4. DEFINITIONS
• Unwanted sound ----> too subjective
- one man's sound may be another man's
noise
• Better definition : Wrong sound in the
wrong place at the wrong time
5. SOURCES OF NOISE
• Many & varied
Ex:
Automobiles, factories,
industries, aircrafts.
Railway junctions, traffic
round-abouts, bus
terminuse , airports.
Use of pressure horns,
recreational noises of
loudspeakers with full
volume during festivities.
Domestic noises: radios,
transistors,T.V sets.
7. LOUDNESS
• Depends upon the amplititude of vibrations
which initiated the noise.
• Unit : decibels (dB)
• Reference sound pressure = smallest
distinguishable noise
- 0.0002 microbar or dynes/cm2
- 1 dynes = 1/106 th of atmospheric
pressure
8.
9. FREQUENCY
• Number of cycles per
unit time.
• Unit : Hertz (Hz) , 1
Hz is equal to one
wave per second
• Range audible to
human:20-20000 Hz
• < 20 Hz - infraudible
• >20000 Hz -ultrasonic
10. EFFECTS OF NOISE EXPOSURE
• AUDITORY EFFECTS
i. Auditory Fatigue
- appears in the 90 dB region & greatest in
4000 Hz.
- Side effects : whistling & buzzing in the
ears
11. ii. Deafness/Hearing loss
- maybe temporary / premanent
Temporary Hearing Loss:
- results from a specific exposure to noise
- the disability disappears after a period of
time upto 24 hours following the exposure
- occurs in frequency : 4000-6000 Hz
12. Permanent Hearing Loss
- repeated or continous exposure to noise
around 100 dB.
- In this, inner ear damage occurs
- Exposure to noise > 160 dB may rupture
the tympanic membrane & cause
permanent loss of hearing
13. • NON-AUDITORY EFFECTS
i. Annoyance
- Primarily a psychological effect
- Neurotic people are more sensitive to
noise than balanced people
- Workmen exposed to higher intensity of
noise in occupational capacities are often
irritated, short tempered & impatient.
14. ii. Efficiency
- Low level of noise--->better mental
concentration---> increase work output
iii. Physiological changes
- Rise in BP, rise in HR, rise in itracranial
pressure, increase in sweating
- Interferences with sleep
- Causes visual disturbances
15. iv. Interference with speech
- Frequencies causing most
disturbances to speech
commuication : 300-500 Hz.
- This is commonly produced
by road & air traffic.
- For good speech intelligibility,
it is considered that speech
sound level must exceed the
SIL (Speech Interference
Ievel) by 12 dB.
16. v. Economic loss
- The potential cause of
noise induced hearing
loss to industry is
quite great.
17. CONTROL OF NOISE
• CAREFUL PLANNING
OF CITIES
- Division of the city into
zones with separation of
ares concerned with
industry & transport.
- The separation of
residential areas from the
main streets by means of
wide green belts.
- Widening of main streets
to reduce the noise
penetration into the
dwellings.
18. • CONTROL OF
VEHICLES
- Heavy vehicles
should not be routed
into narrow streets.
- Vehicular traffic in
residential areas
should be reduced.
- Indiscrimate blowing
of the horn & use of
pressure horn should
be prohibited.
19. • TO IMPROVE
ACOUSTIC
INSULATION OF
BUILDING
- The best arrangement is
the construction of
detached buildings rather
than a single large
building or one that is
continous
- Buildings should be
sound-proof where
necessary
20. • PROTECTION OF
EXPOSED PERSON
- For workers consistently
exposed to noise > 85 dB
in the frequence bands >
150 Hz.
- Workers must be
regularly rotated to from
noisy ares to
comparatively quiet posts
in factories.
- Periodical radiogram
check-ups.
- Use of ear plugs, ear
muffs.
21. • LEGISLATION
- Workers have right to
claim compensation if
they have suffered a loss
of ability to understand
speech.
• EDUCATION
- Education through all
available media is
needed to highlight the
importance of noise as a
community hazard.
22. SUMMARY
• Man is living in a increasingly noisy
environment. The 20th century has been
described as the "Century of Noise".Noise
has become a very important stress factor
in the environment of man. Hence,
participation of people in noise abatement
programmes is necessary to combat this
problem.
