NIHL is defined by National Code of Practice (2004) as hearing impairment arising from exposure to excessive noise at work, and is also commonly known as industrial deafness. NIHL is entirely preventable but once acquired it is irreversible

1. NOISE INDUCED HEARING LOSS
(NIHL)

2. Introduction to
NOISE INDUCED
HEARING LOSS
(NIHL)
NIHL is defined by National Code of
Practice (2004) as hearing impairment
arising from exposure to excessive noise at
work, and is also commonly known as
industrial deafness.
NIHL is entirely preventable but once
acquired it is irreversible
Most recent data (2006) suggests that the
number of NIHL represents 19% of all of all
disease-related
claims made and 3.2% of the total disease
and injury related claims.

3. Causes of NOISE
INDUCED HEARING
LOSS (NIHL)
Continuous Noise exposure
The extent of hearing loss increases with
time of exposure, and also increases with
increasing the intensity of sound levels to
which an employee is exposed.
Most scientific evidence suggests that the
hearing loss does not progress once
exposure to noise has discontinued
National Occupational Health and Safety
Commission (NOHSC) standard identifies a
continuous exposure level of 85dB(A) over
8 hrs and a maximum peak exposure level
140 dB(C)

4. Causes of NOISE
INDUCED HEARING
LOSS (NIHL)
Impulsive Noise
Eg Explosions and Gunfire
Very high sound level eg > 140dB ©
Can result in asymmetrical loss
Ototoxicity
Damage usually associated with
combination of ototoxins and noise
Eg butanol, toluene, carbon monoxide,
solvent mixtures and certain types of
medications eg cancer therapy drugs and
asprins

5. Causes of NOISE
INDUCED HEARING
LOSS (NIHL)
Compounding factors
Non-work related
Eg Congenital factors and recreational
noise
Role of cofactors remains poorly
understood
Eg cardiovascular disease, diabetes, and
neurodegenerative diseases

6. Interpreting
Audiograms
Audiograms represent the softest sound a
person can hear.
Conductive loss–outer or middle ear.
Sensorineural loss –inner ear or neural
pathway. Permanent. Often age or noise
related.
Liability usually based upon sensorineural
only
X = left ear. O = Right ear[ or ] denotes bone
conduction

7. Effect of NOISE
INDUCED HEARING
LOSS (NIHL)
NIHLs commonly appear as a sloping loss
that is most prominent in the higher
frequencies (4k)
Effects speech perception by reducing
perception of consonant sounds (p,b,k,s,z etc)
needed for speech clarity.
Vowels usually remain intact as there is often
good residual hearing throughout the lower
frequencies.
Result = clients report that they can hear
people speaking but not understand them –
the vowels come through clearly but the
important consonants are distorted.

8. Progression of
NOISE INDUCED
HEARING LOSS
(NIHL, 25 + years)
Moderate to Profound high
frequency loss
= 67.4% (40yo), 62.5% (70yo)

9. Calculation of
percentage hearing
loss (PHL)
Procedure for determine PHL
1. Establish hearing threshold levels at
defined frequencies: 500Hz, 1000hz, 1500
Hz, 2000 Hz, 3000Hz, 4000Hz
2. Go to look up tables (NAL Report No 118)
for each of the frequencies to determine
percentage hearing loss (PLH) for each
frequency (PLH500, PLH1000…..);
3. Add up all the percentage hearing losses
to give an overall figure
4. Appropriate deductions (if any) made

10. Effect of NOISE
INDUCED HEARING
LOSS (NIHL)
NIHLs commonly appear as a sloping loss
that is most prominent in the higher
frequencies (4k)
Effects speech perception by reducing
perception of consonant sounds (p,b,k,s,z
etc) needed for speech clarity.
Vowels usually remain intact as there is
often good residual hearing throughout the
lower frequencies.
Result = clients report that they can hear
people speaking but not understand them –
the vowels come through clearly but the
important consonants are distorted.

11. Statistics of NOISE
INDUCED HEARING
LOSS (NIHL)
claims
The average cost of workers compensation
claims for NIHL in 2001/2 was calculated to
be $6711.
The average cost of workers compensation
claims for NIHL in 2001/2 was calculated to
be $6711.
This figure does not include Hearing Aid
fittings

12. Prevention NOISE
INDUCED HEARING
LOSS (NIHL)
Noise Control and Hearing Loss Prevention
Program
Actions to reduce noise exposure eg. Noise
insulation, ear protection
Actions to monitor the health of employees eg,
annual hearing screening programs
Establishing a noise control policy and
program
noise control policy and program will enable a
systematic
approach to hearing conservation in a company eg
purchasing policy on equipment noise levels,
mandatory ear protection, training programs for
employees

13. References https://www.hearingsol.com/help/hear
ing-loss/noise/
https://www.hearingsol.com/