Chapter 14 Noise.pptx

• Virtually all development projects have noise
impacts.
• Noise during construction may be due to land
clearance, piling, and the transport of materials
to and from the site.
• Demolition is a further cause of noise.
• As a result, despite the fact that regulations do
not always require noise to be analyzed, the
EIAs for most projects do consider noise.
Introduction

• Noise is a major and growing form of pollution.
• It can interfere with;
• communication,
• increase stress and annoyance,
• cause anger, and
• disturb sleep,
• Lead to lack of concentration, irritability and reduced efficiency.
• It can contribute to stress-related health problems such as high blood pressure.
• Prolonged exposure to high noise levels can cause deafness or partial hearing loss.
• Noise can also affect property values and community atmosphere.
• In Europe, 57 million people are annoyed by road traffic noise, 42 per cent of them seriously; and
the social costs of traffic noise in Europe amount to at least a 40 billion € per year (CE Delft 2007).
Introduction

• Although most EIAs are limited to the impact of
noise on people, noise may also affect animals.
• Although noise is linked to vibration, we deal only
with noise.
• It should be noted, however, that for some
studies like major railway projects and/or projects
involving substantial demolition or piling,
vibration effects can be significant and a full
vibration assessment must be carried out.
Introduction

Definitions
• Noise is unwanted sound.
• It is the annoyance caused by noise that is
important in EIA.
• Noise impact assessment revolves around the
concept of quantifying and “objectifying”
people’s personal responses.
• Sound consists of pressure variations detectable
by the human ear.
• These pressure variations have two
characteristics, frequency and amplitude.
• Sound frequency refers to how quickly the air
vibrates, or how close the sound waves are to
each other (in cycles per second, or Hertz (Hz)).

• For example;
• the sound from a transformer has a wavelength of about
3.5 m, and buzzes at a frequency of 100 Hz;
• a television line emits waves of about 0.03 m, and whistles
at about 10,000 Hz or 10 kHz.
• The lowest frequency audible to humans is 18 Hz, and
the highest is 18,000 Hz.
• Sound amplitude refers to the amount of pressure
exerted by the air, which is often pictured as the height
of the sound waves.
• Amplitude is described in units of pressure per unit
area, microPascals (μPa).
• The amplitude is sometimes converted to sound
power, in picowatts (10−12 watts), or sound intensity
(in 10−12 watts/m2).
Definitions

• As a result, a logarithmic scale of decibels (dB) is used.
• A sound level in decibels is given by
• where P is the amplitude of pressure fluctuations, and p is
20μPa, which is considered to be the lowest audible sound.
• The sound level can also be described as
• where I is the sound intensity and i is 10−12 watts/m2, or by
• where W is the sound power, and w is 10−12 watts.
• The range of audible sound is generally from 0dB to 140dB,
as is shown in Table 4.1.
Definitions

• Because of the logarithmic nature of the decibel
scale;
• a doubling of the power or intensity of a sound, for
instance adding up two identical sounds, generally
leads to an increase of 3dB, not a doubling of the
decibel rating.
• For example two mowing machines, each at 60dB,
together produce 63dB.
• Multiplying the sound power by ten (e.g. ten
mowing machines) leads to an increase of 10dB.
• Figure 4.1 shows how the dB increase can be
calculated if one noise source is added to another.
• Box 4.1 shows two examples of these principles.
Definitions

• Noise levels are rarely steady: they rise and fall with the types of
activity.
• Time-varying noise levels can be described in a number of ways.
• The principal measurement index for environmental noise is the
equivalent continuous noise level, LAeq.
• The LAeq is a notional steady noise level, which is calculated by
averaging all of the sound pressure/power/intensity
measurements, and converting that average into the dB scale.
• Most environmental noise meters read this index directly.
• LAeq has the dual advantages that it: takes into account both the
energy and duration of noise events.
Definitions

Factors influencing noise impacts
• The principal physical factors are the level of the sound being assessed.
• For instance, people in rural environments would expect lower sound levels than
those in a busy city center.
• The level of sound being assessed is determined by several factors.
• 1-First, as one gets further away from a source of sound in the environment, the
level of noise from the source decreases.
• The principal factor contributing to this is probably geometric dispersion of energy.
• As one gets further away from a sound source, the sound power from the source is spread
over a larger and larger area.

• 2-The next most important factor in governing
noise levels is whether the propagation path from
the noise source to the receiver is obstructed.
• If there is a large building, a substantial wall or fence,
this can reduce noise levels by 5–15dB(A).
• The amount of attenuation (reduction) depends upon
the geometry of the situation and the frequency
characteristics of the noise source.
• If the sound is travelling over a reasonable distance,
the type of ground over which it is passing can have a
substantial reduction on the noise level at the
receiver.
• If the sound is passing at a reasonably low physical
level over soft ground (grassland, crops, trees, etc.)
there will be an additional attenuation to that due to
geometric dispersion.

• 3-Meteorological effects generally only need
to be considered where calculations are being
made over large distances (upwards of 100 m
or so).
• Wind speed and direction can affect noise levels.
• Clearly, as distances increase from a noise source,
the noise levels rapidly diminishes.
• Where large distances are involved, and noise level
estimates are critical, it is essential that the noise
predictions need to be clearly defined.

Legislative background and interest
groups

• Noise is controlled in three ways: by
• 1-controlling overall noise levels,
• 2-setting limits on the emission of noise, and
• 3-keeping people and noise apart.
• The local authority environmental health officer’s opinion will be needed by the planning
authority.
• The Environmental Noise Directive requires European Member States to map noise in densely
populated areas and from major transport projects.
• The World Health Organization (WHO 1999) has also defined guideline levels for community
noise (Table 4.3).
• Further legislation and guidance applies to specific types of developments: the key ones are
reviewed at Table 4.4.
Legislative background and interest
groups

• The EIA scoping stage identifies;
• 1-relevant potential noise sources,
• 2-the people and resources likely to be affected by the
proposed project’s noise, and
• 3-noise monitoring locations.
• The baseline studies involve;
• 1-identifying existing information on noise levels,
• 2-carrying out additional noise measurements at
appropriate locations where necessary, and
• 3-considering future changes in baseline conditions.
• The project details should be analyzed and each
potential source of noise impact should be identified.
• Both on-site and off-site sources should be considered
during both the construction and operational stages.
Scoping and baseline studies

• Ultimately the effects of noise are dictated by the
characteristics of the potentially affected receptors.
• Various maps can help to identify noise receptors in the
area.
• The people affected by a Project are not only local
residents but also people working nearby.
• EIAs should identify any potentially particularly noise-
sensitive receivers such as schools, hospitals etc.
• Sites for monitoring are normally determined in
consultation with the environmental health officer and
with the local community.
• However where there are many receivers, for instance
along a proposed road or rail line, representative
receivers will need to be identified.

• A systematic approach is required, splitting potentially
affected receivers into;
• residential,
• non-residential and noise sensitive, and
• non-residential and not noise sensitive.
• It is advisable, however, to treat residential receivers
uniformly.
• Because noise is primarily a local impact, only limited
existing information can be obtained from desktop
studies.
• Information about the wider area may be gathered from
the strategic noise maps.

• Measurement of ambient noise is measured at the
potentially most affected noise-sensitive receptors.
• Every effort should be made to carry out
measurements at the times when the new source will
be operating with typical ambient conditions.
• The noise survey may also record the quietest
conditions which typically occur in an area (e.g. on a
quiet Sunday morning).
• This is because the biggest increase in noise caused by
a proposed development will be in comparison with
these quiet conditions.

• Sound measuring equipment is portable and
battery-powered
• A typical survey strategy may include a limited
number of positions where;
• long-term (24 hours or more) unattended
measurement positions are carried out, and
• plus several positions where shorter term (15
minutes or more) attended sample
measurements are carried out.

• Broadly, noise measurements involve:
• taking note of the equipment type used;
• taking note of the date, weather conditions, wind
speed, and wind direction;
• calibrating the sound meter and microphone;
• setting up the microphone at the appropriate site;
• noting the precise location;
• taking measurements using the criteria from the
relevant guidelines;
• noting start and finish times,
• checking the calibrations.

• A final stage of scoping and baseline studies
is to consider whether baseline noise levels
are likely to change in the future in the
absence of the proposed development.
• For instance, if a development is proposed
near an industrial complex that is currently
under construction, then the future baseline
is likely to change.
• In some cases the future baseline may be
established through calculations.

• The aim of noise prediction in EIA is to identify the
changes in noise levels which may occur, both in the
short and long terms, as a result of a project.
• Predicting noise levels is a complex process which
incorporates a wide range of variables, including:
• existing and possible future baseline noise levels;
• the type of equipment used;
• the time of day when the equipment is used;
• the actions of the site operator;
• the location of the receivers and their sensitivity to noise;
• the topography of the area, including the main forms of
land use and any natural sound barriers;
• meteorological conditions in the area.
• Table 4.6 gives examples of typical sound levels from
construction equipment;
Impact prediction

• Mitigation will be necessary if the noise from the
proposed Project is likely to exceed the levels
recommended in the relevant standards.
• However, it may be useful to implement noise
mitigation measures even if standards are met, to
prevent annoyance and complaints.
• The best noise mitigation includes:
• the siting of machinery and buildings,
• choice of equipment, and
• landscaping to reduce noise
Mitigation

• For a new potentially “noisy” project, mitigation of noise is best carried out at the source.
• Failing this, barriers and the siting of buildings can be used to separate noise sources from
potentially affected noise sensitive locations.
• As a last resort, noise can be controlled at the receiver’s end through the provision of noise
insulation measures.
• Control of noise at the source can take a number of forms.
• 1-First, the equipment used or the modes of operation can be changed to produce less
noise.
• For instance, rotating or impacting machines can be based on anti-vibration mountings.
• Internal combustion engines must be fitted with silencers.
• Traffic can be managed to produce a smooth flow instead of a noisier stop and- start flow, and use of
quieter road surfacing materials can significantly reduce tire noise.
Mitigation

• 2-Second, the source can be sensitively located.
• It can be located (further) away from the receivers, so that noise is reduced over distance.
• A buffer zone of undeveloped land can be left between a noisy development and a residential area.
• The development can be designed so that its noisier components are shielded by quieter components; for
instance housing can be shielded from a factory’s noise by retail units.
• Natural or artificially-constructed topography or landscaping can be used to screen the source.
• The source can be enclosed to insulate or absorb the sound.
Mitigation

• Methods of measuring sound insulation usually distinguish between airborne sound (noise) and structural sound (vibration).
• Broadly, the ability of a panel to resist the transmission of energy from one side of a panel to the other, will depend on
• (a) the mass of the panel (more mass = more transmission loss),
• (b) whether it is layered or not,
• (c) whether it includes sound absorbing material, and
• (d) whether it has any holes or apertures.
Mitigation

• 3-Acoustic fencing or other screens,
either at the source or at the receiver,
can also reduce noise by up to 15dB.
• The effectiveness of screens depends
on
• their height and width (larger is better),
• their location with respect to the source
or receiver (closer is better),
• their form (wrapped around the source
or receiver is better),
• their transmission loss,
• their position with respect to other
reflecting surfaces,
• whether they have any holes or
apertures.
Mitigation

• Control of noise at the receiver’s
end is often similar to that at the
source.
• 1-Good site planning can minimize
the impact of noise;
• 2-A screen can be erected to reflect
sound away from the receiver, for
instance an acoustical screen
between a highway and house.
• 3-The equivalent of a noise
enclosure can be achieved by
soundproofing a house using
double-glazed windows.
Mitigation

Monitoring
• Any noise conditions imposed as part of a project’s planning are enforceable.
• These can apply not only to noise levels (e.g. during construction, operation),
• but also to noise monitoring to be conducted by the developer.
• If no planning conditions are set, local environmental health officers can still monitor
noise from a site,
• for instance in response to local residents’ complaints.
• A best practice EIA could propose not only noise-related planning conditions, but also a
noise monitoring program.
• The sites and noise-measurement techniques used in carrying out baseline noise surveys
should be such that comparable monitoring data can later be collected.

Conclusion
• This has only been a brief introduction to a very technically-complex topic.
• Noise prediction requires expert input, and probably computer models.
• Students are strongly urged to familiarize themselves with the relevant
regulations and standards as well as standard texts on acoustics and noise
control.

Noise EIA Examples
http://www.epd.gov.hk/eia/register/report/eiareport/eia_0392000/theme/0
5.pdf
http://sahra.org.za/sahris/sites/default/files/additionaldocs/Amakhala%20E
moyeni%20WEF%20DEIR%20-%20Appendix%20L%20_NIA_final.pdf
https://hal.archives-ouvertes.fr/hal-00811229/document
http://www.gov.ms/wp-content/uploads/2011/02/Montserrat-Sandmining-
EIA_Dec-2011_PART-TWO-ANNEX.pdf

Chapter 14 Noise.pptx

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