NOISE INDUCED HEARING LOSS ! ~ Shri.Dr.Ch.Ramanachary Ji, MS ENT, Professor and HOD Prathima Institute of Medical Sciences, Karimnagar, Telangana State, India

2. INDIAN YOUTH SECURED ORGANISATION / ANTI-CORRUPTION TEAM INDIA / SAFER INDIAN ROADS
YOUNG INDIA MISSION / KARIMNAGAR CYCLE CLUB

3. NOISE INDUCED HEARING LOSS
INDIAN YOUTH SECURED ORGANISATION / ANTI-CORRUPTION TEAM INDIA / SAFER INDIAN ROADS
YOUNG INDIA MISSION / KARIMNAGAR CYCLE CLUB

4. SOUND
Sound is alternate contraction and rarefaction of
molecules travelling in a wave form

5. UNIT OF SOUND
 Decibel (dB)- Unit of Measuring sound
 Logarithmic value of ratio of standard sound to
the sound in question.
 Zero decibel is the minimum intensity a healthy
person can hear
 100 db is 10 (1000 crores) intensity ampified

6. SOUND LEVELS
 Normal Speech 30-40 db
 Shouting 50 db
 Ordinary car horn 70 db
 Air Horn 90-100 db
 Rock Music 100 db
 Busy street noise 80-100 db

7. NOISE
 Any abnormal sound that irritates human beings is called
noise.
 Unwanted
 intolerable
 Undesirable byproduct of technological advance.
 Nuisance and health hazard too.

8. INDIA
World capital of noise
metropolitan cities > 90 decibels
(Decibel is the unit of sound pressure expressed in logarithmic scale.)

9. SOURCES OF NOISE
POLLUTION
 Traffic- (Automobiles, Trains, Aeroplanes).
 Loudspeakers.
 Religious and social ceremonies.
(Studies by SOCLEEN in Bombay during Ganapathi festival in 1980
showed that noise levels was 97 decibels)
 Industrial: Factories, construction activities,
machineries.
 High decibel music.
 Home noise - TVs , Radios, music players, high
speed fans, air conditioners, home appliances.
 Gunfire exposure , Explosions

10. EFFECTS OF NOISE
POLLUTION
 Humans
1. Systemic Effects
2. Effect on Hearing
3. Emotional
4. Mental
5. Social
 Animals
 Inanimate Things

11. SYSTEMIC EFFECTS
 Increase in heart rate
 Blood sugar increase
 Changes in respiratory rate
 Hypertension.
 Peptic ulcer, Hyper acidity
 Asthmatic attacks
 Heart attacks
 Changes in pregnancy
 Giddiness in Meniere’s

12. Noise Trauma
◦ It is generally agreed that, for the human ear, sound levels below 80 dB
are unlikely to cause hearing damage, no matter how long one is
exposed to them.
◦ Sounds of 130 dB or greater will cause hearing damage after even
short time periods in almost all exposed individuals.
◦ Hearing loss caused by excessive noise can be divided in to two groups
1. Acoustic Trauma
2. Noise Induced Hearing Loss (NIHL)

13. Acoustic Trauma
◦ Permanent damage to hearing caused by a single brief exposure to
very intense sound ( Impulse Sound)
◦ Ex : Explosions, Gun Fire, Powerful Crackers
◦ These sounds may reach up to 140 to 170 dB sound pressure level
◦ Impulse noise can be as brief as 0.2 ms
◦ This Impulse sound causes
◦ Mechanical damage to organ of Corti,
◦ Tear Reissner’s membrane,
◦ Rupture hair cells and
◦ Allowing mixing of perilymph and endolymph
◦ Tympanic membrane rupture
◦ Disrupt Ossicles

14. Noise Induced Hearing Loss
(NIHL)
 Temporary threshold shift (TTS)
 Impaired Hearing immediately after exposure to Loud
noise
 recovers after few minutes to a few hours even up to 2
weeks.
 TTS depends on the noise - its intensity, frequency and
duration.
 Permanent threshold shift (PTS)
Hearing impairment is permanent and does not recover.

15.  Presbyacusis
 Old age deafness has a cumulative effect
 Tinnitus
 Hyperacusis

16. Noise trauma depends on
1. A frequency of 2000–3000 Hz causes more damage than
other frequencies.
2. Intensity and duration of noise - As the intensity increases,
permissible time for exposure
3. Continuous vs interrupted noise - Continuous noise is more
harmful.
4. Degree of TTS and PTS varies in different individuals.
5. Pre-existing ear disease

17. Pathophysiology
◦ Acoustic overstimulation - excessive release of
neurotransmitters ( Glutamate )
◦ Excessive Glutamate – contribute to NIHL
◦ Sound of high intensity decreases cochlear blood
flow (this is a potential mechanism for cochlear
dysfunction associated with noise exposure)

18. ◦ Exposure to impulse noise for 5 mins - Apoptotic
changes in chinchilla OHC (Outer Hair Cells)
◦ Necrotic change appear on OHC after 30 minutes
exposure
◦ Synaptic connections between the inner hair cells
(IHCs) and spiral ganglion cells are vulnerable to
noise insults

19. MENTAL /PSYCHOLOGICAL EFFECTS
(non auditory effects)
 Lack of concentration.
 Decreased memory.
 Inability to do skilled work/ learning
 Loss of sleep
 Irritability
 Poor academic performance
 Precipitation of Psychiatric illness and Seizure
 Effects on animals and other living or evennon living things.
(eg damage to old buildings)

20. MAX. NOISE STANDARDS
Ambient Air Quality Standards in respect of noise
 Daytime – 6am to 10 pm, Night – 10 pm to 6 am
 Silent zone - Not less than 100 metres around hospitals,
educational institutions, courts or other areas declared
Day Night
A Industrial 75 decibels 70
B Commercial 65 55
C Residential 55 45
D Silent Zone 50 40

21. PERMISSIBLE EXPOSURE IN
CASES OF CONTINUOUS
NOISE
Noise level (dBA) Permitted daily exposure (hrs)
90 8
92 6
95 4
97 3
100 2
102 1.5
105 1
110 0.5
115 0.25

22. ◦ Audiogram - Audiogram may show dip at 4000 Hertz

23. PREVENTION
 Restriction of loud speakers
 Duration / loudness.
 Avoid loud speakers in open spaces
 Crackers
 Time restriction.
 Use of noiseless fire crackers.
 Traffic
 Restrict extra and air horns
 When giving fitness certificate, measure the noise
levels of engines.
 Discourage using horns as much as possible.
 Enforce silent zones strictly.

24. INDUSTRY AND
CONSTRUCTION
 Employees should use ear plugs / ear muffs
 Acoustic barriers
 Maximum sound should be 75 decibels
 Check hearing periodically

25. ◦ As the hearing loss becomes more severe, a hearing
aid takes on an increasingly beneficial role
◦ Tinnitus should be managed as of the overall care
◦ Modern neurophysiological methods (such as
tinnitus retraining therapy) utilize a combination
of cognitive, directive counselling and sound
therapy

26. ROLE OF GOVERNMENT
 Enforce the laws strictly
 Noise pollution (regulation and control) Rules 2000.
 Helpline - officials to take action on public
complaints.
 No amount of legislation will help unless the
public is convinced that noise is a menaceand
takes steps to curb it.

27. THANK YOU
Courtesy:
Shri.Dr Ch Ramanachary ji,
MS ENT
Professor and HOD
Prathima Institute of Medical Sciences
Karimnagar, Telangana State, India