Noise-induced hearing loss (NIHL) can occur from acute acoustic trauma due to a one-time exposure to loud sounds like explosions or from gradual exposure to excessive noise in workplaces or entertainment venues. NIHL damages the delicate hair cells in the cochlea leading to permanent hearing impairment that cannot be repaired. Audiometric testing reveals a characteristic notch pattern at 3-6 kHz frequencies and a history of noise exposure is required to diagnose NIHL. Prevention involves engineering controls to limit noise levels, proper use of ear protectors when exposed to sounds over 85 dB, and hearing conservation programs for workers.

1. Noise-Induced Hearing Loss
4TH YEAR PRESENTATION.

2. Noise-induced hearing loss
 Noise-induced hearing loss (NIHL) is hearing impairment resulting from exposure
to high decibel sound
 Dependent on following features of sound;
- intensity
-duration
-type of noise exposure

3. Types of NIHL
 Acute acoustic trauma:
NIHL caused by acute acoustic trauma refers to
permanent cochlear damage from a one-time exposure to an excessive sound
pressure. E.g. explosions, gunfire, drum hit loudly, firecracker.
 Gradual developing NIHL:
Gradual developing NIHL can be caused
by multiple exposure to excessive noise in the workplace or repetitive, frequent
exposures to sound of excessive volume like home and vehicle stereos, nightclubs,
concerts, mining and construction etc.

4. General estimates of work related noise

5. Cont..
 2nd most common sensorineural hearing loss, after presbycusis.
 Sounds exert shearing force of cilia of hear cells lining the the basilar
membrane of cochlea
- when excessive= metabolic overload, cellular
damage and death
-damaged cochlea cannot be repaired.
-once removed from damaging noise, no further
progression of NIHL.

6. ..

7. Effects of Noise on hearing.
 Temporary Threshold Shift;
may occur suddenly after exposure
to a high level of noise. Results in temporary hearing loss.
 Permanent Threshold Shift;
ability to hear is reduced
permanently, causing a permanent hearing loss.

8. Sign and symptoms.
 Gradual loss of clarity in perceived speech, often attributed to
inattention or person not speaking clearly.
 Difficulty in hearing high-frequency sounds of speech
 Difficulty in understanding others in crowd.
 High pitched tinnitus.

9. Audiometric testing.
 Hearing loss: measured by determining auditory threshold
(sensitivity) at various frequencies.
 No loud noise exposure for at least 16 hours prior to the
testing (to avoid temporary lowering of hearing threshold.
 A loss of less the 20 db can be considered normal.
 Bilateral notch in hearing 3,4 or 6kHz

10. How to diagnose NIHL?
 Typical pattern of NIHL on audiometry.
 History of noise exposure
 Absence of other conditions causing hearing loss;
-hearing loss associated with presbycusis or
ototoxic agents.
-determining degree of impairment due to
aging.

11. Prevention.
 Engineering control
 Ear protectors (must be used continuously)
 When workers are or maybe exposed to noise more than 85db, then they must;
-measure the daily noise exposure
-identify significant source of noise
-change the equipment to reduce noise
-go for hearing conversation program
-use ear protectors (earplugs, ear muffs)
- one should not be exposed to voice greater than 110db for more
than 0.5 hours per day without ear protection.

12. Audiogram

13. Ear protectors

14. Hearing aid

15. ..