Occupational Noise‑Induced Hearing Loss (ONIHL) is a permanent yet preventable condition caused by prolonged exposure to hazardous noise levels in the workplace. It remains a significant occupational health risk, particularly in industries where loud machinery, tools and equipment are used regularly.
What causes ONIHL
ONIHL develops when repeated exposure to excessive noise damages the sensitive structures of the inner ear. The likelihood and severity of hearing loss depend on the level and duration of noise exposure and how effectively risks are controlled. Once this damage occurs, it is irreversible, making prevention and early detection essential.
Symptoms of ONIHL
Early symptoms may include difficulty hearing high‑frequency sounds, ringing in the ears (tinnitus) and problems understanding speech in noisy environments. Because these changes often occur gradually, hearing loss may go unnoticed until it becomes more pronounced.
Who is most at risk
Workers in industries such as manufacturing, construction, mining, agriculture, transport, local government and entertainment are at higher risk due to regular exposure to hazardous noise. Risk increases with higher noise levels, longer exposure times and inconsistent use of effective hearing protection.
Current requirements for employers
Where workers are frequently required to use hearing protection because workplace noise exceeds exposure standards, employers must provide audiometric (hearing) testing. This includes a baseline hearing test within three months of commencing noise‑exposed work, followed by repeat testing at least every two years, or more frequently where higher noise exposures exist. Hearing protection alone is not sufficient — employers must actively monitor hearing health and the effectiveness of noise controls.
Noise exposure standards
The workplace noise exposure standard is an average of 85 dB(A) over an eight‑hour workday, or a peak noise level of 140 dB(C). Where these levels are exceeded and hearing protection is used as a control measure, audiometric testing is required.
What audiometric testing involves
Audiometric testing is a painless, non‑invasive hearing assessment that measures how well a person hears sounds at different frequencies and volumes. A baseline test establishes a worker’s hearing level, with follow‑up tests used to identify any changes over time and assess whether existing controls remain effective.
Prevention and management
Preventing ONIHL involves reducing noise at the source where possible, managing exposure through workplace controls and ensuring hearing protection is used correctly. While ONIHL cannot be reversed, early identification through regular hearing testing can prevent further deterioration and support long‑term hearing health.
How IMMEX can help
IMMEX assist organisations meet compliance with current legislative requirements, identify hearing risks early and protect the long‑term hearing health of their workforce.
IMMEX can assist with audiometric testing as per the AS/NZS 1269.4:2014 standard.
IMMEX is also able to assist with ongoing serial audiometry for monitoring and follow-up.
For more information about our pre-employment and other medical assessments, please contact us.