Noise induced hearing loss nihl
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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)

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Noise induced hearing loss nihl

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

Introduction to 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.


Causes of nihl

Causes of 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

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)


Causes of nihl1

Causes of NIHL

Impulsive Noise

Eg Explosions and Gunfire

Very high sound level eg > 140dB (c)

Can result in asymmetrical loss

Ototoxicity

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


Causes of nihl2

Causes of NIHL

Compounding factors

Non-work related

Eg Congenital factors and recreational noise

Role of co-factors remains poorly understood

Eg cardiovascular disease, diabetes, and neurodegenerative diseases


Interpreting audiograms

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


Effect of nihl

Effect of 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.


Progression of nihl 0 5 years

Progression of NIHL ( 0 – 5 years)

Normal Hearing

= 0%

Mild high frequency loss

= 4.6% (40yo), 0% (70yo)


Progression of nihl 10 20 years

Progression of NIHL (10 – 20 years)

Moderate to severe high

frequency loss

= 23.8% (40yo), 18.9 (70yo)

Moderate high

frequency loss

= 16.8% (40yo), 11.9 (70yo)


Progression of nihl 25 years

Progression of NIHL (25 + years)

Moderate to Profound high

frequency loss

= 67.4% (40yo), 62.5% (70yo)


Calculation of percentage hearing loss phl

Calculation of percentage hearing loss (PHL)

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.


Calculation of percentage hearing loss phl1

Calculation of percentage hearing loss (PHL)

Deductions from PHL

1. Asymmetrical hearing loss

Noise Ordinarily effects both

Ears equally.

? – shooter

- tumor

= 21.2%

= 16.8% (using L levels for R)


Noise induced hearing loss nihl

Calculation of percentage hearing loss (PHL)

Deductions from PHL (cont’d)

2. Non-sensorineural hearing loss

= 61.7 %= 16.9%


Noise induced hearing loss nihl

Deductions from PHL (cont’d)

3. Age related hearing loss (presbyacusis)

= 23.8% (40yo),

= 18.9 (70yo)


Noise induced hearing loss nihl

  • Other possible deductions

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.


Statistics of nhil claims

Statistics of NHIL claims

Table 1. Comparison of Comparison of Workers’ Compensation Arrangements.


Statistics of nhil claims1

Statistics of NHIL claims

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)


Statistics of nhil claims2

Statistics of NHIL claims

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%


Statistics of nhil claims3

Statistics of NHIL claims

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


Prevention nihl

Prevention 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


Services provided by hearing matters

Services provided by Hearing Matters

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


Hearing aids

Hearing Aids

  • CIC: Mild – Moderate

  • ITC: Moderate

  • BTE: Moderate-Severe

  • Open-Fit: Mild – Severe


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