Dover Court
Proposed Ball Court
Noise Impact Assessment
On behalf of Islington Council
Project Ref: 29930 | Rev: 01 | Date: April 2014
Office Address: Caversham Bridge House, Waterman Place, Reading, Berkshire RG1 8DN
T: +44 (0)118 950 0761 F: +44 (0)118 959 7498 E: [email protected]
Dover Court, Proposed Ball Court
Noise Impact Assessment
Contents
1 Introduction ................................................................................................................................. 1 2 Guidance Documents ................................................................................................................. 2 2.1 British Standard 4142:1997 Rating industrial noise, effecting mixed residential and
industrial areas (BS4142) .............................................................................................. 2 2.2 British Standard 8233: 2014 ‘Guidance on Sound Insulation and noise reduction for
buildings’........................................................................................................................ 3 2.3 World Health Organisation (W.H.O.) – Guidelines for Community Noise, 1999 ........... 4 3 Proposed Ball Court Noise Impact Criterion ............................................................................ 6 4 Noise Survey................................................................................................................................ 7 5 4.1 Procedure ...................................................................................................................... 7 4.2 Measurement Position ................................................................................................... 7 4.3 Instrumentation .............................................................................................................. 7 4.4 Results & Discussion of Noise Climate ......................................................................... 8 4.5 Discussion of Noise Climate.......................................................................................... 8 Noise Impact Assessment .......................................................................................................... 9 5.1 Noise impact considering external daytime criteria ....................................................... 9 5.2 Noise impact considering worst case noise impact....................................................... 9 6 Mitigation measures.................................................................................................................. 12 7 Conclusions ............................................................................................................................... 13 Tables
Table 4.1: Instruments Used During Survey …………………………………………………………………5
Table 5.1: Likely future ambient noise levels at centre of gardens at Westcliff house (located to the
north of the proposed ball
court)…………………………………………………….……………………...………..…………10
Table 5.2 Resultant incident noise level change due to relocated ball court…………………………….10
Table 5.3: Subjective response to change in loudness…………………………………………………….11
Appendices
Appendix A: Acoustic Terminology
Appendix B: Figures
Appendix C: Time History Graph
iii
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Noise Impact Assessment
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Noise Impact Assessment
1
Introduction
1.1.1
The redevelopment proposals for the Dover Court Estate in Islington allow for the relocation of
an existing ball court.
1.1.2
Peter Brett Associates has been commissioned to review the likely noise impact at nearby
residential premises from activities in the proposed relocated ball court.
1.1.3
The ball court will be used for recreational use with organized games such as basketball and
football. It will be open to the public and floodlights will be provided.
1.1.4
There is currently no relevant guidance which describes a methodology to assess the noise
impact from activities in a ball court.
1.1.5
The advice within BS4142, BS8233 and the World Health Organization guidelines are often
cited in similar assessments. The relevant sections from these documents are described
briefly in Section 2 alongside a short discussion about their appropriateness and limitations.
1.1.6
A glossary of acoustic terms is included within Appendix A
The remaining of the report is structured as follows:
Section 2 presents a description of guidance documents
Section 3 presents the proposed ball court noise impact criterion
Section 4 presents the methodology and results of a noise survey
Section 5 presents the noise impact assessment
Section 6 presents the proposed mitigation measures and
Section 7 presents the conclusions
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Noise Impact Assessment
2
Guidance Documents
2.1
British Standard 4142:1997 Rating industrial noise, effecting mixed
residential and industrial areas (BS4142)
2.1.1
BS 4142 describes a method of determining the level of noise of an industrial nature together
with procedures for assessment as to whether the noise in question is likely to give rise to
complaints from people living nearby.
2.1.2
Section 1 of BS 4142 defines the scope of noise sources to which the rating methodology of
the Standard may be applied: “…noise levels from factories, or industrial premises, or fixed
installations, or sources of an industrial nature in commercial premises”.
2.1.3
The Standard states that, “…it is intended to be used for assessing the measured or
calculated noise levels from both existing premises and new or modified premises. The
standard may be helpful in certain aspects of environmental planning and may be used in
conjunction with recommendations on noise levels and methods of measurement published
elsewhere”.
2.1.4
The procedure contained in BS 4142 for assessing the likelihood of complaints is to compare
the noise level of the industrial process with the ‘background’ noise level. The noise from the
industrial process is referred to as the ‘specific’ noise level, and is either measured or
predicted at the assessment location(s) which is usually outside a nearby noise sensitive
receptor.
2.1.5
Where the noise contains a “distinguishable discrete continuous note (whine, hiss, screech,
hum etc.) or if there are distinct impulses in the noise (bangs, clicks, clatters or thumps), or if
the noise is irregular enough to attract attention” then a correction of +5 dB is added to the
specific noise level to obtain the ‘rating level’ or LAr.
2.1.6
The likelihood of noise provoking complaints is assessed by subtracting the background noise
level from the rating noise level. The Standard states that:
“A difference of around 10 dB or higher indicates that complaints are likely. A difference of
around 5dB is of marginal significance. A difference of -10 dB is a positive indication that
complaints are unlikely.”
2.1.7
2.1.8
It is worth noting that the Standard provides advice on the limits of the applicability of the
rating method. Specifically:

The quantified assessment of community or individual annoyance is beyond the scope of
the standard.

The assessment of nuisance is beyond the scope of the standard.

The standard only applies to noise from factories, or industrial premises, or fixed
installations, or sources of an industrial nature in commercial premises.

The method does not apply to assessing noise inside buildings.

The method does not apply to assessing noise in situations where the background and
rating noise level are very low (i.e. LA90 below 30 dB and LAr,T below 35 dB).
BS4142 is currently undergoing an overhaul and a draft version has been published for
consultation. The draft version should not be considered as a British Standard and it is not
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current beyond 30 April 2014. However, it has undergone a lengthy consultation process and
may be considered as emerging guidance.
2.1.9
The scope of the draft BS4142 reiterates its application for industrial and commercial sources
and now specifically excludes the measurement and rating of sound levels from the following
sources:
i) vehicle traffic on the public highway;
ii) aircraft in flight;
iii) passing trains and trams, etc;
iv) boats on open seas;
v) recreational activities, including all forms of motorsport;
vi) mineral extraction;
vii) wind farms;
viii) music and other entertainment events and venues;
ix) shooting grounds;
x) construction and demolition;
xi) animals;
xii) people; and
xiii) public address systems.
2.2
British Standard 8233: 2014 ‘Guidance on Sound Insulation and noise
reduction for buildings’
2.2.1
BS 8233, in relation to this planning application, sets out desirable guideline values in
habitable rooms, such as living rooms and bedrooms.
2.2.2
The guideline values relate to steady external noise without a specific character, previously
termed ‘anonymous noise’. According to the standard, noise has a specific character if it
contains features such as a distinguishable, discrete and continuous tone, is irregular enough
to attract attention, or has strong low-frequency content, in which case lower noise limits might
be appropriate. Examples of noise with a character may include tonal/intermittent plant noise
emissions, music playback, and workshop noise. Examples of external steady noise sources
may include environmental noise sources such as motorways with busy road traffic flows.
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2.2.3
The desirable internal ambient noise levels for dwellings are presented in Table 2.2.
Table 2.2: BS 8233 Recommended Internal Ambient Noise Levels for Dwellings
Activity
Location
07:00 to 23:00
23:00 to 07:00
Resting
Living room
35 dB LAeq, 16hour
-
Dining
Dining room/area
40 dB LAeq, 16hour
-
Bedroom
35 dB LAeq, 16hour
30 dB LAeq, 8hour
Sleeping (daytime
resting)
Note 4
Regular individual noise events (for example, scheduled aircraft or passing trains) can cause sleep
disturbance. A guideline value may be set in terms of SEL or LAmax, f, depending on the character and
number of events per night. Sporadic noise events could require separate values.
Note 5
If relying on closed windows to meet the guide values, there needs to be an appropriate alternative
ventilation that does not compromise the façade insulation or the resulting noise levels.
Note 7
Where development is considered necessary or desirable, despite external noise levels above WHO
guidelines, the internal target levels may be relaxed by up to 5 dB and reasonable internal conditions still
achieved.
2.2.4
The standard also provides advice in relation to design criteria for external noise. It states that
“for traditional external areas that are used for amenity space, such as gardens and patios, it
is desirable that the external noise level does not exceed 50 dB LAeq,T, with an upper guideline
value of 55 dB LAeq,T which would be acceptable in noisier environments. However, it is also
recognized that these guideline values are not achievable in all circumstances where
development might be desirable. In higher noise areas, such as city centres or urban areas
adjoining the strategic transport network, a compromise between elevated noise levels and
other factors, such as the convenience of living in these locations or making efficient use of
land resources to ensure development needs can be met, might be warranted. In such a
situation, development should be designed to achieve the lowest practicable levels in these
external amenity spaces, but should not be prohibited.
2.2.5
Other locations, such as balconies, roof gardens and terraces, are also important in residential
buildings where normal external amenity space might be limited or not available, i.e. in flats,
apartment blocks, etc. In these locations, specification of noise limits is not necessarily
appropriate. Small balconies may be included for uses such as drying washing or growing pot
plants, and noise limits should not be necessary for these uses.“
2.4.6
However, the general guidance on noise in amenity space is still appropriate for larger
balconies, roof gardens and terraces, which might be intended to be used for relaxation. In
high-noise areas, consideration should be given to protecting these areas by screening or
building design to achieve the lowest practicable levels. Achieving levels of 55 dB LAeq,T or less
might not be possible at the outer edge of these areas, but should be achievable in some
areas of the space.
2.2.7
There is no guidance in BS 8233 for external areas at night.
2.3
World Health Organisation (W.H.O.) – Guidelines for Community Noise,
1999
2.3.1
This document is a review of the medical and scientific knowledge on health impacts of
community noise, and provides guidance to health authorities and professionals dealing with
the effect of noise in non-industrial environments.
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2.3.2
The guidelines states that in order to protect the majority of the people from being seriously
annoyed during the daytime, the outdoor noise levels should not exceed 55 dB LAeq on
balconies, terraces and outdoor living areas. To protect people from being moderately
annoyed during the daytime, the noise level should not exceed 50 dB LAeq.
2.3.3
In section 4.2.1. the guidelines state that:
“For speaker-to-listener distance of about 1 m:
Speech in relaxed conversation is 100% intelligible in background noise levels of about 35
dBA, and can be understood fairly well in background levels of 45 dBA.
Speech with more vocal effort can be understood when the background sound pressure
level is about 65 dBA.”
2.3.4
The World Health Organization guideline noise levels include noise levels due to
“neighbourhood”. This definition may include noise due to sporting activities, playgrounds, ball
courts etc.
2.3.5
It should be noted that the W.H.O. guideline values for dwellings are set in order to prevent
the noise induced onset of “critical health effect”. This means that the limits are at the lowest
noise level that would result in any psychological, physiological or sociological effect and
therefore can be considered to represent the Lowest Observed Adverse Effect level (LOAEL).
2.3.6
A report compiled by the National Physical Laboratory (CD/D50) for the DETR concluded that
the W.H.O. guidelines might be considered as highly precautionary. In considering how the
W.H.O. guidelines should be interpreted, the report states that:
“In essence the W.H.O. guidelines represent a consensus view of international expert
opinion on the lowest threshold noise levels below which the occurrence rates of particular
effects can be assumed to be negligible. Exceedances of the W.H.O. guideline values do
not necessarily imply significant noise impact and indeed, it may be that significant impacts
do not occur until much higher degrees of noise exposure are reached”.
2.3.7
The National Physical Laboratory report (CD/D50) also states:
“The most constructive use for the W.H.O. guidelines will be to set thresholds above which
greater attention should be paid to the various possibilities for noise control action when
planning new developments. It is important to make clear at this point that exceedances do
not necessarily imply an overriding need for noise control, merely that the relative
advantages and disadvantages of noise control action should be weighed in the balance. It
is all a question of balance, and mere exceedance of the W.H.O. guidelines just starts to tip
the scales”.
2.3.8
Finally, the National Physical Laboratory report (CD/D50) notes that:
“We know from the most recent national survey of noise exposure carried out in England
and Wales (SARGENT 93) that around 56% of the population are exposed to daytime
noise levels exceeding 55 dB(A) Leq,16hr” and “In addition there is no evidence that anything
other than a small minority of the population exposed at such noise levels find them to be
particularly onerous in the context of their daily lives”.
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3
Proposed Ball Court Noise Impact Criterion
3.1.1
There are no recognised building standards, codes of practice, typical planning requirements
which propose suitable noise limits (or assessment methodologies) for the noise impact of
activities within a ball court. Therefore in order to derive a suitable criterion a number of
factors must be considered. Points of consideration include the following:
3.1.2

It should be recognised that the use of the ball court facilities will be reduced in the
winter and during cold/rainy days. The use of the ball court would also be reduced
during the school term.

Residents in the surrounding dwellings may use the proposed ball court.

Incident noise levels at the facades/gardens of the nearby residential dwellings already
include noise from the activities in the existing ball court.

Floodlights should be switched off after 21:00 hours in order to reduce ball court activity
into the noise sensitive evening and night-time periods.

As the ball court activities will not be continuous throughout the year, if the external
building fabric of the neighbouring premises is designed to provide a high level of sound
reduction from external noise ingress, there will be acoustic privacy issues when no ball
court activities are taking place. Normal domestic internal activities from the neighbours
will become more distracting as the background noise levels will be too low. Naturally,
this doesn’t occur in detached properties; however, it needs to be seriously considered
in the current terraced residential dwellings. Therefore, due to the irregularity of the
noise source, setting internal noise criteria is not advisable.

It should be noted that setting an LAmax criterion would be inappropriate due to the
daytime use.

A criterion using a shorter time base would be inappropriate due to the variable use of a
ball court throughout the day.

The application of some kind of noise penalty to any noise emanating from the ball court
would be inappropriate as the existing residents are already subject to noise from ball
court activities.

The current open area has the potential to be used by members of the public for various
activities which may generate noise.
Therefore based on the guidance documents in Section 2.0 and the above considerations, it is
recommended that the incident noise levels near the centre of the gardens of residential
premises which are located near the proposed ball court should not exceed a level of 55 dB
LAeq (16hours) during the daytime.
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4
Noise Survey
4.1
Procedure
4.1.1
Fully automated environmental noise monitoring was undertaken from approximately 16:30
hours on Friday 14 March 2014 to 12:30 hours on Monday 17 March 2014.
4.1.2
Due to the nature of the survey, i.e. unmanned, it is not possible to accurately comment on the
weather conditions throughout the entire survey period. However at the beginning and end of
the survey period the wind conditions were calm. The sky was generally clear. We understand
that generally throughout the survey period the weather conditions were similar to this. These
conditions are considered suitable for obtaining representative measurement results.
4.1.3
Measurements were taken continuously of the A-weighted (dBA) L10, L90, Leq and Lmax sound
pressure levels over 1 minute periods.
4.2
Measurement Position
4.2.1
The noise level measurements were undertaken at a single position (Position 1). The sound
level meter was located in 15 Greenhills Terrace overlooking the proposed location of the ball
court. The microphone was attached to a pole, protruding through a partially opened window
and was located approximately 1.5 m from the façade of the building at a height of
approximately 3 m above ground level. The nearest reflecting surfaces to the north, east and
south include neighbouring buildings at over 10 m distance. In order to derive free field noise
levels a correction of 2.5 dB has been applied.
4.2.2
The dominant noise source around the site was distant traffic noise.
4.2.3
The measurement position was selected in order to measure the typical incident noise levels
around the proposed ball court area.
4.3
Instrumentation
4.3.1
The instrumentation used during the survey is presented in Table 4.1 below:
Table 4.1: Instrumentation Used During Survey
Description
Manufacturer
Type
Serial Number
Type 1
Data Logging
Sound Level Meter
Brüel & Kjær
2250
2626232
Type 1 Calibrator
Brüel & Kjær
Latest Verification
LD Calibration on
22/01/14
LD Calibration on
4231
2619375
22/01/14
4.3.2
The sound level meter, including the extension cable, was calibrated prior to and on
completion of the survey. No significant change was found to have occurred (no more than
0.5 dB).
4.3.3
The sound level meter was located in an environmental case with the microphone connected
to the sound level meter via an extension cable. The microphone was fitted with a Brüel &
Kjær windshield.
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4.4
Results & Discussion of Noise Climate
4.4.1
The free field equivalent results of the survey have been plotted on Time History Graph
29930/TH1 enclosed in Appendix C, presenting the 1 minute A-weighted (dBA) Leq and Lmax
levels at the measurement position throughout the duration of the survey.
4.5
Discussion of Noise Climate
4.5.1
Due to the nature of the survey, i.e. unmanned, it is not possible to accurately describe the
dominant noise sources, or specific noise events throughout the entire survey period.
However at the beginning and end of the survey period the main noise sources were distant
traffic noise and that of overhead aircraft. The main use of the open space (where the
proposed ball court will be located was for exercising of dogs). It should be noted that during
our three site visits we did not observe any activities within the existing ball court even though
the weather conditions were favourable for outdoor activities.
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5
Noise Impact Assessment
5.1
Noise impact considering external daytime criteria
5.1.1
Based on the results of similar surveys, the organised activities in ball courts can generate a
sound pressure level of around 60 dB LAeq,(1hour) at the boundary of the court. The noise
associated with ball court activity comprises shouts of players and noise produced by the ball
(i.e. hitting the ground or be kicked). This noise level can be considered to be relatively
consistent across the ball court. It should be noted that noise levels due to activities in play
areas and unsupervised playgrounds can be considerably higher.
5.1.2
The distances from the receiver windows vary from the closest to the furthest edges of the
playground. These distances will have an effect on noise emission.
5.1.3
Due to the close proximity of the nearby residential premises we have modelled the noise
impact of the proposed ball court using two point sources. It should be noted that this is an
approximate calculation.
5.1.4
The attached Figures 1 and 2 show the output from the noise map model used in our
predictions. The incident free field noise levels at 1.5 m from ground level are numerically
shown at the facades of the nearby buildings. The ball court related noise levels presented in
the figures are presented in terms of LAeq (1hour).
5.1.5
Tables 5.1 below present the results of our assessment. The nearest affected gardens belong
to the 6 terraced dwellings in Westcliff house to the north of the ball court.
Table 5.1 Likely future ambient noise levels at centre of gardens at Westcliff house (located to the north of the proposed ball
court)
Predicted likely worst case dB LAeq 16
hour noise impact from ball court
activities
Receptor: Gardens of Westcliff house
(located to the North of the ball court)
Ball court use
5 hours of use
Before relocation
38
After relocation
45
10 hours of use
41
48
Existing
ambient
noise
levels*
48 48 Resultant level,
dB LAeq 16
hour
50 51 *lowest Leq (16 hour) recorded during the survey on Sunday 16 March 2014.
5.2
Noise impact considering worst case noise impact
5.2.1
A worst case assessment would compare the likely predicted change in noise levels due to
the proposed relocation of the ball court whilst considering a busy organized game played at
the quietest time of the day (i.e. before 9:00 hours).
5.2.2
This assessment would therefore consider the incident noise levels at nearby residential
receptors based on the predictions which are shown in the attached noise contours. The
results of the assessment are shown in Table 5.2 below.
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Table 5.2 Resultant incident noise level change due to relocated ball court
Predicted likely noise impact due to ball court relocation
Worst case noise
Worst case noise
impact from ball
impact from ball
Existing lowest Resultant incident
court to residential
court to residential
ambient noise
noise level change
receptor before
receptor after
level (Leq 1
due to relocated
relocation (Leq 1
relocation (Leq 1
hour)
ball court
hour)
hour)
51
42 ‐6 57 54
57
53
58 59 58 56 50 51 50 52 51 50 46 44 43 42 42 42 42 42 42 42 42 3 5 7 7 6 3 5 5 5.2.3
Therefore, based on the results of the above worst case assessment incident noise levels due
to ball court activities will reduce at certain properties and will increase at others. The likely
increase can reach around 7 dB.
5.2.4
In terms of the subjective interpretations of the increases in noise levels, there are variations in
individual perception of the strength of sound and studies have shown that in general
broadband and continuous sound is perceived twice as loud if the sound level increases by 10
dB. Similarly, a 20 dB increase in the sound level is perceived as four times as loud. The
following table provides a subjective interpretation of changes in loudness in typical (i.e. non
laboratory conditions).
Table 5.3: Subjective response to change in loudness
5.2.5
Subjective Response
Change in Noise Level (dB)
Insignificant
1
Just perceptible
3
Clearly noticeable
5
Twice or half as loud
10
Significant
15
Much louder or quieter, four time as loud
20
It should be highlighted that the above table refers to continuous and broadband type sounds
and should not therefore be applied to noise associated with activities in a ball court.
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5.2.6
BS8233 states that “if partially open windows were relied upon for background ventilation, the
insulation would be reduced to approximately 15 dB”. Therefore, if a window is open the
incident noise levels will be reduced by approximately 15dB. If the windows are closed, and
assuming poor quality single glazing windows, then incident noise levels will be around 25dB
lower inside the room.
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6
Mitigation measures
6.1.1
Based on the results of the noise impact assessment it appears that the predicted likely noise
levels in the garden areas overlooking the proposed ball court to the north should comply with
the proposed criterion and therefore no further mitigation measures are proposed.
6.1.2
However, it should be under the discretion of the developer on whether they wish to enhance
the acoustic properties of the garden fences (i.e. by installing acoustic doors without any air
gaps).
6.1.3
It should be noted that ball court activities will be noticeable at the nearby residential dwellings
however, not to a level that could be considered significant.
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7
Conclusions
7.1.1
As part of the redevelopment proposals at Dover Court Estate in Islington, an existing ball
court is proposed to be relocated.
7.1.2
A review of the likely noise impact at the future nearby residential premises has been
undertaken.
7.1.3
A suitable noise criterion at the nearby gardens has been proposed based on the advice in
various relevant documents.
7.1.4
A detailed 72-hour daytime and night-time fully automated noise survey has been undertaken
in order to establish the currently prevailing noise climate at the nearby residential premises.
7.1.5
The assessment has shown that the likely impact should be considered acceptable.
7.1.6
Even though the ball court activities will be noticeable at the nearby residential dwellings, this
will not be at a level that is considered significant.
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Appendix A
Acoustic Terminology
A.1.1
Noise is defined as unwanted sound. The human ear is able to respond to sound in the
frequency range 18 Hz (deep bass) to 18,000 Hz (high treble) and over the audible range of 0
dB (the threshold of perception) to 140 dB (the onset of pain). The ear does not respond
equally to different frequencies of the same magnitude, but is more responsive to midfrequencies than to lower or higher frequencies. To quantify noise in a manner that
approximates the response of the human ear, a weighting (filtering) mechanism is used. This
reduces the importance of lower and higher frequencies, approximating the response of the
human ear.
A.1.2
Furthermore, the perception of noise may be determined by a number of other factors, which
may not necessarily be acoustic. Noise can be perceived to be louder or more noticeable if the
source of the noise is observed; e.g. roads, trains, factories, building sites etc. In general, the
impact of noise depends upon its level, the margin by which it exceeds the background level,
its character and its variation over a given period of time. In some cases, the time of day and
other acoustic features such as tonality may be important, as may the disposition of the
affected individual. Any assessment of noise should give due consideration to all of these
factors when assessing the significance of a noise source. Various noise indices have been
derived to describe the fluctuation of noise levels that vary over time. Usually, these noise
indices relate to specific types of noise, and as such different noise indices are used to
describe road traffic noise, background noise, construction noise, etc.
A.1.3
The weighting mechanism that best corresponds to the response of the human ear is the ‘A’weighting scale. This is widely used for environmental noise measurement and the levels are
denoted as dB(A) or LAeq, LA10,etc, according to the parameter being measured.
A.1.4
Noise is measured on the decibel scale, which is logarithmic rather than linear. As a result of
this, a 3 dB increase in sound level represents a doubling of the sound energy present.
Judgement of sound is subjective, but as a general guide a 10 dB(A) increase can be taken to
represent a doubling of loudness, whilst an increase in the order of 3 dB(A) is generally
regarded as the minimum difference needed to perceive a change. Table A.1 sets out
examples of noise levels typically experienced during everyday activities.
Table A.1: Typical sound levels found in the environment
Sound Level (dB(A))
Location
0 to 10
Threshold of hearing
10 to 20
Broadcasting studio
20 to 30
Quiet bedroom at night
30 to 40
Living room during the day
40 to 50
Typical office
50 to 60
Inside a car
60 to 70
Typical high street
70 to 90
Inside a factory or noisy pub
100 to 110
Burglar Alarm at 1m
110 to 130
Pneumatic drill at 1m away
140
Threshold of Pain
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Noise Impact Assessment
Table A.2 Terminology relating to noise
Parameter
Description
Sound Pressure
Sound, or sound pressure, is a fluctuation in air pressure over the static ambient
pressure.
Sound Pressure Level
(Sound Level)
The sound level is the sound pressure relative to a standard reference pressure
of 20Pa (20x10-6 Pascals) on a decibel scale.
Daytime
The period 07:00-23:00 hours
Decibel (dB)
A scale for comparing the ratios of two quantities, including sound pressure and
sound power. The difference in level between two sounds s1 and s2 is given by
20 log10 (s1/s2). The decibel can also be used to measure absolute quantities by
specifying a reference value that fixes one point on the scale. For sound
pressure, the reference value is 20Pa.
A-weighting, dB(A)
The unit of sound level, weighted according to the A-scale, which takes into
account the increased sensitivity of the human ear at some frequencies.
Noise Level Indices
Noise levels usually fluctuate over time, so it is often necessary to consider an
average or statistical noise level. This can be done in several ways, so a number
of different noise indices have been defined, according to how the averaging or
statistics are carried out.
LAE or SEL
A noise level which, if maintained for a period of 1 second, would cause the
same A-weighted sound energy to be received as is actually received from a
given noise event.
Lw
The Lw, or sound power level, is a measure of the total noise energy of a source.
LAeq,T
A noise level index called the equivalent continuous noise level over the time
period T. This is the level of a notional steady sound that would contain the
same amount of sound energy as the actual, possibly fluctuating, sound that was
recorded.
Lmax,T
A noise level index defined as the maximum noise level during the period T. Lmax
is sometimes used for the assessment of occasional loud noises, which may
have little effect on the overall Leq noise level but will still affect the noise
environment. Unless described otherwise, it is measured using the 'fast' sound
level meter response.
L90,T or Background
Noise Level
A noise level index. The noise level exceeded for 90% of the time over the
period T. L90 can be considered to be the "average minimum" noise level and is
often used to describe the background noise.
L10,T
A noise level index. The noise level exceeded for 10% of the time over the
period T. L10 can be considered to be the "average maximum" noise level.
Generally used to describe road traffic noise.
Free-field
Far from the presence of sound reflecting objects (except the ground), usually
taken to mean at least 3.5 metres
Façade
At a distance of 1 metre in front of a large sound reflecting object such as a
building façade.
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Dover Court, Proposed Ball Court
Noise Impact Assessment
Parameter
Fast Time Weighting
Description
An averaging time used in sound level meters. Defined in BS5969.
Pink Noise
Filtered white noise whereby energy is inversely proportional to frequency
(10log(1/f), where f is frequency). It is commonly used as a sound source in
acoustic testing
Rw
Weighted sound reduction index - single number quantity which characterizes
the airborne sound insulating properties of a material or building element in a
stated frequency band. “C” is a spectrum adjustment to the value of Rw which
takes account of particular sound spectra (predominantly jet aircraft at short
distance, motorway traffic and high speed railway traffic).
Night-time
The period 23:00-07:00 hours
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Dover Court, Proposed Ball Court
Noise Impact Assessment
Appendix B
Figures
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17
Title
Client :
Offices throughout the UK, continental
Europe and Asia
www.peterbrett.com
Caversham Bridge House,
Waterman Place,
Berkshire,
RG1 8DN
Peter Brett Associates LLP
T: +44 (0)118 950 0761
F: +44 (0)118 959 7498
E: [email protected]
Islington Council
Existing Ball Court
Date :
25/03/2014
Scale :
N.T.S
Drawn By:
JLJ
Checked By:
TC
Figure Number:
01
Client :
Title
Offices throughout the UK, continental
Europe and Asia
www.peterbrett.com
Caversham Bridge House,
Waterman Place,
Berkshire,
RG1 8DN
Peter Brett Associates LLP
T: +44 (0)118 950 0761
F: +44 (0)118 959 7498
E: [email protected]
Islington Council
Planned
Date :
25/03/2014
Scale :
N.T.S
Drawn By:
JLJ
Checked By:
TC
Figure Number:
02
Dover Court, Proposed Ball Court
Noise Impact Assessment
Appendix C
Time History Graph
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18
Dover Court Estate, Islington
LAeq and LAmax Noise Levels (1 minute)
Friday 14/04/14 - Monday 17/04/14
90
80
70
Sound Level dB(A)
60
50
LAmax
40
LAeq
30
20
10
0
16:17:32
22:07:32
03:57:32
09:47:32
15:37:32
21:27:32
03:17:32
09:07:32
14:57:32
20:47:32
02:37:32
08:27:32
Time-Hrs
Time History Graph 29930/TH1