NOISE INDUCED HEARING LOSS (NIHL). SISA PRESENTATION DECEMBER 2007. Based on The Australian Safety and Compensation Council (ASCC) WORK-RELATED NOISE INDUCED HEARING LOSS IN AUSTRALIA (APRIL 2006). BY JASON SPARNON, AUDIOLOGIST & JAN MACHOTKA, AUDIOLOGIST. Introduction to NIHL.
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NOISE INDUCED HEARING LOSS (NIHL)
Based on The Australian Safety and Compensation Council (ASCC) WORK-RELATED NOISE INDUCED HEARING LOSS IN AUSTRALIA (APRIL 2006)
BY JASON SPARNON, AUDIOLOGIST & JAN MACHOTKA, AUDIOLOGIST
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.
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
Greatest amount damage occurs in the first 10-15 years
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)
Eg Explosions and Gunfire
Very high sound level eg > 140dB (c)
Can result in asymmetrical loss
Exposure to chemicals containing ototoxins
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
Eg Congenital factors and recreational noise
Role of co-factors remains poorly understood
Eg cardiovascular disease, diabetes, and neurodegenerative diseases
X = left ear. O = Right ear
[ or ] denotes bone conduction
Mild high frequency loss
= 4.6% (40yo), 0% (70yo)
Moderate to severe high
= 23.8% (40yo), 18.9 (70yo)
= 16.8% (40yo), 11.9 (70yo)
Moderate to Profound high
= 67.4% (40yo), 62.5% (70yo)
Procedure for determine PHL
1. Establish hearing threshold levels at defined frequencies: 500Hz, 1000hz, 1500Hz, 2000Hz, 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
5. This % hearing loss (PLH) determined is used for compensation claims.
Deductions from PHL
1. Asymmetrical hearing loss
Noise Ordinarily effects both
? – shooter
= 16.8% (using L levels for R)
Calculation of percentage hearing loss (PHL)
Deductions from PHL (cont’d)
2. Non-sensorineural hearing loss
= 61.7 %= 16.9%
Deductions from PHL (cont’d)
3. Age related hearing loss (presbyacusis)
= 23.8% (40yo),
= 18.9 (70yo)
4. Pre-employment hearing loss and Congenital hearing loss
5. Non-work related medical conditions eg diabetes
6. Recreational noise exposure
7. Evidence suggests that noise exposure alone does not usually produce a loss greater than 75 dBHL at high frequencies, and 40 dBHL at lower frequencies.
Table 1. Comparison of Comparison of Workers’ Compensation Arrangements.
Table 2. Number of Claims for NIHL
Claims in SA decreased from 370 in 1999 to 190 in 2002
Although the number of NIHL claims has been reduced, it does not mean that noise induced deafness in Australia has been reduced
*most recent data available (2006)
Figure 1. NIHL Claims per Exposed Employees (2001/2)
Number of claims per hundred thousand employees
The highest number of claims are made by: Labourers and related workers, 33% Tradespersons and related workers, 30% Intermediate production & transport workers (plant or machine operators or transport drivers),25%
The average cost of workers compensation claims for NIHL in 2001/2 was calculated to be $6711.
Therefore, for Australia, the direct cost of NIHL claims for 2001/2 is calculated to be $6711 x 4510 claims i.e. just over $30 million.
This figure does not include Hearing Aid fittings
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
Who is Hearing Matters
3 audiologists – Jan, Tara, Jason
Only independent clinic owned by its audiologists
NOT aligned by any hearing aid manufacturer
NOT solely a hearing aid clinic – also diagnostic clinic
Determination of NIHL percentage and diagnostic reports.
Referrals to ENT specialists when appropriate
Hearing aid fittings and tinnitus treatment when appropriate
Noise protection equipment