Occupational hearing loss, or damage to hearing in a work environment, can occur from exposure to very loud noise for a short time or prolonged exposure to moderate noise levels.
Some factors, such as exposure to toxic substances or mechanical vibration, may interact with noise exposure to produce hearing loss that is greater than that associated with the combined effects of the individual causes.
This type of testing displays a workers Hearing Threshold Level (HTL) at different frequencies and allows the tester to calculate the magnitude of a worker’s occupational hearing loss.
The World Health Organization defines disabling hearing impairment in adults as permanent Hearing Threshold Level of 41 decibels or greater. At this level of impairment most people can only distinguish words spoken at one metre if they are spoken in a raised voice.
The Standard for Occupational Noise [NOHSC:1007 (2000)] sets the maximum daily occupational noise exposure level at an eight-hour equivalent continuous sound pressure level of 85 dB or a peak sound pressure level of 140 dB1,2. In addition, a code of practice [NOHSC: 2009 (2004)] outlines the noise management program that workplaces need to implement when the National Standard is exceeded.
The preferred solution to excessive noise exposure is to completely eliminate the source of the loud noise. When this is not possible or practical, the legal requirement is to minimise exposure through a hierarchy of controls such as the following1:
- Substitute the noise source with quieter machinery or processes;
- Isolate the noise source from workers;
- Apply engineering solutions (e.g. fit mufflers, redesign the noise source, and install noise guards or enclosures);
- Apply administrative solutions (e.g. schedule noisy work for when fewest workers are present, provide signs and quiet areas for breaks), and when none of the above are reasonably practicable;
- Provide personal hearing protectors (e.g. ear muffs and plugs).
Within this hierarchy, priority is given to the source of the noise, followed by the path of transmission and, as a last resort, the exposed worker. A comprehensive hearing conservation program or noise control program should include strict adherence to the hierarchy of controls as well as assessments of noise exposure and hearing; education with respect to risks, solutions and responsibilities; and training on noise control and personal protection.
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- Safe Work Australia (2010) Occupational Noise-Induced Hearing Loss In Australia: Overcoming barriers to effective noise control and hearing loss prevention.http://www.safeworkaustralia.gov.au/sites/SWA/about/Publications/Documents/539/Occupational_Noiseinduced_Hearing_Loss_Australia_2010.pdf
- Occupational Noise Management Part 2: Noise Control Management AS/NZS 1269.2:2005