UNIT KEJURUTERAAN ALAM SEKITAR UNIT KEJURUTERAAN ALAM SEKITAR JABATAN KEJURUTERAAN AWAM JABATAN KEJURUTERAAN AWAM

POLITEKNIK SULTAN IDRIS SHAH

CHAPTER 8CHAPTER 8

NOISE MITIGATION NOISE MITIGATION AND MEASUREMENTAND MEASUREMENT

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Upon completion of this course, student should be able to :

Explain the noise pollution mitigation for reduce noise pollution, control noise pollution on sources and protect noise pollution from receiver.

Apply noise mitigation to overcome noise pollution Explain noise pollution measurement Apply noise pollution equipment (Sound Level Meter and Dosimeter) List the procedure of calibration for noise pollution equipment Describe measurement procedures Determine physical conditions for measurement Determine the regulations on noise pollution control (motor

vehicles) 

Noise pollution mitigation for reduce noise pollution, control noise pollution on sources and protect noise pollution from receiver

Reduce noise pollution

Noise pollution can negatively impact the body in significant ways, including elevated blood pressure, impaired cognitive functioning, and other effects of chronic stress.

Limit The Noise -Double-Paned Windows and Weather Stripping

Basic control of the noise path Noise can be reduced if the passage was blocked

by obstacles and spread like a wall, land reclamation and so on. This is because the sound has been absorbed or filtered and dispersed by the blockage.

For example, the construction of the wall can reduce noise by 10-15 dBA. Principles of access and dissemination controls on noise and suitable for use in the City to reduce noise. However, the factors of height, thickness and type of wall used to determine the level of noise can be reduced.

Basic control of the listener Control principles to the listener means to prevent

noise from the sound received by the audience. Through this principle, an action may be taken on behalf of the noise.

What can be done is to put the receiver noise is far from the noise source or place obstacles that can prevent a lot of noise until the receiver noise.

Methods of site planning and good landscape design is one method that is best done based on this principle. These methods include the layout plan, landscape approach and area activities. In addition, the use of hearing protection devices are also effective to reduce the noise problem.

Barriers through the provision of physical resistance

Barriers through the provision of physical resistance Physical resistance - usually done by setting up a brick or concrete

wall and land reclamation. Appropriate to prevent the traffic noise. Planting of trees and open spaces - trees with large leaves and thick

and heavy branches can be used as noise insulation. Non-residential buffer zone - this method means putting activity is

less sensitive to noise as a buffer zone between areas sensitive to noise. Example, shops, offices or light industry which is placed between a noisy road and residential areas.

Traffic management Separate the motor from the receiver by means such as the

construction of ring roads, provision of pedestrian walkways, limiting the vehicle through an area with a limitation of time and prepare and set the minimum distance between new residential traffic.

Improve the flow of traffic to reduce congestion for example through the provision of direct access and encourage use of public transport.

Use of barrier and buffer zones. Isolate the vehicle from the recipient - separate the heavy vehicles

to home by providing the street itself.

Other methods of control

The provision of pedestrian. Encourage the use of public transport. Layout of the house.

Noise mitigation is a set of strategies to reduce noise pollution.

The main areas of noise mitigation or abatement are: transportation noise control, architectural design, and occupational noise control.

Roadway noise and aircraft noise are the most pervasive sources of environmental noise worldwide, and little change has been effected in source control in these areas since the start of the problem a possible exception being the development of hybrid and electric vehicles.

Roadway The most fertile areas for roadway noise mitigation

are in urban planning decisions, roadway design, noise barrier design, speed control, surface pavement selection and truck restrictions.

Speed control is effective since the lowest sound emissions arise from vehicles moving smoothly at 30 to 60 kilometres per hour.

Above that range, sound emissions double with each five miles per hour of speed.

At the lowest speeds, braking and (engine) acceleration noise dominates. Selection of surface pavement can make a difference of a factor of two in sound levels, for the speed regime above 30 kilometres per hour.

Quieter pavements are porous with a negative surface texture and use medium to small aggregates; the loudest pavements have a transversely grooved surface, and/or a positive surface texture and use larger aggregates.

Surface friction and roadway safety are important considerations as well for pavement decisions.

A computer model is required to design the barrier since terrain, micrometeorology and other locale specific factors make the endeavor a very complex undertaking.

For example, a roadway in cut or strong prevailing winds can produce a setting where atmospheric sound propagation is unfavorable to any noise barrier.

Aircraft

Variations in aircraft types, flight patterns and local meteorology can be analyzed along with benefits of alternative building retrofit strategies such as roof upgrading, window glazing improvement, fireplace baffling, caulking construction seams and other measures.

The computer model allows cost effectiveness evaluations of a host of alternative strategies.

Architectural Solution

Firstly, airborne sound travels through walls or floor and ceiling assemblies and can emanate from either human activities in adjacent living spaces or from mechanical noise within the building systems.

The second type of interior sound is called Impact Insulation Class (IIC) transmission.

Designing special purpose rooms has more exotic challenges, since these rooms may have requirements for unusual features such as concert performance, sound studio recording, lecture halls.

Industrial

The most common techniques for noise protection of workers consist of shock mounting source equipment, creation of acrylic glass or other solid barriers, and provision of ear protection equipment.

In certain cases the machinery itself can be re-designed to operate in a manner less prone to produce grating, grinding, frictional or other motions that induce sound emissions.

Other solutions may involve researching the quietest models of office equipment, particularly printers and photocopy machines.

EXPLAIN NOISE POLLUTION MEASUREMENT

In 1929 when the New York City noise survey was in progress, Dr. Harvey Fletcher from the Bell Telephone Laboratories explained in a radio talk “How Noise is Measured and Why.” It continues to be helpful to illustrate how a noise level of 90 decibels really sounds. (He used a recording of applause at one of the receptions for Charles Lindbergh.) He demonstrated a reduction of noise level of 10 decibels. (He did not say 10 dB.) He gave the elements of “a piece of apparatus” that today we call a sound‐level meter. He led to the easy conclusion that noise level is the same as sound level, and that you measure it with a sound‐level meter. There was no entanglement with logarithms; simply “the decibel is a unit used to describe an amount of noise.”

MEASUREMENT OF NOISE :

The two most important measurement of noise are, sound pressure and sound intensity, these are measured in different units, and the scale of the magnitude id different and very

large in relation to noise. The unit of measurement of sound is

decibel (dB). It is ratio expressed as logarithmic scale

relative to a reference sound pressure level intensity measured (I )

Sound Intensity Level = 10 log 10 ___________________ reference intensity (Io)   The reference intensity used is the “threshold of hearing” which is a

sound that can be first heard at sound pressure of 2X105 N / M2 of a sound intensity of 10 – 12 W / M2 .

It is quite important to note that doubling of sound pressure produces an increase of 6 dB

and doubling of sound intensity produces an increase of 3 decibels, which is implicit in

the logarithmic scale for sound measurement.

Apply Noise Pollution Equipment

Sound Level Meter Sound level meters measure sound pressure level and

are commonly used in noise pollution studies for the quantification of almost any noise, but especially for industrial, environmental and aircraft noise.

Sound level meters, also known as decibel meters and noise dosimeters, are designed to measure the sound pressure of a particular event.

The sound level meter is the most common device used to measure overall workplace noise by OSHA

The sound level meter is generally placed in a central location at a worksite to collect data, which is then analyzed to determine average, lowest and highest noise levels during a given work period.

Data from sound level meters can be used to determine proper hearing protection for employees, design sound-proof or sound-absorbing materials and position them correctly to absorb sound, and to measure the effect of sound on the general population, which can also lead to reduction or absorption measures.

How To Use Sound Level Meter Insert the battery into the sound-pressure level meter. Point

the microphone of the SPLM at the source and take the measurements of the sound coming out of the speakers.

A wind shield must be used if the air velocity is noticeable. It should anyway be used all the time as a dust shield.

Choose the response time, either fast or slow. Use slow to measure average sound levels and fast to measure peak levels.

Mount the SPLM on a tripod by screwing it into the mount threads on the bottom of the SPLM. Using a tripod will get you the most accurate measurements.

Calibrate your speakers by playing noise from your CDs through your speakers.

Be sure to stand off to the side of the SPLM while doing this to ensure accuracy. Should be to get a reading as close to 0 for each of the test tones. Fiddle with the speaker placement to get this.

The SLM must be calibrated before any measuring session using a calibrator . If the temperature of the instrument is significantly different from the ambient temperature where it will be used, it should be first warmed up before calibration and use. The calibration must be checked at the end of the session. If the instrument is not calibrated anymore, the data might have to be discarded and the reasons for this calibration change should be investigated as this might indicate an important malfunctioning of the instrument.

Sound Level Meter Calibrator

Calibrate the sound level meter before conducting the stationary sound test. Use only calibrators approved by the sound level meter manufacturer : o Turn on the calibrator and the sound level

meter. o Set range switch to correct range. o Make sure calibrator is mounted to sound level

meter correctly. o Adjust sound level meter to give correct

reading.

Dosimeter Dosimeters measure an individual's or an object's exposure

to something in the environment - particularly to a hazard inflicting cumulative impact over long periods of time, or over a lifetime.

The noise dosimeter is similar to sound level meters, but instead of being positioned in one place, it is worn by individual employees.

Employees wear the dosimeter throughout their shifts, and the dosimeter collects information about how, when and how much noise they are exposed to during a typical work day.

A dosimeter can calculate on the spot whether an employee is nearing or over the OSHA limits for noise doses in a day or over longer periods of time.

Dosimeter data is used to determine hearing protection for workers, schedule work in noisy areas in ways that are safer for employees, and design sound absorption materials and determine their placement

Use of Noise Dosimeter

The noise dosimeter is clipped to the workers' clothes with the microphone close to the ear, and can be worn without hampering work. The dose provided by the instrument is of course dependent on the duration during which the instrument is used.

Therefore, it should first be corrected for an 8 hour period and then converted to the daily noise exposure (LEX,8) level according to the relevant formula (ISO or OSHA).

It is important to know that some old dosimeters do not take into account levels below 89 dB(A) or 80 dB(A), as they assume that lower levels do not lead to hearing impairment.

The LEX,8 is then physically not correct. These dosimeters are obsolete and should be discarded. On certain instruments, a warning marker is activated if the peak level ever exceeds 140 dB.

It is worth noting that the characteristics of the dosimeters have never been standardized.

Furthermore, they are extremely limited as they provide one single value at the end. It is strongly recommended to abandon this type of instrument and use the personal sound level meters described in the next section.

The Procedure of calibration for noise pollution equipment

Procedures sound level meter: - Height (m) of the SLM device is 1.2 meters

above ground level. Angle / degree position SLM device is 450.

Distance from the root SLM noise is not more or less than 2.5 meters.

Spout in SLM is directed to cause noise. 

Position intake data for the study of noise levels in the environment.

The steps for the measurement of environmental noise levels. Position distance for data taking in the surrounding noise level. Position distance for data taking the noise level in the building. The method of measurement is made more observations in the

data taken for 12 hours from 6 am to 6 pm. This is to see the difference and comparison of noise that occurs on that day. The data taken was done in 15 minutes in the next 12 hours.

Procedure Dosimeter :-

Dosimeter measurement procedures include: Advising the employee being monitored. A pre and post calibration and battery check. Microphone located on the individual’s shoulder and

fastened to not interfere with safety or performance of the individual.

The dosimeter shall be reset and started according to manufacturer’s instructions.

Dosimeter is set to standby at end of measurement period.

Measurement procedure

1. The microphone of the sound level meter should be located between a height of 1.2 and 1.5 metres above the ground.

2. The measurement point should be no less than 3.5 metres from any reflective surface, such as walls or buildings, other than the ground.

3. The surface on which a noise source (such as an air conditioner) is located and the property boundary from where the noise is emitted are not considered as reflective surfaces.

4. Where it is not possible to locate the measurement point 3.5 metres from reflective structures, such as outdoor measurements near buildings, the preferred measurement positions are one metre from the façade and 1.2 to 1.5 metres above each floor level of interest.

Equivalent continuous sound pressure level (Leq) for noise

under assessment The sound level meter must be set on A-frequency weighting and equivalent continuous sound pressure level (Leq) integrating function. The level should be determined over a sufficiently long time to be representative of the noise and will be measured for not less than five minutes. The level must not include extraneous noise that could affect the level of the noise being assessed — extraneous noise must be excluded using the pause function of the meter.

Measurement settings

PHYSICAL CONDITION FOR NOISE MEASUREMENTPLACE OF MEASUREMENTWhen the premises receiving the noise has a building or

buildings and surrounding land, the noise may be measured either outside the buildings and within the boundary, or inside the buildings, but can only be measured inside if

the use of the building is directly associated with the type of premises receiving the noise, for example, the building is an office on a Commercial premises or a house on a noise-sensitive premises; and

the building is of a type of construction that is typical of buildings so used. For example, one would not carry out a sound measurement inside a tent, as its construction is not typical of a house. Where the premises receiving the noise is a caravan park or camping ground, measurements are to be made outside of a caravan, camp or park home.

The measurement is taken inside where - there is no surrounding land; or the noise is coming through a common

wall or from another part of the building. Where a measurement is made inside, the measured level is adjusted by –

+15 dB if the external doors and windows are shut; or

+10 dB if the external doors and windows are open.

Sketch measurement position on the standard noise measurement form and include:

living areas identified as likely to be particularly affected by the source noise;

noise sensitive areas of premises; noise source direction and approximate

distances; relevant barriers, mounds, vegetation and

ground cover in the separation zone; wind direction and speed; location of measurement position(s) indicating

distances from fixed reference points which are unlikely to change; and

identification of other land uses in the vicinity of the affected premises.

MICROPHONE POSITION

The microphone must be at least 1.2 metres above the ground and at least three metres from any other sound reflecting surface, if practicable, to avoid the effect of sound reflections. Indoor measurements must be made at least one metre from any open external window or door.

Measurement of airblast levels during blasting must be done outdoors, with the microphone 1.2 to 1.6 metres above the ground and at least five metres from any other reflecting surface.

8. Determine The Regulations On Noise Pollution Control (Motor Vehicles)

Environmental Quality Act, 1974 is an act associated with noise control even though it has no specific regulations on this issue.

The minister of science, technology and environment after consultation with the environmental quality council, may make laws with respect to the noise problem and determine the noise level to be acceptable.

The Act also states that other than those already granted a license, no person shall remove or cause or permit the occurrence of any sound louder in volume, intensity or quantity of the conditions specified.

Regulations under the Environmental Quality (Motor Vehicle Noise, 1987), Minister of Science, Technology and Environment with the Department of Road Transport plays an important role to control the maximum level of noise by introducing a line of law.

Environmental Quality (Motor Vehicle Noise) Regulations 1987, and shall come into force on the 16th July 1987.

These regulations are the maximum permissible noise levels for some categories of vehicles and the maximum permissible noise level in the unit dB (A) in accordance with the standards set.

There are three standard set of standard A which is allocated to the maximum permissible sound levels for motor vehicles with two or three wheels.

While Standard B was for the maximum permissible sound levels for vehicles with two or three wheels manufactured or assembled on or after the January 1, 1990.

Further, the Standard C is allocated to the maximum permissible sound levels for motor vehicles having more than three wheels.

SCHEDULE 1: MAXIMUM SOUND LEVEL PERMITTED FOR MOTOR VEHICLES HAVING TWO WHEELS OR THREE WHEELS

STANDARD ACategory of vehicle Maximum sound level

Permitted (dB (A))1. 125 cc. and below 95

2. Above 125 c.c 99

STANDARD B

SCHEDULE 2: MAXIMUM SOUND LEVEL PERMITTED FOR MOTOR VEHICLES HAVING MORE THAN THREE WHEELS

Category of vehicle Maximum sound level Permitted (dB (A))

1. Below 90 cc. 92

2. 90 c.c and above 95

Category of Vehicle Maximum sound level permitted (dB (A))

1. Used for the carriage of passengers and comprising not more than 9 seats (including the driver’s seat)

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2. Used for the carriage of passengers and comprising more than 9 seats. Permitted maximum weight does not excedd 3.5 tonnes

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3. Used for the carriage of goods. Permitted maximum weight does not exceed 3.5 tonnes. Engine is less than 200 h.p. DIN

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4. Used for the carriage of passengers and comprising more than 9 seats. Permitted maximum weight exceeds 3.5 tonnes. Engine is less than 200 h.p.DIN

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5. Used for the carriage of passengers and comprising more than 9 seats. Permitted maximum weight exceeds 3.5 tonnes. Engine is 200 h.p DIN or more

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6. Used for the carriage of goods. Permitted maximum weight exceeds 3.5 tonnes.7. Used for the carriage of goods. Permitted maximum weight exceeds 3.5 tonnes. Engine is 200 h.p. DIN or more

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