airborne and impact sound insulation performance standards

Credits

Credits awarded according to sound insulation performance standards

Airborne sound insulation

DnT,w + Ctr dB (minimum values)

Impact sound insulation

L'nT,w dB (maximum values)

Individual bedrooms & self-contained dwellings
14859
35057
45354

Compliance notes

Ref

Terms

Description

Shell and core (non-residential and residential institutions only)

CN1

Applicable assessment criteria

Indoor ambient noise criteria:

Both options: All criteria relevant to the building type and function apply (an alternative method to demonstrate compliance applies in this instance, refer to CN1.1 for further information).

Sound insulation and reverberation criteria:

Both options: These criteria are not applicable.

Refer to Appendix D – Shell and core project assessments for a more detailed description of the shell and core assessment options.

CN1.1

Alternative means of demonstrating compliance

The basic built form has a large impact on the acoustic performance of the building, and in the case of a shell only or shell and core development, this aspect of the build would be outside the control of the tenant. A SQA must carry out a quantifiable assessment of the specification of the build form, construction and any external factors that are likely to affect the indoor ambient noise levels. From this assessment, the SQA must confirm that given a typical arrangement and fit-out specification for the building type, the development is likely to meet the levels required to demonstrate compliance with the BREEAM criteria.

Where the specific room functions and areas within the building are yet to be defined, the acoustician must base their assessment on the most sensitive room type likely to be present in the building, as a worst case. For example, in a retail assessment, where there are likely to be offices, the acoustician should make an assessment based on this scenario.

One credit can be awarded where this has been achieved.

Residential - Partially fitted and fully fitted

CN2

Applicable assessment criteria - Single and multiple dwellings

Both options: Criteria 1 and 8 to10 only apply.

Refer to Appendix E – Applicability of BREEAM New Construction to single and multiple dwellings, partially and fully fitted for a more detailed description of residential assessment options.

CN2.1

Single dwelling

default case - Applies to detached dwellings

Four credits are available where there are no attached dwellings.

CN2.2

Attached multiple dwellings where separating walls or floors occur only between non-habitable rooms

Three credits are available.

Note: these criteria apply only to walls, floors and staircases that perform a dwelling to dwelling separating function. Internal partitions are beyond the scope of this issue.

Country-specific

CN3

Other appropriate good practice standards or regulations As detailed in the assessment criteria it is possible to use a national or local equivalent to the BREEAM requirements stated; however this must be approved by BRE Global. The Approved standards and weightings list can be used to check for previously approved standards or to propose a new national or local standard.

CN3.1

Building types without areas 'used for speech'Where a building type does not have areas 'used for speech', it does not need to comply with the relevant 'reverberation times' criteria. In these instances, the credit available for reverberation can be awarded by default where the building complies with the indoor ambient noise level and sound insulation criteria.

CN3.2

Acoustically sensitive rooms

Where the term 'acoustically sensitive rooms' is referenced in this BREEAM issue, it refers to any room or space the design team or client deems to be acoustically sensitive for the purposes of privacy, which may include the following types of spaces or rooms (where specified):

  1. Single and multiple occupancy offices
  2. Meeting, interview, consulting or treatment rooms
  3. Rooms used for public speaking or seminars
  4. Any other room or space the design team or client deems to be acoustically sensitive for the purposes of privacy.

CN3.3

Remedial worksWhere a programme of pre-completion testing identifies that spaces do not meet the standards, remedial works must be carried out prior to handover and occupation, and the spaces retested to ensure compliance. Remedial works must be carried out to all affected and potentially affected areas, including rooms or spaces previously untested of a similar construction and performance requirement. The test report, or covering correspondence, should include a clear statement that the testing is in accordance with the required standard (where specified) or the BREEAM criterion 3 and Methodology section, and include the relevant pass or fail criteria.

CN3.4

Privacy indexTo increase the ambient noise level, where privacy is required or the ambient targets include a minimum as well as maximum limit, an artificial sound source or sound masking system may be required. Any artificial sound source or sound masking system should be installed and in operation at the time of the acoustic testing to demonstrate compliance.

CN3.5

Reverberation timesWhere the reverberation time required by the relevant standard is not appropriate for the type of space or building being assessed, the SQA must confirm why this is the case. In addition the SQA must set alternative appropriate reverberation times at the design stage and provide these to demonstrate compliance.

CN3.6

Programme of testing

It is not acceptable to undertake a shorter test programme due to site readiness on the day of testing. If this issue arises additional testing should be scheduled. It may be that testing at less than the typical regime identified would be acceptable in some instances. Where this is the case, clear reasoning must be provided by the compliant test body prior to awarding the credits.

Building type specific

CN4

Long term stay residential institutions.

Rooms not covered by residential criteria.

Long term stay residential institutions often contain a mixture of 'non-residential' areas such as offices, small retail outlets, meeting rooms etc. and residential areas, e.g. self-contained dwellings or rooms for residential purposes.

Where less than 5% of the floor area of the assessed building includes 'non-residential' areas, these areas do not need to be assessed, hence only the residential spaces need to be assessed against the residential criteria to demonstrate compliance with criterion 8 .

Where more than 5% of the floor area of the assessed building includes areas other than self-contained dwellings or rooms for residential purposes:

  • If awarding 1 credit, only the self-contained dwellings or rooms for residential purposes need to be assessed to demonstrate compliance.
  • If awarding 3 or 4 credits the 'non-residential' areas must meet the relevant criteria for their function, and the self-contained dwellings or rooms for residential purposes need to be assessed to demonstrate compliance.

The calculation for the percentage of floor area that is 'non-residential' should only include occupied spaces (as defined in BREEAM issue Hea 01 Visual comfort).

CN4.1

Hotel type - Sound insulationBedrooms in hotels must be considered acoustically sensitive rooms. Sound insulation (DnT,w) for partitions and floors between rooms and between rooms and corridors should be > 50dB.

CN4.2

Residential only - Acoustic testing

Testing should be between habitable rooms on the ground floor and at higher storey levels, if applicable. Where there are not enough suitable separating walls or floors in a development to carry out the number of tests specified in the relevant national regulations or standards, all of the available suitable separating walls or floors must be tested.

Note: separating walls can be defined as those walls which separate dwellings.

CN4.3

Residential only - Mixed use developmentsFor mixed use developments where commercial premises share a separating wall or floor with residential spaces, a SQA shall propose an appropriate baseline performance making reference to national or international guidance, or good practice.

CN4.4

Residential only - Commercial space

Where a commercial space is separated from a dwelling or room for residential purposes by a separating wall or floor, testing shall be carried out between the commercial space and dwelling, with the commercial space being used as the source room irrespective of the volume.

CN4.5

Residential only - Pre-completion testing

No pre-completion testing is required where separating walls or floors only occur between non-habitable rooms, or non-habitable rooms and other spaces. In such cases, three credits can be awarded following an assessment by a SQA confirming that the constructions detailed would be capable of achieving the relevant performance requirements. No pre-completion testing is required where the dwellings are detached. In such cases, four credits can be awarded by default.

CN4.6

Residential only - Measurement proceduresAdditional information outlines the requirements for carrying out measurements and calculations to demonstrate compliance with this BREEAM issue. The appointed acoustician must confirm that the acoustic performance has been measured or calculated in accordance with these procedures. Where the acoustician has felt it necessary to deviate from these procedures, they must give justifiable reasons why they have done so.

Methodology

Testing, measurement and calculation procedures; non-residential only

Where specific guidance on testing, measurement and calculation is not stated in the criteria tables above for the relevant building type, or within the relevant standard or guidance referenced, the following procedures can be followed by the acoustician when measuring or calculating the levels required to demonstrate compliance with this BREEAM issue.

Measurements of sound insulation (airborne and impact) should be made in accordance with the relevant part of the ISO 16283 series. For measurements of reverberation time, the relevant principles of ISO 354:2003 should be used and the guidance provided in ISO 16283-1:2014 should be followed in respect of the number of source and microphone positions, and decay measurements. For measurements of ambient noise, when no specific guidance is available, the following procedures should be used.

  1. Noise from both internal sources (e.g. mechanical ventilation systems, plant noise, noise-making systems) and external sources (e.g. traffic noise transmitted via the building façade) should be included, and, where windows are openable as part of the ventilation strategy, these should be assumed to be open for the purposes of calculations and open for measurements. If openable windows are not part of the background or permanent ventilation strategy, then these should be assumed to be closed for the purposes of calculation and closed for measurements.
  2. Noise from occupants and office equipment (e.g. computers) should not be included in the measurements.
  3. Unless otherwise stated in the referenced document, a rate of testing of at least 1 in 10 rooms or spaces of each performance level shall be subject to on site performance testing.
  4. Measurements should be made in at least four rooms in which noise levels can be expected to be greatest either because they are on the noisiest façade or because they are on a naturally ventilated façade.
  5. Where different ventilation strategies are used, measurements should be conducted in rooms utilising each strategy. Otherwise, measurements should be made in rooms on the noisiest façade.
  6. T in LAeqT is taken as the duration of the normal working day (typically 8 hours between 09.00 and 17.00).
  7. Measurements need not be made over a period of 8 hours if a shorter measurement period can be used. In this case, measurements should be made when external noise levels are representative of normal conditions throughout the day.
  8. Measurement periods of less than 30 minutes may give representative values for indoor ambient noise levels and may be utilised where this is the case. However, measurement periods shorter than 5 minutes should not be used.
  9. Measurements should be taken in a minimum of three locations in rooms at a height of 1.2m above the floor level and at least 1m away from any surface.
  10. Where relevant, measurement of airborne sound insulation between teaching spaces should be conducted between one in four pairs of adjacent rooms (or teaching spaces) of each room type or performance requirement category and construction type.
  11. Where relevant, measurement of impact sound pressure level should be conducted in one in four teaching spaces (separated from rooms above) of each room type or performance requirement category and construction type.
  12. The measured level of ambient noise should be used to determine compliance with the criteria for acoustically sensitive rooms. If at the time of acoustic commissioning it is not possible to measure ambient noise levels in the absence of construction or other extraneous noise sources that will not be present when the building is complete, then, for mechanical services the lower level of 35 dB, LAeq or the lowest design limit for the acoustically sensitive space should be used.

The above is intended as guidance for undertaking acoustic testing or measurements to demonstrate compliance with the performance requirements in BREEAM. If the acoustician has felt it necessary to deviate from the above procedures, they should provide a reason for doing so and confirm that the alternative procedures are adequate for demonstrating that the building meets the acoustic performance requirements.

Testing, measurement and calculation procedures; residential buildings and long term stay residential institutions only

Frequency of testing

When the country does not have legislation regarding frequency of testing, the following guidance below sets out the number of airborne or impact sound insulation tests to be conducted on each group or sub-group. A unit is either a flat or a house. Where units contain a single habitable room, i.e. bedsits, the number of tests required is halved.

The following guidance and examples on how to define groups and sub-groups is provided:

Table 25: Composition of test set

Type of testingHousesApartments
Number of tests
Airborne sound insulation test of separating walls between units22
Airborne sound insulation test of separating floors between unitsN/A2
Impact sound insulation tests of separating floors between unitsN/A2

Example of testing series and compliance

Example 1

If a development consists of three houses; one set of tests will be required:

Example 2

If a development comprises 42 houses and 59 apartments; then five sets of tests between houses and 6 sets of tests between apartments will be required:

Evidence

CriteriaInterim design stageFinal Post-construction stage
All (non-residential type)

Professional report or study and calculations from the acoustician.

Letter of appointment or other confirmation demonstrating when the acoustician was appointed.

The relevant section or clauses of the building specification or contract, or a formal letter from the project team regarding commitments.

Professional field report or study and calculations from the acoustician post-construction demonstrating compliance with the relevant credit criteria.

Evidence, such as a formal letter from the acoustician or their test report confirming that they meet BREEAM’s definition of a SQA.

Where remediation works have been carried out, a professional field report or study and calculations from the acoustician post-completion of the works demonstrating compliance with the credit requirements.

All (residential buildings and residential institutions)

Where pre-completion testing will be carried out, a letter from the developer confirming the intent to:

  1. Meet the relevant sound insulation performance levels
  2. Use a compliant test body to complete testing.

Copies of the sound insulation field test results or a letter of confirmation that the required sound insulation performance standards as detailed in the assessment criteria have been achieved AND

Evidence that the tests have been carried out by a compliant test body.

Additional information

Relevant definitions

Acoustically sensitive rooms
Where the term 'acoustically sensitive rooms' is referenced in this BREEAM issue, it refers to any room or space the design team or client deems to be acoustically sensitive for the purposes of privacy, which may include the following types of space or rooms (where specified):
  1. Cellular offices
  2. Meeting, interview, consulting or treatment rooms.
In addition:
  1. Educational buildings or spaces: rooms for teaching and learning, i.e. classrooms, lecture theatres
  2. Rooms used for public speaking or seminars
  3. Any other room or space the design team or client deems to be acoustically sensitive for the purposes of privacy.
Compliant test body
A compliant test body is defined as:
  1. Organisations who are accredited by a member of the International Accreditation Forum (IAF: www.iaf.nu) to the appropriate scope OR
  2. Organisations who can provide evidence that they follow the relevant principles of ISO/IEC 17024 (Conformity assessment - General requirements for bodies operating certification of persons)3ISO/IEC 17024:2003 Conformity assessment - General requirements for bodies operating certification of persons in relation to BREEAM requirements.
Dw Weighted level difference
Single number quantity that characterises airborne sound insulation between rooms, but which is not adjusted to reference conditions. Note: Weighted level difference is used to characterise the insulation between rooms in a building as they are; values cannot normally be compared with measurements made under other conditions (see (EN) ISO 717-1).
Groups
Grouping should be carried out according to the following criteria; rooms for residential purposes should be considered as three separate groups. In addition, if significant differences in construction type occur within any of these groups, sub-groups should be established accordingly.
Sub-groups
Rooms for residential purposes; sub-grouping should be by type of separating floor and type of separating wall. The construction of flanking elements (i.e. elements above, below and on either side of the space, for example walls, floors, cavities) and their junctions are also important. Where there are significant differences between flanking details, further sub-grouping will be necessary. Sub-grouping may not be necessary for rooms for residential purposes that have the same separating wall or separating floor construction, with the same associated flanking constructions, and where the room dimensions and layouts are broadly similar. Some rooms for residential purposes may be considered to have unfavourable features; an example could be apartments with large areas of flanking wall without a window at the gable end. It would be inappropriate for these to be included as part of a group and these should form their own sub-groups.
Habitable rooms
For the purpose of this issue, habitable rooms include any room where individuals will sit or lie down, and require a reasonably quiet environment to concentrate or rest. Such rooms are bedrooms, living rooms, dining rooms, studies, as well as kitchen-dining and kitchen-living rooms.
Lightweight roofs
Roofs that have a mass per unit area less than 150kg/m2
Multiple occupancy offices
Office space that is not cellular in nature, i.e. it is open plan, and designed to accommodate more than two desk spaces or workstations.
Non-habitable rooms
For the purpose of this issue, non-habitable rooms include any room that is not considered a habitable room (as defined above). This includes rooms such as kitchens, bathrooms, toilets, hallways, garages and laundry rooms.
Occupied spaces
Refer to BREEAM issue Hea 01 Visual comfort and note that for BREEAM issue Hea 05 Acoustic performance there is a specific, unrelated, definition of Unoccupied spaces with reference to acoustic testing and measurement, see Compliance notes for details.
Pre-completion sound testing
Tests should be carried out once the build is essentially complete, but may be carried out prior to or post-decoration. In the case of dwellings, unless stated otherwise within relevant national building regulations or standards, the impact sound insulation tests should be carried out before floor finishes such as carpets, wood flooring or vinyl coverings have been installed.
Room for residential purposes
A room, or a suite of rooms which is not a dwelling (house or a flat) and which is used by one or more persons to live and sleep. It includes a room in a hostel, hotel, boarding house, hall of residence or residential home, whether or not the room is separated from or arranged in a cluster group with other rooms, but does not include a room in a hospital, or other similar establishment, used for patient accommodation.
Suitably qualified acoustician (SQA)
An individual achieving all the following items can be considered to be 'suitably qualified' for the purposes of a BREEAM assessment.
  1. Holds a degree, PhD or equivalent qualification in acoustic or sound testing.
  2. Has a minimum of three years relevant experience (within the last five years). Such experience must clearly demonstrate a practical understanding of factors affecting acoustics in relation to construction and the built environment; including acting in an advisory capacity to provide recommendations for suitable acoustic performance levels and mitigation measures.
  3. An individual who holds a recognised acoustic qualification and membership of an appropriate professional body.
Where a SQA is verifying the acoustic measurements or calculations carried out by another acoustician who does not meet the SQA requirements, they must, as a minimum, have read and reviewed the report and confirm in writing that they have found it to:
  1. Represent sound industry practice
  2. Be appropriate given the building being assessed and scope of works proposed
  3. Avoid invalid, biased and exaggerated recommendations.
Additionally, written confirmation from the third party verifier that they comply with the definition of a SQA is required.
Single occupancy offices
Cellular office space designed to accommodate one or two desk spaces or workstations (typically no greater than 10m²).
Unoccupied spaces
Where the term 'unoccupied space' is referenced in this BREEAM issue it refers to the nature of the space for the purpose of carrying acoustic calculations or measurements, i.e. such measurements must be carried out when the space is unoccupied and therefore devoid of any sources of noise.
Weighted standardised level differences (DnT,w)
HTM 08-01 defines this as the 'unit for rating airborne sound insulation on-site'.
Weighted standardised impact sound pressure level (LnT,w)
HTM 08-01 defines this as the 'unit for rating impact airborne sound insulation on-site'.

Other information

Noise rating (NR) curves

Noise assessments based on NR curves are often used by building services consultants to predict internal noise levels due to mechanical ventilation systems. However, the BREEAM requirement uses the indoor ambient noise level, LAeq,T which includes external noise transmitted via the façade as well as internal noise such as that from mechanical ventilation systems. In the absence of strong low frequency noise, LAeq,T can be estimated from the NR value using the following formula: LAeq,T NR + 6 dB. Therefore, if the NR value is known, but not the sound pressure levels in the individual frequency bands, an estimate for the indoor ambient noise level LAeq,T can still be determined from the NR value for the building services noise. The LAeq,T for the external noise transmitted via the façade must then be combined with the LAeq,T for the building services.

BREEAM International New Construction 2016
Reference: SD233 – Issue: 2.0
Date: 03/07/2017
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