Lec#06 EnvE - Noise Pollution

8/10/2019 Lec#06 EnvE - Noise Pollution

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Noise PollutionLecture # 6


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NOISE CONTROLEnvironment technologies

INTRODUCTION

Noise is unwanted sound. The word has been derivedfrom Latin word nausea meaning noise. The sound is a

wave of energy, consists of special kind of waves, whichare usually transmitted through air in the form of pressurewaves. These waves are received by hearing apparatusof animals including man transformed into electricalimpulses in the ear and carried to brain which enable usto hear. The intensity of sound is measured in decibels

(d=10 and Bell is the name of scientist Alfred GrahamBell). Technically, a decibel (dB) is the amount of soundpressure.


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The intensity of loudness is measured on a scale called decibelscale. Or B-scale. The scale starts from 0- dB which is considered as thethreshold of hearing the faintest sound which human can hear.

A sound of 10dB is ten times louder than 0dB. A sound of 20dB is 10 x 10 or 100 hundred times louder, of 30dB 10 x 10

x10 or 1000 times, 40dB is 10 x 10 x 10 x 10 or 10,000 times while asound of 50dB is 10 x 10 x10 x 10 x 10 or 100,000 times louder thethreshold of human hearing.

Examples: Alarm clock---70 80dB.Public library 30 40 dBJet planes taking off 140- 150 dB

Ambient air quality standards noise level should lie between 50 75dB inday time and 40 70 at night time.

MEASUREMENT OF NOISE


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o Industrial noiseo Traffic noiseo Domestic noise

It may be natural, such as wind, thunder, movement of water or man made. Thesymbols man made civilization are Jet plane, vehicles, railway engines,factories generators, construction machinery, television, radio, public addresssystems have something common - it is the noise .The most offending noise source are compressors, generator furnaces, grindingmills, releasing valves etc. that are used in many industrial processes and areinstalled in partially or closed or open sheds. 80 120 dB noise level iscommon to most units which is hazardous.

SOURCE OF NOISE POLLUTION


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Noise pollution is traditionally not placed among the topenvironmental problems facing the society; however, it is one of themore frequently encountered sources

Sources of noise pollution are extremely diverse and are constantlyincreasing as more and more noise-generating products becomeavailable to consumers.

An estimated 6% citizens are exposed to noise that poses a threatto their hearing.

In today's mechanized world it is virtually impossible for an activeperson to avoid exposure to potentially harmful sound levels.



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Wild life too have been affected by noise. Health status ofseveral zoo animals deers, lions, rhinos, are known to beaffected by noise. They appear dull and inactive. Several

migratory birds have stopped resting in a habitat close to noisycities. Grizzly bears and kangaroo rats in Malaysia have beenaffected by noise. They leave that habitat and move to calmplaces. This change of habitats alters their food habits andhealth.

EFFECT OF NOISE POLLUTION ON WILD LIFE


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NOISE CONTROL

General control measures include alteration ofmachines and equipment to gather up-dated machinery

regarding noise prevention.

Noise can be tackled through:

Reductionat source Change to quietermethods Prevention orreduction of propagation



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NOISE CONTROL

It is often possible to reduce noise radiation from productionequipment, material handling, and work in progress; forexample by damping sound radiating panels, quieteningpower sources and transmissions, and reducing noise fromcompressed air exhausts.

Sometimes machine alterations do not give sufficiently goodresults.

In such cases effort might be better aimed at changing theworking methods and processes themselves.

Reductionat source



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NOISE CONTROL

Changing the method of work is the only way to get to gripswith noise generation; it requires that production equipmentor part of it must be replaced and one must be aware of theavailability of less noisy equipment for both production andmaterial handling.

Change to quietermethods



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NOISE GUIDELINES

For all noise control efforts a target noise level must be set. A highest level must

be defined for eachplace of equipment or room

Type of room Highes sound levelguideline (dB)

Conference room 35

Office 40

Workshop office, restroom

45

Laboratory,measurement room

50

Canteen 50

Repair shop 60

Production areas 75

Fan room, compressor

room

90



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NOISE CONTROL TIPS

Machinery have to be updated to control noise pollution. Handling material can be done by choosing conveyor belts

and controlling the speed of conveyor belt transports. Attenuation by using absorbent materials is one of the key

techniques to ensure that rooms and workshops do notcommunicate noise pollution to each other. To ensure so,best practices are providing sound isolated rooms.



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RESULTS for NOISE CONTROL

Mounting an absorbent roof or ceiling in a room will ingeneral give a noise reduction of between 3 and 5 dB.

Exceptionally, up to 10 dB can be obtained. Damping of vibration of small production machines by

applying damping material can give between 3 and 10 dBattenuation.

Factory-made screens can reduce noise from between 5and 15 dB.

Noise control of new projects can be difficult to manage andimplement, but very cost-effective at the long term.


Lec#06 EnvE - Noise Pollution

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