Download unit 5 - noise pollution

UNIT 5 - NOISE POLLUTION
5.1. Sources of noise pollution
5.2. Effects
5.3. Assessment
5.4. Standards
5.5. Control methods
5.6. Prevention
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Sound
• Sound is a vibration that propagates as a
mechanical
wave
of
pressure
and
displacement, through some medium (i.e. air
or water).
• Sound refers to only those vibrations with
frequencies that are within the range of
hearing for human.
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Noise
• Noise is basically any unwanted sound.
• It is measured in dB units.
Sound
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Noise
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Characteristics of Noise
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Sound pressure
Frequency
Duration
Time of the day
Location
Intermittency
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Kinds of Noise
• Continuous
• Variable or Intermittent
• Impulse or Impact
Kinds of noise which affect analysis
• Chemical Noise
• Instrumental Noise
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Variable Noise
Impulse Noise
Continuous Noise
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Instrumental Noise
• Thermal Noise
• Flicker Noise
• Shot Noise
• Environmental Noise
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WHAT IS NOISE POLLUTION?
 Sound that is unwanted or disrupts one’s quality of life
is called as noise. When there is lot of noise in the
environment, it is termed as noise pollution.
 Sound becomes undesirable when it disturbs the
normal activities such as working, sleeping, and during
conversations.
 It is an underrated environmental problem because of
the fact that we can’t see, smell, or taste it.
 World Health Organization stated that “Noise must be
recognized as a major threat to human well-being”
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5.1 Sources of Noise Pollution
• Household Sources
• Social Events
• Commercial and Industrial Activities
• Transportation
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Sources of Noise Pollution
• Transportation systems are the main source of noise
pollution in urban areas.
• Construction of buildings, highways, and streets cause
a lot of noise, due to the usage of air compressors,
bulldozers, loaders, dump trucks, and pavement
breakers.
• Industrial noise also adds to the already unfavorable
state of noise pollution.
• Loud speakers, plumbing, boilers, generators, air
conditioners, fans, and vacuum cleaners add to the
existing noise pollution.
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5.1 Sources of Noise Pollution
•
•
•
•
•
•
•
•
•
•
•
contd…
Household Sources
Food Mixer
Grinder
Vacuum Cleaner
Washing machine and Dryer
Air Conditioner
Straighter and curlers
Cooler
TV
iPods and Earphones
Loud speaker
Neighbor's Barking Dog
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5.1 Sources of Noise Pollution
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5.1 Sources of Noise Pollution
contd…
Social Events
•
•
•
•
Places of Worship
Discos and Gigs
Parties
Markets where people sell goods with
loudspeaker.
When these events are not often, they can be
termed as nuisance rather than noise pollution.
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5.1 Sources of Noise Pollution
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5.1 Sources of Noise Pollution
contd…
Commercial and Industrial Activities
• Printing Presses
• Manufacturing Industries
• Construction Sites
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5.1 Sources of Noise Pollution
contd…
Sources of Construction Noise
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•
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Pneumatic Hammers
Air Compressors
Bulldozers
Loaders
Dump Trucks
Pavement breakers
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5.1 Sources of Noise Pollution
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5.1 Sources of Noise Pollution
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Sources of Industry Noise
• Fans
• Motors
• Compressors mounted outside
This interior noise sources have significant
impacts on industrial workers, among whom noise
induced hearing loss is unfortunately common
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5.1 Sources of Noise Pollution
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5.1 Sources of Noise Pollution
contd…
Transportation
• Road Traffic Noise
• Aircraft Noise
• Noise from Rail Roads
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5.1 Sources of Noise Pollution
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5.1 Sources of Noise Pollution
contd…
Causes of Noise Pollution
• Poor Urban Planning
• Sounds from Motor Vehicles
• Sounds from Musical Instruments
• Car Alarms
• Office Equipment
• Factory Machinery
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5.1 Sources of Noise Pollution
contd…
Causes of Noise Pollution
• Construction Work
• Barking Animals
• Appliances
• Audio Instruments
• Loud Speakers
• Noise Created by People
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Solutions for Noise Pollution
• Planting bushes and trees in and around sound
generating sources is an effective solution for noise
pollution.
• Regular servicing and tuning of automobiles can
effectively reduce the noise pollution.
• Buildings can be designed with suitable noise
absorbing material for the walls, windows, and
ceilings.
• Workers should be provided with equipments such
as ear plugs and earmuffs for hearing protection.
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Solutions for Noise Pollution
• Similar to automobiles, lubrication of the
machinery and servicing should be done to
minimize noise generation.
• Soundproof doors and windows can be installed
to block unwanted noise from outside.
• Regulations should be imposed to restrict the
usage of play loudspeakers in crowded areas and
public places.
• Factories and industries should be located far
from the residential areas.
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Solutions for Noise Pollution
• Community development or urban
management should be done with longterm planning, along with an aim to
reduce noise pollution.
• Social awareness programs should be
taken up to educate the public about the
causes and effects of noise pollution.
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5.2. Effects of Noise Pollution
• Effects on Human
• Effects on Animals
• Effects on Environment
(Vegetation, Property)
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Health Effects
• According to the USEPA, there are direct links
between noise and health. Also, noise pollution
adversely affects the lives of millions of people.
• Noise pollution can damage physiological and
psychological health.
• High blood pressure, stress related illness, sleep
disruption, hearing loss, and productivity loss are
the problems related to noise pollution.
• It can also cause memory loss, severe depression,
and panic attacks.
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5.2. Effects of Noise Pollution
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5.2. Effects of Noise Pollution
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Effects on Human
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Hearing Impairment
Interference with Spoken Communication
Decrease in Efficiency
Lack of Concentration
Fatigue
Sleep Disturbances
Cardiovascular Disturbances
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5.2. Effects of Noise Pollution
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5.2. Effects of Noise Pollution
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• Disturbance in Mental Health
• Impaired Task Performance
• Negative Social Behavior and Annoyance
reactions
• Abortion
• Abnormal Fetus
• Temporary or Permanent
Deafness
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5.2. Effects of Noise Pollution
contd…
Diseases Caused by Noise Pollution
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High Blood Pressure
Heart Attack
Cancer
Asthma
Coughing, wheezing
Deafness
Annoyance
Stress
Anxiety
Reduced lung development
Bronchitis
Insomnia
Arterious Clerosis
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5.2. Effects of Noise Pollution
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5.2. Effects of Noise Pollution
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Effect on Animals
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Damages Nervous system
Altering Prey/predator detection
Creates problems in Navigation
They become Dangerous and Attacking
Raise Metabolism
Reduction of useable Habitat
Death of Certain Species
Genetic and Evolutionary Problems
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5.2. Effects of Noise Pollution
contd…
Continued…..
•
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Hormone imbalance
Chronic Stress
Panic and Escape Behavior
Abandonment of Offspring
Injury
Loudness of Interspecies Communication
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5.2. Effects of Noise Pollution
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Effects on Environment
• Breakage of Earth Barrier
• Poor Quality of Crops
• Damages Buildings, bridges and Monuments
• Weakens the Edifice of Building
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5.2. Effects of Noise Pollution
contd…
Control of Noise Pollution
• Control at Source
• Control in the Transmission Path
• Using Protective Equipment
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5.2. Effects of Noise Pollution
contd…
Control at Source
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Reducing the Noise Levels from Domestic Sectors
Maintenance of Automobiles
Use of Economic instruments
Control over Vibrations
Low Voice Speaking
Prohibition on Usage of loudspeakers
Selection of Machinery
Maintenance of Machines
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5.2. Effects of Noise Pollution
contd…
Control in the Transmission Path
• Installation of Barriers
• Installation of Panels and Enclosures
• Green Belt development
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5.2. Effects of Noise Pollution
contd…
Using Protection Equipment
• Job Rotation
• Exposure Reduction
• Hearing Protection
• Protection at the Receiver End
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5.2. Effects of Noise Pollution
contd…
More Noise Control Techniques
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Sound insulation
Sound Absorption
Vibration Damping
Vibration Isolation
Urban Planning
Public Education and Awareness
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5.3. Noise assessment
•
•
•
•
•
A noise assessment is an examination of
the nature and characteristics of a noise. It
may involve verifying aural factors such as:
The location of the noise source
Its audibility at certain locations
The time the noise is made and its duration
Its characteristics
The reported effect it has on people.
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5.3. Noise assessment
contd…
Definition of offensive noise:
Depending on the type of noise under
consideration, noise can be considered as
offensive in three ways according to its:
• Audibility
• Duration
• Inherently offensive characteristics.
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5.3. Noise assessment
contd…
Duration of noise test for intruder alarms:
• It does not matter whether the alarm sounds
continuously or intermittently.
• For example, a car alarm that sounds for 30 seconds,
stops for 1 minute and then sounds again for another
30 seconds is taken to sound for 60 seconds, which is
more than the 45 seconds prescribed for a vehicle
alarm manufactured on or after 1 September 1997.
• For building intruder alarms, the assessment needs to
be made inside a habitable room in a neighbour’s
residence. For vehicle intruder alarms the assessment
can be made anywhere.
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5.3. Noise assessment
contd…
• The times of use or duration of the noise
automatically make the noise offensive.
• In other cases it will be necessary to consider a
range of factors to determine whether the noise
is offensive, including the following:
1. The loudness of the noise, especially compared with
other noise in the area
2. The character of the noise
3. The time and duration of the noise
4. Whether the noise is typical for the area
5. How often the noise occurs
6. The number of people affected by the noise.
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5.3. Noise assessment
contd…
Assessing noise with a sound level meter:
• A sound level meter should be used to measure
noise levels when:
• Determining an acceptable noise level for
inclusion in a planning approval or a Noise
Control Notice or Prevention Notice
• Testing whether a particular noise complies
with a level prescribed in a planning approval or
notice
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5.3. Noise assessment
contd…
• Gathering evidence to support an offensive
noise test, such as:
– quantifying how loud the noise is
– assessing how loud it is relative to the
background noise (see subsection 2.2.1
‘Intrusive noise’, below)
– determining the presence of annoying
characteristics such as tones supporting a
prosecution or disputed Penalty Notice.
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5.3. Noise assessment
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5.3. Noise assessment
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5.3. Noise assessment
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Intrusive noise
• Noise is identified as ‘intrusive’ if it is
noticeably louder than the background noise
and considered likely to disturb or interfere
with those who can hear it.
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5.3. Noise assessment
contd…
Measuring noise
Noise measurements should be undertaken
by officers properly trained to use noise
equipment.
• If you are inexperienced with noise
measurements, it is desirable that you get to
know what typical decibel levels sound like.
• Become familiar with the sound level meter and
its controls.
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5.3. Noise assessment
contd…
• Decide when the noise is representative of the
worst case level of noise from the source or
activity
being
investigated
and
take
measurements at this time.
• Avoid taking measurements when it is raining or
the average wind speed exceeds 5 metres per
second at microphone height.
• Calibrate the sound level meter before and after
each set of noise measurements
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5.3. Noise assessment
contd…
• Ensure the sound level meter is in the correct position.
• Measure the noise under investigation for long enough
to establish that the measured value is representative
of the subject noise.
• Measure the noise at the location where the impact
occurs.
• When the noise under investigation is affected by
extraneous noise, be sure that the
• subject noise is what you are measuring.
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5.3. Noise assessment
contd…
Sequence of steps for measuring noise
• Before going out to take a measurement, check
that the sound level meter has a current
calibration certificate issued by an accredited
laboratory (for example, NATA).
• Familiarize yourself with the meter and its
settings.
• Select a representative location and time of day
to take measurements, taking into account
information about the subject noise and any
complaints received.
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5.3. Noise assessment
contd…
• Set the microphone at 1.2 to 1.5 metres above
the ground and, where feasible, avoid
measurements within 3 metres of any walls,
buildings and other reflecting surfaces.
• Ensure weather conditions are suitable: no
rain and a wind speed of less than 5 m/s and
note these prevailing conditions in a log book.
• Do a field calibration of the sound level meter
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5.3. Noise assessment
contd…
• Measure the subject noise for a pre-determined
period (such as 15 minutes) and check that the
selected descriptor (for example LAeq) is suitable.
• If there is variation in the source noise level
during the set period of measurement, increase
your confidence in the value being representative
of the worst case by taking a second and perhaps
a third reading for the same period of time.
• If necessary, measure the LA90 background noise
level for the same set period in the absence of
the subject noise.
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5.3. Noise assessment
contd…
• Where noise other than that under consideration
occurs during measurement, take another
reading to avoid the readings being
contaminated.
• At the end of the measurements do another field
calibration of the sound level meter.
• If there is more than a 1 decibel variation
between the calibrated level and the first
calibrated level, the measurements may be
invalid, in which case the measurement
procedure will need to be repeated.
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5.3. Noise assessment
contd…
• Document observations of weather and noise that were heard
during the measurements, including the time of specific
events that may affect readings, such as a frog croaking or a
dog barking.
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Noise rating
Equivalent sound level, Leq :
• It is the constant sound pressure level which would
have produced the same total energy as the actual
sound level over the given time. It is denoted as Leq.
•
•
•
•
•
Leq = equivalent continuous sound pressure level in dB
p0 = reference pressure level (typically 20 µPa)
pA = acquired sound pressure
t1 = start time for measurement
t2 = end time for measurement
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L10, L50 and L90 :
Noise rating
• L10 is the level exceeded for 10% of the time. For 10%
of the time, the sound or noise has a sound pressure
level above L10. For the rest of the time, the sound or
noise has a sound pressure level at or below L10. These
higher sound pressure levels are probably due to
sporadic or intermittent events.
• L50 is the level exceeded for 50% of the time. It is
statistically the mid-point of the noise readings. It
represents the median of the fluctuating noise levels.
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Noise rating
• L90 is the level exceeded for 90% of the time.
For 90% of the time, the noise level is above
this level. It is generally considered to be
representing the background or ambient level
of a noise environment.
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Noise rating
Perceived Noise Levels (PNL)
• The noise of aircraft is described in terms of
Perceived Noise Levels (PNL), a scale of
noisiness, expressed in pNdB.
Ldn
• The day-night equivalent value of sound level.
The day is counted from 6AM to 9PM (15hrs)
and night from 9PM- 6AM (9hrs).
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5.4. Standards of noise pollution
Whereas the increasing ambient noise levels in
public places from various sources, inter-alia,
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
industrial activity,
construction activity,
fire crackers,
sound producing instruments,
generator sets,
loud speakers,
public address systems,
music systems,
vehicular horns and
other mechanical devices
have deleterious effects on human health and the
psychological well being of the people;
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5.4. Standards of noise pollution
contd…
• it is considered necessary to regulate and control
noise producing and generating sources with the
objective of maintaining the ambient air quality
standards in respect of noise
• Whereas a draft of Noise Pollution (Control and
Regulation) Rules, 1999 was published under the
notification of the Government of India in the
Ministry of Environment and Forests vide number
S.O. 528 (E), dated the 28th June, 1999
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5.4. Standards of noise pollution
contd…
1. Ambient air quality standards in respect of
noise for different areas/zones.• The State Government shall categorize the areas
into industrial, commercial, residential or silence
areas / zones for the purpose of implementation
of noise standards for different areas.
•
An area comprising not less than 100 meters
around hospitals, educational institutions and
courts may be declared as silence area / zone for
the purpose of these rules.
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5.4. Standards of noise pollution
contd…
• The State Government shall take measures for
abatement of noise including noise emanating
from
–
–
–
–
–
vehicular movements,
blowing of horns,
bursting of sound emitting firecrackers,
use of loud speakers or public address system and
sound producing instruments
and ensure that the existing noise levels do
not exceed the ambient air quality standards
specified under these rules.
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5.4. Standards of noise pollution
contd…
1. Day time shall mean from 6.00 a.m. to 10.00 p.m.
2. Night time shall mean from 10.00 p.m. to 6.00 a.m.
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5.4. Standards of noise pollution
contd…
• * dB(A) Leq denotes the time weighted average of the
level of sound in decibels on scale A which is relatable
to human hearing.
• A “decibel” is a unit in which noise is measured.
• “A”, in dB(A) Leq, denotes the frequency weighting in
the measurement of noise and corresponds to
frequency response characteristics of the human ear.
• Leq: It is an energy mean of the noise level over a
specified period.
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5.4. Standards of noise pollution
contd…
2. Responsibility as to enforcement of noise
pollution control measures.• The noise levels in any area / zone shall not
exceed the ambient air quality standards in
respect of noise as specified in the Schedule.
• The authority shall be responsible for the
enforcement of noise pollution control
measures and the due compliance of the
ambient air quality standards in respect of
noise.
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5.4. Standards of noise pollution
contd…
3. Restrictions on the use of loud speakers / public
address system and sound producing instruments:
• A loud speaker or a public address system shall not be
used except after obtaining written permission from
the authority.
• A loud speaker or a public address system or any sound
producing instrument or a musical instrument or a
sound amplifier shall not be used at night time except
in closed premises for communication within, like
auditoria, conference rooms, community halls,
banquet halls or during a public emergency.
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5.4. Standards of noise pollution
contd…
• The noise level at the boundary of the public
place, where loudspeaker or public address
system or any other noise source is being used
shall not exceed 10 dB (A) above the ambient
noise standards for the area or 75 dB (A)
whichever is lower;
• The peripheral noise level of a privately owned
sound system or a sound producing instrument
shall not, at the boundary of the private place,
exceed by more than 5 dB (A) the ambient noise
standards specified for the area in which it is
used.
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5.4. Standards of noise pollution
contd…
4. Restrictions on the use of horns, sound emitting
construction equipments and bursting of fire
crackers:• No horn shall be used in silence zones or during night
time in residential areas except during a public
emergency.
• Sound emitting fire crackers shall not be burst in
silence zone or during night time.
• Sound emitting construction equipments shall not be
used or operated during night time in residential areas
and silence zones.
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5.4. Standards of noise pollution
contd…
5. Consequences of any violation in silence zone / area.
Whoever, in any place covered under the silence
zone / area commits any of the following offence, he
shall be liable for penalty under the provisions of the
Act:1. whoever, plays any music or uses any sound amplifiers,
2. whoever, beats a drum or tom-tom or blows a horn
either musical or pressure, or trumpet or beats or
sounds any instrument, or
3. whoever, exhibits any mimetic, musical or other
performances of a nature to attract crowds.
4. whoever, bursts sound emitting fire crackers; or
5. whoever, uses a loud speaker or a public address system.
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6. Noise limits for vehicles at manufacturing stage
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5.5. Control of Noise Pollution
• Noise generation is associated with most of our daily
activities.
• A healthy human ear responds to a very wide range of SPL
from - the threshold of hearing at zero dB, uncomfortable
at 100-120 dB and painful at 130-140 dB(3).
• Due to the various adverse impacts of noise on humans
and environment, noise should be controlled.
• The technique or the combination of techniques to be
employed for noise control depend upon the extent of the
noise reduction required, nature of the equipment used
and the economy aspects of the available techniques.
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5.5. Control of Noise Pollution
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5.5. Control of Noise Pollution
contd…
• Reduction in the noise exposure time or
isolation of species from the sources form part
of the noise control techniques besides
providing personal ear protection, engineered
control for noise reduction at source and/or
diversion in the trajectory of sound waves.
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5.5. Control of Noise Pollution
contd…
Noise Control at Source
The noise pollution can be controlled at the
source of generation itself by employing
techniques like
1. Reducing the noise levels from domestic sectors
2. Maintenance of automobiles
3. Control over vibrations
4. Low voice speaking
5. Prohibition on usage of loud speakers
6. Selection of machinery
7. Maintenance of machines
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5.5. Control of Noise Pollution
contd…
Reducing the noise levels from domestic sectors:
• The domestic noise coming from radio, tape recorders,
television sets, mixers, washing machines, cooking
operations can be minimized by their selective and
judicious operation.
• By usage of carpets or any absorbing material, the
noise generated from felling of items in house can be
minimized.
Maintenance of automobiles:
• Regular servicing and tuning of vehicles will reduce
the noise levels. Fixing of silencers to automobiles, two
wheelers etc., will reduce the noise levels.
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5.5. Control of Noise Pollution
contd…
Control over vibrations:
The vibrations of materials may be controlled using
proper foundations, rubber padding etc. to reduce the
noise levels caused by vibrations.
Low voice speaking:
Speaking at low voices enough for communication
reduces the excess noise levels.
Prohibition on usage of loud speakers:
By not permitting the usage of loudspeakers in the
habitant zones except for important meetings / functions.
Now-a-days, the urban Administration of the metro
cities in India, is becoming stringent on usage of
loudspeakers.
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5.5. Control of Noise Pollution
contd…
Selection of machinery:
• Optimum selection of machinery tools or equipment reduces excess
noise levels.
• For example selection of chairs, or selection of certain
machinery/equipment which generate less noise (Sound) due to its
superior technology etc. is also an important factor in noise
minimization strategy.
Maintenance of machines:
• Proper lubrication and maintenance of machines, vehicles etc. will
reduce noise levels.
• For example, it is a common experience that, many parts of a
vehicle will become loose while on a rugged path of journey.
• If these loose parts are not properly fitted, they will generate noise
and cause annoyance to the driver/passenger.
• Similarly is the case of machines. Proper handling and regular
maintenance is essential not only for noise control but also to
improve the life of machine.
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5.6. Prevention of noise pollution
What is Pollution Prevention?
• "the use of processes, practices, materials,
products, substances or energy that avoid or
minimize the creation of pollutants and waste,
and reduce the overall risk to the environment
and human health"
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5.6. Prevention of noise pollution
•
Construction of soundproof
rooms for noisy machines in
industrial and manufacturing
installations must be encouraged.
•
This is also important for
residential
building—noisy
machines should be installed far
from sleeping and living rooms,
like in a basement or garage.
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5.6. Prevention of noise pollution
contd…
• Use of horns with jarring sounds, motorbikes
with damaged exhaust pipes, noisy trucks to be
banned.
• Noise producing industries, airports, bus and
transport terminals and railway stations to
sighted far from where living places.
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5.6. Prevention of noise pollution
contd…
• Community law enforcers should
check
the
misuse
of
loudspeakers,
worshipers,
outdoor parties and discos, as
well as public announcements
systems.
• Community laws must silence
zones near schools / colleges,
hospitals etc.
• Vegetation (trees) along roads
and in residential areas is a good
way to reduce noise pollution as
they
absorb
sound.
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5.6. Prevention of noise pollution
contd…
• Noise Pollution can come from cars,
construction work, people yelling and
anything that creates loud noise in the air.
Some of the slogans
– Keep the noise down or the noise will keep you
down.
– Noise can fill your ears, and put you in tears.
– Don’t be a clown, keep the noise down.
– Sometimes you say more by not saying anything at
all.
– There is No Peace without Quiet.
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2 marks
1. What is noise?
• In simple terms, noise is unwanted sound. Sound
is a form of energy which is emitted by a vibrating
body and on reaching the ear causes the
sensation of hearing through nerves.
2. How can noise affect us?
• Temporary Deafness: This Persists for about 24
hours after exposure to loud noise.
• Permanent Deafness: Repeated or continuous
exposure to noise of around 100 dB results in
permanent hearing loss.
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2 marks
3. How can we control the Noise source?
• Reducing the noise levels from
1.
2.
3.
4.
5.
6.
contd…
domestic sectors,
Maintenance of automobiles,
Control over vibrations,
Low voice speaking,
Prohibition on usage of loud speakers and
Selection of machinery
4. What is the difference between sound and noise?
• Noise is unwanted sound. Sound is a form of energy
emitted by a vibrating body and on reaching the ear it
causes the sensation of hearing through nerves.
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2 marks
contd…
5. List out typical sources of noise pollution.
Source Noise level
dB(A)
1. Air compressors
95-104
2. Quiet garden
30
3. 110 KVA diesel generator
95
4. Ticking clock
30
5. Lathe Machine
87
6. Computer rooms
55-60
7. Milling machine
112
8. Type institute
60
9. Oxy-acetylene cutting
96
10. Printing press
80
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2 marks
contd…
6. What is the purpose of frequency analysis?
• The frequency analysis allow to separate the
main components of the signals by dividing
the frequency range of interest into smaller
frequency bands using a set of filters.
7. What are the impacts of noise?
• Physiological effects, Loss of hearing, human
performance, Nervous system: Annoyance,
Sleeplessness, Damage to material.
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2 marks
contd…
8. What are the methods to control noise pollution?
• Identify the noise sources from each zone
• Find out the noise levels of each zone
• Compute Ldn values
• Identify the likely causes of noise from noise sources.
• Develop methodologies to solve the problem
• Attempt to solve
9.What are the noise exposure limits in a workspace
environment?
• Regulations prescribe that, noise level of 90 dB (A) for more
than 8 hr continuous exposure is prohibited. Persons who
are working under such conditions will be exposed to
occupational health hazards.
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2 marks
contd…
10.What are the ambient noise limits?
• Sounds produced by all vibrating bodies are not audible. The
frequency limits of audibility are from 20 HZ to 20,000 HZ.
• Noise generation is associated with most of our daily activities. A
healthy human ear responds to a very wide range of SPL from - the
threshold of hearing at zero dB, uncomfortable at 100-120dB and
painful at 130-140 Db. Due to the various adverse impacts of noise
on humans and environment noise should be controlled.
11.Write short notes on Decibel, dB and Ldn
• DECIBEL is measurement unit of sound, represented by dB.
• The day night equivalent noise levels of a community can be
expressed as -Ldn ,
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2 marks
contd…
12.Write short notes on Infrasonic and Ultrasonic
• Infrasonic: The sound of frequency less than 20HZ.
• Ultrasonic: The sound of frequency more than 20,000 Hz
13.Equipment used in the measurement of noise levels
• Sound level meter
• Type-0 : Laboratory reference standard
• Type-1: Lab use and field use in specified controlled
environment
• Type-2: General field use (Commonly used)
• Type-3: Noise survey Impulse meters For measurement of
impulse noise levels e.g. hammer blows, punch press
strokes etc
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2 marks
contd…
14.What is noise?
• Noise is defined as unwanted sound. A sound might be
unwanted because it is loud, distracting, or annoying.
15.How is noise measured?
• Literally speaking, noise can't be measured directly,
since there is no instrument for objectively detecting
how "unwanted" something is.
• What can be measured is the sound level, a
quantification of a sound's pressure or intensity and
related to its loudness. Sound level is measured in
decibels (dB), by a device called a sound level meter.
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2 marks
contd…
• 16. What is a decibel?
• What are typical decibel levels of some common sounds? A whisper
is 30 dB, conversational speech is 60 dB, and someone shouting at
you from an arm's length away is 85 dB.
• Noise levelsof home appliances range from 50 dB (a refrigerator) to
95 dB (a food processor).
• Lawn equipment and power tools have noise levels of 80–120 dB.
• 17.How many decibels can the human ear handle?
• Immediate and irreversible nerve damage can be caused by sounds
at 140 dB or higher (120 dB in young children).
• However, damage also occurs at lower sound levels, and this harm
accumulates over time.
• Any sound above 85 dB can cause wear and tear on your ears that
reduces your hearing acuity over time.
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2 marks
contd…
18. What is the loudest sound possible?
• Sound is normally carried in air as a pressure wave. When the
pressure of a sound wave becomes as high as the air pressure itself,
the sound becomes a shock wave.
• Normal air pressure at sea level is 14.7 pounds per square inch (psi),
or 101,325 Pascals (Pa), which is equivalent to 194 decibels (dB).
• So 194 dB is the loudest sound possible in air at sea level; beyond
that point it becomes a shock wave. (Sound waves that are
transmitted through water or other substances would have
different limits.)
19. What are the effects of noise on human health?
• Noise has direct physiological effects such as hearing damage
(including hearing loss and tinnitus, or ringing in the ears), as well
as cardiovascular and hormonal disturbances.
• Indirect effects include sleep loss, interference with concentration
and learning, mood changes and aggression, and social isolation.
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2 marks
contd…
20. How does noise affect babies and children?
• Because the ear canal of a young child is smaller than an
adult's, sound pressure is up to 20 dB greater than that in
an adult ear.
• In addition to the threat to a child's hearing, noise causes
physiological and mental stress, and significantly impacts
learning and cognitive development.
• Background noise also interferes with speech perception
and language acquisition.
20. What is "white noise"?
• White noise is a sound similar to radio static, or the sound a
fan makes, that is often used to mask unpleasant sounds.
• Some people find it helpful for sleeping, and it can be a
soothing sound for babies.
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2 marks
contd…
21.What are the most common sources of noise pollution?
• Worldwide, the most common sources of noise pollution are cars, trucks,
and other motor vehicles.
• Planes and trains also contribute to noise pollution. Other sources include
factory machinery, power tools, and construction equipment.
22.What problems does noise pollution cause for people?
• The World Health Organization (WHO) cites seven categories for the ways
noise adversely
• affects human health:
• Noise-induced hearing impairment
• Interference with speech communication
• Sleep disturbances
• Cardiovascular and physiological effects
• Mental health effects
• Effects on performance of tasks
• Annoyance and effects on behavior
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contd…
24. What are the laws regarding noise pollution?
• Occupational noise is treated as a health and safety issue and is
regulated at the state or national level in many countries.
• Community noise is typically regarded as a nuisance issue rather
than a matter of health, and is normally regulated at local levels of
government.
• The regulations and levels of enforcement vary widely across
different communities, and worldwide.
• Noise-generating products such as automobiles and aircraft may be
controlled by industry regulations, and building codes may set
requirements for reducing sound transmission in new building
construction projects.
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