Noise induced hearing loss is a significant risk factor in many workplaces in Perth and WA.
As noise induced hearing loss can happen over time without the normal signs of an injury such as pain or blood, the only reliable strategy for preventing ongoing injury to workers and to reduce the risk of potential compensation claims is to compare hearing test results over time. Minimising noise and reducing an employee’s exposure to noise are also excellent strategies to minimise risk but only regular (annual or at least every 2 years) hearing tests will tell you if any of your strategies are being effective.
The results of a hearing test, or audiometric test, are recorded on an audiogram. An audiogram is used to chart the results according to loudness (dB) and pitch (Hz).On an audiogram, noise induced hearing loss (NIHL) will usually be seen first as a slight loss of hearing in the 4 kHz region. This dip in hearing is more commonly known as a ‘notch’ in the audiogram. This is recognized on an audiogram as a notch centered around 4000 Hz and it is the characteristic audiometric pattern of early NIHL. Threshold shifts in the 3-6kHz frequencies indicate a hearing loss in the upper part of the frequency range for human voices (Nelson et al. 2005).
If exposure is continued, the notch gradually deepens and widens. Eventually, retention of good hearing in the higher frequencies is lost, and the resulting hearing loss appears only as a relatively steep high-frequency loss beginning at 3000 Hz and becoming more severe at each higher frequency over a period of many years. Persistent noise exposure progressively encroaches on the middle frequencies. In the most severe cases, even the lower frequencies may eventually become involved.
To identify NIHL (noise induced hearing loss) on an audiogram you can look at the shape of the graph. When NIHL occurs the graph shape will often be like a hillside – the steeper the hill the worse the loss. In WA, workers can be legally compensated when the change from their baseline hearing test (first hearing test registered with WorkCover WA) reaches 10%.
Learn more about this from WorkCover WA, who govern workers compensation in WA.
When did you have your last noise survey conducted?
Burden of noise induced hearing loss
Exposure to noise in the workplace, also known as ‘occupational noise’ has been estimated to account for about 10% of the burden of adult hearing loss in western countries (Dobie 2008; Nelson et al. 2005). In the five years between July 2002 and June 2007 there were about 16 500 accepted workers’ compensation claims in Australia for deafness due to exposure to noise. About 99% of these claims were associated with long-term exposure.
Over these five years, the manufacturing, construction and transport and storage industries accounted for 65% of claims. In the financial year 2006–07, the mining, electricity/gas/water supply, and construction industries had the highest claim rates, with 1.8, 1.7 and 1.3 claims per 1000 workers, respectively. In that year, males aged 55–64 years accounted for almost 50% of accepted claims.