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ENVT 9NOISE

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NOISE

Definedas wrong sound, in the wrongplace at the wrong time

Source :- automobiles, factories, industries,aircraft etc.

Noise levels are more near railway

stations, traffic roundabouts, bus terminus& airports.

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Properties :-

1)loudness:- depends upon amplitude of

the vibrations which initiated the noise.

It is measured in decibels(dB).

daily exposure of85dB is tolerated bynormal individuals.

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2)frequency :- is denoted in hertz(Hz).

1 Hz = one wave/ sec

human ear can hear freq from 20 to 20,000 Hz,

but this range is reduced with age & othersubjective factors.

Range of vibrations above 20,000Hzareultrasonic.

Instruments used in measurement SOUNDLEVEL METER, AUDIOMETER

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Sound levels of some Noises.

Noise

a) whisper

b) speech, 2-3 people

c) music on radio

d) children shouting

e) vacuum cleaner

f) piano

g) jet take off

Sound level(dB)

10

73

85

79

76

86

150

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EFFECTS OF NOISE

1)AUDITORY:-a) auditory fatigue at 90db, upto 4000hz

b) deafness temp or permanent,4000 6000 hz

Repeated exposure to sound more than 100db leads to

permanent deafness due to damage to inner ear. 2) NON AUDITORY:-

a) interference with speech.

b) annoyance

c) decreases mental efficiency. d) physiological changes : rise in BP, rise in intracranial

pressure, increase In HR, increase in sweating.

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CONTROL

1) CAREFULL PLANNING OF CITIES

2) CONTROL OF VEHICLES

3) IMPROVE ACOUSTICS OFBUILDINGS.

4) PROTECTION OF EXPOSED

PERSONS.

5) EDUCATION.

6) LEGISLATION.

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THANKYOU