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NOISE IMPACT ASSESSMENT
PROJECT: IFIELD ROAD, CRAWLEY
CLIENT: SLOANE CRAWLEY PROPERTIES LTD
CLIENT ADDRESS: BERKELEY SQUARE HOUSE
BERKELEY SQUARE
MAYFAIR
LONDON
W1J 6BD
COMPANY ADDRESS: CASS ALLEN ASSOCIATES
BEDFORD I-LAB
PRIORY BUSINESS PARK
BEDFORD
MK44 3RZ
DOCUMENT CONTROL:
This report has been prepared by Cass Allen Associates Ltd with all reasonable skill, care and diligence, and taking account of the
resources devoted to it by agreement with the client. Information reported herein is based on the interpretation of data collected and has
been accepted in good faith as being accurate and valid. This report is for the exclusive use of the client named above; no warranties or
guarantees are expressed or should be inferred by any third parties. This report may not be relied upon by other parties without written
consent from Cass Allen Associates. Cass Allen Associates disclaims any responsibility to the client and others in respect of any matters
outside the agreed scope of work.
REVISION ISSUE DATE REPORT BY CHECKED BY NOTES
0 09 December 2014 Adam Bamford, BSc MIOA
DipIOA, Acoustics Consultant
Sam Bryant, MPhys AMIOA,
Acoustics Consultant
Draft issue for comment
1 18 December 2014 Adam Bamford, BSc MIOA
DipIOA, Acoustics Consultant
Sam Bryant, MPhys AMIOA,
Acoustics Consultant
Planning issue, incorporating comments from project team
Project: Ifield Road, Crawley Client: Sloane Crawley Properties Ltd Ref: RP01-14545
Web: www.cassallen.co.uk Tel: 01234 834 862
Page: 1 of 16
TABLE OF CONTENTS
1. INTRODUCTION
2. PROJECT DESCRIPTION
3. PLANNING POLICY
4. NOISE AFFECTING THE DEVELOPMENT
5. PLANT NOISE IMPACT ASSESSMENT
6. NOISE BREAKOUT FROM THE HOTEL PLANT ROOM
7. CONCLUSIONS
GLOSSARY
CURRENT DEVELOPMENT DRAWINGS
SURVEY RESULTS
CAA NOISE CONTOURS FOR A 2 RUNWAY FUTURE SCENARIO AT LONDON GATWICK AIRPORT
FACSIM CALCULATIONS
Project: Ifield Road, Crawley Client: Sloane Crawley Properties Ltd Ref: RP01-14545
Web: www.cassallen.co.uk Tel: 01234 834 862
Page: 2 of 16
1. INTRODUCTION
1.1 Cass Allen Associates has been instructed by Sloane Crawley Properties Ltd to assess the
suitability of the site located at 27-45 Ifield Road, West Green in Crawley for a proposed mixed use
redevelopment with respect to noise.
1.2 The assessment has been carried out in accordance with relevant local and national planning
guidance.
1.3 The aims of the assessment were:
To establish the suitability of existing noise levels at the site for the proposed
development; and
Where required, identify appropriate mitigation measures to achieve acceptable noise
levels in the finished development.
1.4 This report contains technical terminology; a glossary can be found in Appendix 1.
Project: Ifield Road, Crawley Client: Sloane Crawley Properties Ltd Ref: RP01-14545
Web: www.cassallen.co.uk Tel: 01234 834 862
Page: 3 of 16
2. PROJECT DESCRIPTION
2.1 The site currently contains a surface car park and is located in a predominantly residential area,
containing some commercial uses. The site is bounded to the north by West Green Drive, to the
east by a strategic roundabout that forms a link to Crawley town centre, to the south by Ifield Road
and to the west by existing two storey residential dwellings. The site is located approximately 3.5km
due south of Gatwick Airport.
2.2 An annotated site location plan is shown in Figure 1 below.
Figure 1 Annotated Site Location Plan
2.3 The proposals involve the redevelopment of the site to provide residential dwellings; including a
mixture of 1-bed and 2-bed apartments, an apart-hotel and associated car parking provisions.
Relevant current drawings of the proposed development layouts are shown in Appendix 2.
Site
Project: Ifield Road, Crawley Client: Sloane Crawley Properties Ltd Ref: RP01-14545
Web: www.cassallen.co.uk Tel: 01234 834 862
Page: 4 of 16
3. PLANNING POLICY
National Policy
3.1 Outline guidance for the assessment of noise affecting new developments is given in the National
Planning Policy Framework (NPPF). Section 109 of the NPPF states:
The planning system should contribute to and enhance the natural and local environment
by…preventing both new and existing development from contributing to or being put at
unacceptable risk from, or being adversely affected by, unacceptable levels of…noise
pollution.
and in section 123:
Planning policies and decisions should aim to:
avoid noise from giving rise to significant adverse impacts on health and quality of life as
a result of new development;
mitigate and reduce… other adverse impacts on health and quality of life arising from noise
from new development, including through the use of conditions;
recognise that development will often create some noise and existing businesses wanting
to develop in continuance of their business should not have unreasonable restrictions put
on them because of changes in nearby land uses since they were established;
and identify and protect areas of tranquillity which have remained relatively undisturbed by
noise and are prized for their recreational and amenity value for this reason”.
Noise Policy Statement for England
3.2 The Noise Policy Statement for England (NPSE) was published in March 2010 and seeks to clarify
the underlying principles and aims in policy documents, legislation and guidance that relate to
noise. It also sets out the long term vision of Government noise policy:
To promote good health and a good quality of life through the effective management of
noise within the context of Government policy on sustainable development.
3.3 The NPSE clarifies that noise should not be considered in isolation of the wider benefits of a
scheme or development, and that the intention is to minimise noise and noise effects as far as is
reasonably practicable having regard to the underlying principles of sustainable development.
3.4 The explanatory note of NPSE defines the terms used in the NPPF:
2.20: There are two established concepts from toxicology that are currently being applied
to noise impacts, for example, by the World Health Organisation. They are:
Project: Ifield Road, Crawley Client: Sloane Crawley Properties Ltd Ref: RP01-14545
Web: www.cassallen.co.uk Tel: 01234 834 862
Page: 5 of 16
NOEL – No Observed Effect Level
This is the level below which no effect can be detected. In simple terms, below this level,
there is no detectable effect on health and quality of life due to the noise.
LOAEL – Lowest Observed Adverse Effect Level
This is the level above which adverse effects on health and quality of life can be detected.
2.21: Extending these concepts for the purpose of this NPSE leads to the concept of a
significant observed adverse effect level.
SOAEL – Significant Observed Adverse Effect Level
This is the level above which significant adverse effects on health and quality of life occur.
3.5 The NPSE does not define the SOAEL numerically, stating in paragraph 2.22:
It is not possible to have a single objective noise-based measure that defines SOAEL that
is applicable to all sources of noise in all situations. Consequently, the SOAEL is likely to
be different for different noise sources, for different receptors and at different times. It is
acknowledged that further research is required to increase our understanding of what may
constitute a significant adverse impact on health and quality of life from noise. However,
not having specific SOAEL values in the NPSE provides the necessary policy flexibility
until further evidence and suitable guidance is available.
Local policy
3.6 Adopted local planning policy (consisting of the Core Strategy 2008 Revision and ‘saved’ policies
of the Crawley Local Plan 2000) seeks to ensure a high standard of design and amenity with all
new development, however does not provide detailed guidance on noise. However, the emerging
Local Plan includes planning policies to guide development within the borough in respect of noise
and Policy ENV11 (Development and Noise) is relevant to this application. Relevant excerpts of
this policy are stated below:
Noise Sensitive Development
Noise sensitive uses proposed in areas that are exposed to significant noise from existing
or future transport sources (air, road, rail and mixed sources) will be permitted where it
can be demonstrated that future users will not be exposed to an unacceptable noise
impact. Levels set out in the Local Plan Noise Annex will establish if the proposal is
acceptable in noise impact terms.
Mitigating Noise Impact
Where proposals are identified as being subject to significant or unacceptable noise
impact, either through noise exposure or generation, the best practical means of mitigation
must be employed to mitigate noise impact to an appropriate level. Proposals that do not
appropriately mitigate against unacceptable noise impact through the design and planning
process will be refused.
Project: Ifield Road, Crawley Client: Sloane Crawley Properties Ltd Ref: RP01-14545
Web: www.cassallen.co.uk Tel: 01234 834 862
Page: 6 of 16
3.8 To address the requirements of the national and local policies, the following key acoustic matters
have been assessed:
Noise affecting the habitable areas of the proposed development;
Noise emissions from mechanical plant associated with the development at both the
position of existing sensitive receptors in the area and future dwellings associated with
the development itself; and
Noise breakout from the proposed hotel plant room to the guest rooms located above.
3.9 The above matters are discussed in turn in the following sections of this report.
Project: Ifield Road, Crawley Client: Sloane Crawley Properties Ltd Ref: RP01-14545
Web: www.cassallen.co.uk Tel: 01234 834 862
Page: 7 of 16
4. NOISE AFFECTING THE DEVELOPMENT
4.1 The noise levels that will exist within the habitable areas of the finished development have been
predicted based on the existing noise environment at the site and outline details for the design of
the development. The predicted noise levels have then been compared with appropriate design
criteria. Where the criteria have been predicted to be exceeded, suitable mitigation measures have
been identified.
Design criteria – Internal noise levels
4.2 Appropriate design criteria for acceptable noise levels in acoustically sensitive areas of new
developments are given in the Crawley Local Plan Noise Annex within Crawley 2030 – The Crawley
Borough Local Plan 2015-2030. The relevant design criteria for noise sensitive development
affected by noise from transport sources (which is applicable to this application) are summarised
in Table 1.
Table 1 Standards for Noise Sensitive Development Affected by Noise from Transport
Sources from the Noise Annex of Crawley Borough Council’s Local Plan
Project: Ifield Road, Crawley Client: Sloane Crawley Properties Ltd Ref: RP01-14545
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Page: 8 of 16
4.3 In addition to the above, British Standard 8233:2014 ‘Guidance on sound insulation and noise
reduction for buildings’ (BS8233) also provides up to date guidance on suitable internal noise levels
within buildings. This has been referred to where appropriate.
4.4 It is also considered appropriate in this case to assess the potential impact of noise emissions from
individual vehicle pass-bys on the bedrooms of the development during the night-time. This is in
line with guidance given in the World Health Organisation (WHO) document Guidelines for
community noise, which recommends that noise exceeding 45dB LAFmax should be limited, if
possible and that for a good sleep, it is believed that indoor sound pressure levels should not
exceed 45dB LAmax more than 10-15 times per night.
4.5 BS8233 also advises that it is desirable that noise levels in external amenity areas of residential
developments do not exceed 50 dB LAeq and that 55 dB LAeq,T should be regarded as a upper
guideline value. However, the Standard recognises that these guideline values will not always be
achievable in city centres or urban areas adjoining main roads or other transport sources. In these
cases, BS8233 advises that the development should be designed to achieve the lowest practical
noise levels in the amenity spaces.
4.6 The following acoustic design criteria have therefore been adopted for the development:
Average noise levels in living rooms and dining rooms during the day should not exceed
35 dB LAeq,0700-2300hrs and 40 dB LAeq,0700-2300hrs respectively;
Average noise levels in bedrooms should not exceed 35 dB LAeq,0700-2300hrs during
the day 30 dB LAeq,2300-0700hrs during the night;
Maximum noise levels should not regularly exceed 45 dB LAmax in bedrooms during the
night;
Where possible, average noise levels in external amenity areas during the day should be
lower than 50-55 dB LAeq,0700-2300hrs.
Existing site noise levels
4.7 A noise survey was carried out at the site between 18th and 19th November 2014 to assess typical
existing noise levels in the area. The full methodology and results of the noise survey are provided
in Appendix 3.
4.8 Average noise levels (LAeq) across the site were generally dictated by road traffic on West Green
Drive and Ifield Road. Background noise levels (LA90) across the site were dictated by constant
road traffic noise from the surrounding road network.
4.9 Maximum noise levels (LAFmax) along the northern and southern site boundaries were dictated
by individual vehicle movements on West Green Drive and Ifield Road respectively.
4.10 Measurable noise from aircraft movements was not identified during the survey. Furthermore, the
site lies outside the noise contours produced by the Civil Aviation Authority for a 2 runway future
scenario at London Gatwick airport (see Appendix 4). Therefore, in our view, noise from aircraft
associated with London Gatwick airport will be insignificant in comparison to road traffic noise.
Project: Ifield Road, Crawley Client: Sloane Crawley Properties Ltd Ref: RP01-14545
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Page: 9 of 16
4.12 The noise survey results show that the northern boundary of the site directly overlooking West
Green Road will be subject to the highest incident noise levels. Existing typical free-field noise
levels at this position (measurement position L1 – Appendix 3) are as follows:
Average noise levels during the daytime - 67 dB LAeq,0700-2300hrs;
Average noise levels during the night-time - 58 dB LAeq,2300-0700hrs;
Typical maximum noise levels during the night-time - 80 dB LAFmax.
4.13 The southern boundary of the site directly overlooking Ifield Road was found to be subject to lower
incident noise levels than the northern boundary. Existing typical free-field noise levels at
measurement position L2 are as follows:
Average noise levels during the daytime - 64 dB LAeq,0700-2300hrs;
Average noise levels during the night-time - 57 dB LAeq,2300-0700hrs;
Typical maximum noise levels during the night-time - 75 dB LAFmax.
Internal noise levels in noise-sensitive rooms
4.14 Full construction details for the development have not been finalised as the project is at an early
design stage. It has therefore been assumed that the external walls of the development will be
constructed using a standard masonry construction (e.g. 102mm brick, 100mm insulated cavity,
100mm concrete block) or a light-weight construction designed to achieve a similar level of sound
insulation (this is technically achievable subject to detailed design). Consequently, internal noise
levels would be dictated by external noise ingress via glazing and ventilators.
4.15 The ventilation scheme for the project has not yet been decided and therefore, for the purpose of
the assessment, it has been assumed that the residential units will be ventilated via a continuous
mechanical extract system in wet rooms and background ventilators in the external facades, with
openable windows for the provision of purge ventilation (as per System 3 from Building Regulations
Part F).
4.16 It is assumed that the ventilation scheme for the proposed hotel will be Mechanical Ventilation with
Heat Recovery (MVHR) i.e. System 4 from Building Regulations Part F. Therefore, there will be no
background ventilators in the external façades of the hotel (e.g. trickle ventilators etc).
4.17 The MVHR system should be selected to ensure that noise from air supply and extract ductwork
does not exceed acceptable levels within habitable rooms. Appropriate specifications for noise
levels from the MVHR system (operating at typical maximum duty) would be as follows:
Guest bedrooms – NR 25 dB at 1.5m from any ventilation aperture;
Staff/meeting/training rooms – Between NR 30-40 dB at 1.5m from any ventilation
aperture
4.18 The MVHR system will also need to be specified to ensure that sufficient ventilation rates can be
provided with windows closed to prevent units overheating in summer months.
Project: Ifield Road, Crawley Client: Sloane Crawley Properties Ltd Ref: RP01-14545
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4.19 Calculations were carried out using façade modelling software in accordance with the “more
rigorous” methodology given in BS8233 to calculate the sound insulation performance required of
the glazing and ventilation to achieve the nominated internal noise criteria in the ‘worst-case’
habitable rooms of the development (i.e. the habitable rooms that will be subject to the highest
external noise levels).
4.20 If acceptable internal noise levels can be achieved in ‘worst case’ habitable rooms then it follows
that acceptable internal noise levels can be achieved in all other habitable rooms of the
development using similar glazing and ventilator types.
4.21 The calculations were carried out for two ‘worst case’ scenarios. The first scenario is based on the
typical known dimensions/details for facade elements within habitable rooms of the proposed
residential dwellings. The second scenario is based on the typical known dimensions/details for
façade elements within habitable rooms of the proposed hotel.
Scenario 1
Glazing – 2.5m2 for bedrooms and 6m2 for living rooms;
External walls – 3.7m2 for bedrooms and 4.6m2 for living rooms; and
2 in-frame trickle ventilators in bedrooms and 3 in-frame trickle ventilators in living rooms.
Scenario 2
Glazing – 2.5m2 for bedrooms and 6m2 for living rooms;
External walls – 3.7m2 for bedrooms and 4.6m2 for living rooms; and
4.22 The results of the calculations are shown in Appendix 5 and are summarised in Tables 2 and 3.
Table 2 Acoustic Requirements for ‘Worst Case’ Habitable Rooms within Residential Dwellings
‘Worst Case’ Rooms Glazing Performance
Requirements (inc. Frames)
Ventilator Performance
Requirements
Bedrooms facing West Green
Road façade
(2300-0700hrs)
37 dB Rw+Ctr 44 dB Dne,w + Ctr
Living rooms facing West Green
Road façade
(0700-2300hrs)
37 dB Rw+Ctr 44 dB Dne,w + Ctr
Note The requirements given are approximate only and should be confirmed at the
detailed design stage when full design details are available.
Project: Ifield Road, Crawley Client: Sloane Crawley Properties Ltd Ref: RP01-14545
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Page: 11 of 16
Table 3 Acoustic Requirements for ‘Worst Case’ Guest Bedrooms within Hotel
‘Worst Case’ Rooms Glazing Performance Requirements (inc. Frames)
Bedrooms facing West Green Road façade
(2300-0700hrs)
33 dB Rw+Ctr
Note The requirements given are approximate only and should be confirmed at the detailed
design stage when full design details are available.
4.24 The required sound insulation performance values in Tables 2 and 3 could typically be achieved
by the glazing and ventilator types shown in Table 4.
Table 4 Typical Glazing / Ventilator Acoustic Performances
Glazing (in Good Quality Sealed Frames) Typical Weighted Sound Reduction
(Rw + Ctr)
8.8mm/16/4mm acoustically upgraded thermal double glazing 33
10mm/16/8.8mm acoustically upgraded thermal double glazing 37
Ventilators Typical Acoustic Performance
(Dnew + Ctr)
Greenwood AAB4000 through wall acoustic ventilator 44
Greenwood Airvac MA3051 through wall acoustic ventilator 52
4.25 It can be seen from the above that acceptable internal noise levels will be achievable in the
development, subject to the specification of suitable glazing and ventilation systems at the detailed
design stage (which could be secured with a suitable planning condition). It is our view therefore
that the proposed development is, in principle, acceptable with regards to the noise levels that will
exist within the habitable rooms.
4.26 It should be noted that it will be possible to use lower acoustic performance façade elements for
façades that are further from or acoustically screened from the surrounding noise sources. This
could be investigated further at the detailed design stage.
Project: Ifield Road, Crawley Client: Sloane Crawley Properties Ltd Ref: RP01-14545
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Page: 12 of 16
Noise levels in external amenity areas
4.27 The layout of the development has also been reviewed in relation to the BS8233 recommendation
that noise levels in external amenity areas should ideally not exceed 50 – 55 dB LAeq,T.
4.28 Based on the results of the environmental noise survey, noise levels on balconies on the façades
directly overlooking West Green Road and Ifield Road would be expected to exceed the BS8233
recommended levels by approximately 9-17 dBA depending on height and aspect. However, whilst
this is not ideal, in our view, exceeding the BS8233 recommended levels does not normally mean
that the balconies would be unacceptable to future residents. The reasons for this are as follows:
Most developments in urban areas will be subject to noise levels above the BS8233
recommended levels for balconies1.
It is common for noise levels on balconies facing main roads to exceed the BS8233
recommended noise levels in Crawley and elsewhere;
It is reasonable to assume that residents would prefer the option to have a noisier balcony
as opposed to having no balcony at all;
In this case all residents will have the use of the ground floor level communal amenity
areas between the blocks where the predicted noise levels are lower than the BS8233
‘desirable’ levels;
The balconies will have glass balustrades, which will reduce the road traffic noise levels
on the balconies as far as is practicable. There are no other noise mitigation measures
available for balconies other than fully enclosing them (‘winter gardens), which essentially
changes the balconies into internal rooms; and,
Planners often consider it to be beneficial to the street-scape to have balconies facing
roads as they help marry the development to the surrounding area.
The current design of the development is therefore considered to be acceptable in relation to noise levels
in external amenity areas.
1 Table 2 from BS8233 notes that daytime noise levels will typically exceed 50-55 dB LAeq,16hr in areas close to busy main
roads. It was also found in the UK National Noise Incidence Study 2000/2001 that 90% of UK homes were exposed to daytime
noise levels >50dB LAeq,16hr and 54% of UK homes were exposed to noise >55dB LAeq,16hr. It is reasonable to assume that
a high percentage of these were in urban areas.
Project: Ifield Road, Crawley Client: Sloane Crawley Properties Ltd Ref: RP01-14545
Web: www.cassallen.co.uk Tel: 01234 834 862
Page: 13 of 16
5. PLANT NOISE IMPACT ASSESSMENT
5.1 It will be important to ensure that noise emissions from external mechanical plant associated with
the development will not disturb either nearby existing noise sensitive receptors, or future noise
sensitive receptors associated with the development itself.
Design criteria – Mechanical plant noise
5.2 BS4142:2014 – Methods for rating and assessing industrial and commercial sound (BS4142) can
be used to assess the impact of a new industrial and/or commercial noise source(s) on nearby
sensitive receptors.
5.3 The BS4142 assessment methodology can be summarised as follows:
1. Measure the existing background noise levels (LA90,T dB) at the locations of nearby
noise sensitive receptors during the quietest periods when the noise source(s) under
investigation will operate;
2. Predict or measure the noise emissions (LAeq,T dB) from the noise source(s) under
investigation at the location(s) of the nearby sensitive receptors, including corrections for
any distinguishable acoustic features (e.g. tones, whines, screeches, hisses etc);
3. Subtract the measured background noise levels (item 1 above) with the measured or
predicted rating noise levels (item 2 above) at each sensitive receptor. BS4142 states
that:
a) Typically, the greater this difference, the greater the magnitude of the impact.
b) A difference of around +10 dB or more is likely to be an indication of a significant
adverse impact, depending on the context.
c) A difference of around +5 dB is likely to be an indication of an adverse impact,
depending on the context.
d) The lower the rating level is relative to the measured background sound level, the less
likely it is that the specific sound source will have an adverse impact or a significant
adverse impact. Where the rating level does not exceed the background sound level, this
is an indication of the specific sound source having a low impact, depending on the
context.
NOTE Adverse impacts include, but are not limited to, annoyance and sleep disturbance.
Not all adverse impacts will lead to complaints and not every complaint is proof of an
adverse impact.
5.4 CBC’s planning policy requires that all new fixed plant and machinery is designed to achieve a
rating level at least 10 dB below the existing background noise level at surrounding sensitive
receptors.
5.5 Typical background noise levels (LA90) at the site were measured as part of the site noise survey
outlined in Appendix 3. The measured background noise levels have been used to develop limits
for plant noise emissions from the new development at the positions of the surrounding residential
properties in accordance with the BS4142 assessment methodology. The limits are shown in Table
5.
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Table 5 BS4142 Noise Limits - Free-field Levels
Location Period
Day-time/Evening (0700-
2300hrs)
Night-time (2300-0700hrs)
Nearest residential properties to
proposed development (approximately
25m
45 dB LAeq 27 dB LAeq
Note 1 The above limits assume that the fixed plant will not have any distinctive acoustic features (e.g. tones,
impulses, intermittency etc)
Proposed mechanical plant design
5.6 Detailed design information is not yet available for external mechanical plant for the development,
and therefore noise emissions from external mechanical plant cannot be accurately predicted at
the positions of nearby residential properties at this stage.
5.7 It is expected that it will be straightforward to achieve the BS4142 daytime noise limits given the
high background noise levels. However, mitigation measures (i.e. a suitable acoustic enclosure,
equipment with a lower noise emission ‘night mode’ etc.) may need to be incorporated into the
design in order to achieve the night-time limits for mechanical fixed plant.
5.8 The selection and design of external mechanical plant will be reviewed as information becomes
available to ensure that the project BS4142 noise limits given in Table 5 are achieved. Compliance
with the limits could be secured through the imposition of a suitable planning condition if deemed
necessary by the Local Planning Authority.
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6. NOISE BREAKOUT FROM THE HOTEL PLANT ROOM
6.1 It is noted that there is a plant room on the ground floor of the proposed hotel with guest bedrooms
located on the floor above.
6.2 Noise and vibration emissions associated with the plant room cannot be fully assessed until full
details of proposed plant are known. However, it is generally straightforward to control noise and
vibration within plant rooms using the following noise mitigation measures:
Designing high acoustic performance separating walls and floors between the plant room
and the residential units above; and,
Isolating any sources of vibration with appropriate anti-vibration mounts to minimise
structure borne noise and vibration.
6.3 The above measures can be investigated further at the detailed design stage and this could also
be secured through the imposition of a suitable planning condition if deemed necessary by the
Local Planning Authority.
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Page: 16 of 16
7. CONCLUSIONS
7.1 Cass Allen Associates was instructed by Sloane Crawley Properties Ltd assess the suitability of
the site for the proposed development with regards to noise.
7.2 The assessment was carried out in accordance with relevant local and national planning guidance.
7.3 A noise survey was carried out at the site between 18th and 19th November 2014. Noise levels
across the site were generally dictated by road traffic sources on West Green Drive and Ifield Road.
7.4 Acceptable internal noise levels are predicted to be achieved inside the worst-case habitable rooms
of the flats within the development subject to the adoption of commercially available acoustically
upgraded glazing and ventilation in the development design.
7.5 Based on the results of the environmental noise survey, noise levels on balconies on the façades
directly overlooking West Green Road and Ifield Road would be expected to exceed the BS8233
suggested levels. However, whilst this is clearly not ideal, BS8233 recognises that where
exceedances are found, the development should be designed to achieve the lowest practicable
noise levels in external amenity spaces. This has been taken into consideration in the assessment.
7.6 Appropriate limits for noise from mechanical plant have been calculated based on measured typical
noise levels at the site and guidance given in BS4142. It is envisaged that it will be straightforward
to achieve the plant noise limits, subject to the specification of mechanical plant and mitigation
measures (if required) at the detailed design stage.
7.7 Noise breakout from the proposed hotel plant room cannot be fully assessed until full details of the
proposed plant are known. However, it is generally straightforward to control noise and vibration
emissions within plant rooms, subject to the incorporation of suitable mitigation measures (if
required) at the detailed design stage.
7.8 In summary of the above it is our view that the site is suitable for the development in terms of noise.
Glossary
Term Explanation
Noise
Sound that is unpleasant or that causes (or could cause) disturbance or annoyance. Noise is
assessed in terms of sound pressure levels.
dB (decibel) The standard unit for defining sound pressure levels. The lower threshold of normal hearing is in the
region of 0dB. 130dB is the upper threshold of pain.
A change of 1dB in sound pressure levels is only perceptible under controlled conditions. The
minimum perceptible change under normal conditions is 3dB. A change of 5dB would be clearly
noticeable to the average listener. A change of 10dB roughly corresponds to a subjective ‘halving’ or
‘doubling’ of loudness.
The decibel is a logarithmic quantity, meaning the normal arithmetic rules of mathematics cannot be
directly applied. For example:
30dB + 30dB ≈ 33dB;
3 x 20dB ≈ 25dB, and;
40dB – 25dB ≈ 40dB
dBA (A-weighted
decibel)
A-weighted decibels have been corrected
using a frequency weighting (A-weighting) that
broadly corresponds with the hearing
response of the human ear. Measurements of
noise in dBA are generally used for assessing
people’s perception of noise.
The table on the right shows indicative A-
weighted noise levels (sound pressure levels)
from a variety of sources.
Source, distance Level (dBA)
Jet aircraft, 50m away 140
Threshold of pain 130
Threshold of discomfort 120
Chainsaw, 1m distance 110
Disco, 1m from speaker 100
Diesel truck, 10m away 90
Kerbside of busy road, 5m 80
Vacuum cleaner, distance 1m 70
Conversational speech, 1m 60
Average home 50
Quiet library 40
Quiet bedroom at night 30
Background in TV studio 20
Rustling leaves in the distance 10
Threshold of human hearing 0
LAeq,T (equivalent
continuous noise level)
The sound level of a notionally steady sound having the same energy as the A-weighted fluctuating
sound over the measurement period (T). The A-weighted equivalent continuous noise level (LAeq) is
commonly used to describe the “average” or “ambient” noise level in a given environment over the
measurement period.
LA10,T The A-weighted level of noise exceeded for 10% of the specified measurement period (T). It gives an
indication of the upper limit of fluctuating noise and is commonly used to describe road traffic noise
levels. LA10,18h is the arithmetic average of the 18 hourly LA10,1h values from 06.00 to 24.00 (defined
in CRTN).
LA90,T The A weighted noise level exceeded for 90% of the specified measurement period (T). It is
commonly used to define “background” noise level, i.e. the underlying noise level in the absence of
intermittent or short-duration noises.
Term Explanation
LAmax (maximum noise
level)
The highest A-weighted noise level recorded during the measurement period. Unless described
otherwise, it is generally measured using the ‘fast’ sound level meter response.
Hz (Hertz) Hz are the unit of frequency, equal to one cycle per second. Frequency of sound waves refers to the
number of pressure fluctuations per second. Frequency is related to the pitch of a sound.
Octave-band or
third-octave
band (1/1 or 1/3)
The spectrum of audible frequencies can be separated into proportional ‘bands’ to facilitate ease of
computation and analysis (the bandwidth being proportional to the band centre-frequency). Third-
octave bands (1/3-octave) split each octave into 3 bands, which allows greater accuracy.
Free-field A sound field determined at a point away from reflective surfaces other than ground with no significant
contributions due to sound from other reflective surfaces. Generally as measured outside and away
from buildings.
Facade-level A measurement taken in close proximity (e.g. 1m) to a reflective surface (other than ground) such as
a building facade. It is generally accepted that reflections from the surface will increase the measured
noise levels by around 3 dB compared to free-field levels, i.e. free-field levels = facade levels – 3 dB.
Reverberation The sound in a room or enclosed space that results from reflections from the room boundaries. The
reverberation time (RT) is the time required for the steady sound pressure level in an enclosed space
to decay by 60dB.
Sound absorption The process whereby sound energy is converted into heat, leading to a reduction in the sound
pressure level. Directly related to reverberation in an enclosed space, i.e. more absorption = lower
reverberant level and shorter reverberation time.
Sound insulation A general term referring to the degree by which a material or separating construction reduces sound
energy passing through it.
Dw (weighted sound level
difference)
Describes the weighted sound level difference between a source room and receiving room when
noise is being generated in the source room. Used to assess and describe the sound insulation
between the two rooms. DnTw is the sound level difference normalised to a reference reverberation
time (0.5 seconds unless stated otherwise).
Lw (weighted sound level
difference)
Describes the weighted impact sound insulation of a floor. Impact sound is sound caused by physical
impacts (such as footfall) on the floor. Impact sound insulation is quantified by placing a ‘tapping
machine’ on top of the floor and measuring the resultant noise levels in rooms below. LnTw is the
sound level difference normalised to a reference reverberation time (0.5 seconds unless stated
otherwise).
Rw (Weighted sound
reduction index)
The weighted sound reduction index (see SRI entry below) is a single number laboratory-measured
rating used to describe the sound insulation performance of building elements. The R’w is the
apparent sound reduction index measured onsite (normally tends to lower than the laboratory rated
Rw level due to onsite conditions).
SRI (Sound Reduction
Index)
A laboratory-measured rating of the airborne sound insulation properties of building elements across
various frequencies.
NR (Noise Rating) Noise rating is a method for assigning a single number level to a noise spectrum. It is typically used
to specify allowable noise emissions from mechanical ventilation systems in buildings. For a typical
noise spectrum the NR level is approximately equivalent to the dBA level minus 6, i.e. NR ≈ dBA –
6.
Survey Results
Survey Summary: The survey comprised short-term operator attended noise measurements and longer-term
unattended noise monitoring at the site. Noise levels at the site were generally dictated by road traffic
on surrounding roads. Vibration levels at the site were very low.
Survey
Period:
18/11/2014 to 19/11/2014
Survey Objectives:
To identify noise sources that contribute to ambient noise levels at the site;
To measure noise levels around the site over a typical day and night-time period.
Equipment Used: Type Manufacturer Model Serial Number
Sound level meter1 Bruel & Kjaer 2250 2630237
Calibrator Bruel & Kjaer 4231 2115551
Sound level meter1
(noise logger)
Rion NL-32 00530374
Sound level meter1
(noise logger)
Rion NL-32 01182950
Note 1: All sound level meters were calibrated before and after measurement periods and no significant drift in calibration was found to have occurred. The results of the measurements are therefore considered to be representative.
Weather Conditions: The observed weather conditions were acceptable for acoustic measurement throughout the
attended survey periods (low-medium wind speeds and no rain). Weather records for the area
confirmed that weather conditions were also generally acceptable for acoustic measurement during
the unattended monitoring.
Measurement
Positions:
Position (refer plan below)
Description
N1 Attended noise monitoring position. 1.5m above local ground level. Free-field. Direct line of sight to West Green Road.
L1 Unattended noise logging position. Approximately 3.5m above local ground level. Free-field. Direct line of sight to West Green Road.
L2 Unattended noise logging position. Approximately 3.5m above local ground level. Free-field. Direct line of sight to West Green Road.
Site Plan showing
Measurement
Positions:
Attended Noise
Monitoring Results:
Date Position Time Meas.
Length
LAeq,
dB
LAmax,
dB
LA90,
dB
Observations
18.11.14 N1 15:25 9 secs - 79 - Maximum noise measurement of bus passby on
West Green Road
15:29 7 secs - 78 - Maximum noise measurement of bus passby on
West Green Road
15:34 8 secs - 80 - Maximum noise measurement of bus passby on
West Green Road
15:35 7 secs - 79 - Maximum noise measurement of bus passby on
West Green Road
15:22 5 secs - 75 - Maximum noise measurement of car passby on
West Green Road
15:24 11 secs - 76 - Maximum noise measurement of car passby on
West Green Road
15:28 8 secs - 76 - Maximum noise measurement of car passby on
West Green Road
15:30 8 secs - 75 - Maximum noise measurement of car passby on
West Green Road
15:34 6 secs - 79 - Maximum noise measurement of car passby on
West Green Road
15:22 5 secs - 78 - Maximum noise measurement of van passby on
West Green Road
N1
L1
Site
L2
Unattended Noise
Monitoring Summary:
Meas. Period Position Daytime (0700-2300hrs) Night-time (2300-0700hrs)
LAeq,16hr,
dB
LA90,1hr dB1 LAeq,8hr,
dB
LA90,5mins,
dB1
LAmax, dB2
18.11.14 to 19.11.14 L1 67 55 58 37 80
18.11.14 to 19.11.14 L2 64 55 57 47 75
Note 1: Most frequent typical background noise level measured during the period shown.
Note 2: Highest typical maximum noise level during the night-time (not exceeded more than 10-15 times per night).
Unattended Noise
Monitoring Graphs:
Meas. Period Position
18.11.14 to 19.11.14 L1