Preventing noise-induced hearing loss (NIHL)
Approximately 16% of disabling hearing loss in adults is attributed to workplace noise.[1] Noise-induced hearing loss (NIHL) may develop suddenly following exposure to very loud sounds, but often damage occurs slowly over a period of many years.
To prevent NIHL, it is vital to understand how workplace noise can cause hearing loss and what steps to take to protect employees.
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How does noise-induced hearing loss (NIHL) develop?
Exposure to dangerous noise levels damages the Corti, an organ located in the inner ear. Hair cells within the Corti convert sound waves into nerve impulses, acting as the receptors for our hearing. When these cells are damaged sounds become distorted and may not be sent to the brain.
Damage to the Corti may be temporary. After exposure has ended, the Corti begin to recover. Temporary threshold shift is a type of temporary hearing loss that makes sounds below a certain level inaudible for a period of time following exposure to noise. However if someone is exposed to harmful noise on a regular basis, the ears cannot return to a healthy state which results in permanent hearing loss.
The point at which noise becomes harmful is determined by the decibel level and exposure time. Short-term exposure to extremely loud noises, such as an explosion, can cause immediate permanent hearing loss. Often though NIHL has a long latency period, with exposure occurring regularly over a period of many years.
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Controlling workplace noise
Employers have a legal responsibility to control workplace noise. Exposure limits set maximum noise levels that must not be exceeded, with other action values requiring employers to take certain steps to protect employees’ hearing.
Workplace noise should be eliminated or reduced at source before requiring the use of personal hearing protection. Beginning in the planning stages, aim to eliminate or substitute noisy tasks, and select low-noise equipment. Set up the workplace to manage noise exposure, designating hearing protection zones to isolate noise within specific areas.
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Hearing protection
After implementing other control measures, personal hearing protection can be used to reduce residual noise to a safe level. When selecting hearing protection, aim to achieve an average exposure of 80 dB for the wearer. Noise exposure limits and control requirements vary by region – make sure to check local legislation before selecting hearing protection equipment.
Choose a hearing protector that provides adequate attenuation without overprotecting the wearer. The highest SNR level is not necessarily best – if the attenuation level is too high, the wearer may not be able to hear important warning sounds such as alarms and approaching vehicles.
Hearing protectors need to be correctly fitted, well-maintained and compatible with other equipment. Mounted ear defenders must be tested and certified with helmets and faceshields to verify compatibility.
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Working in a noisy environment increases the risk of NIHL. Regular exposure to harmful noise levels over a period of many years causes permanent hearing damage, even though the effects may not be noticed at the time. To protect employees, it is vital to reduce workplace noise exposure by implementing effective control measures and providing appropriate personal hearing protection.
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[1] World Health Organization, World Report on Hearing, 2021