From the Guidelines
An area should be designated as a hearing protection zone when noise levels reach or exceed 85 decibels (dB) averaged over an 8-hour workday. This threshold is crucial because prolonged exposure to noise above 85 dB causes permanent hearing loss through damage to the delicate hair cells in the inner ear, which cannot regenerate once destroyed 1. The risk of hearing damage increases significantly with both noise intensity and duration of exposure. For every 3 dB increase above 85 dB, the safe exposure time is cut in half - meaning at 88 dB, protection is needed after just 4 hours, and at 91 dB, after only 2 hours.
Key Considerations for Hearing Protection Zones
- Noise levels exceeding 85 dB averaged over an 8-hour workday necessitate the provision of hearing protection equipment such as earplugs or earmuffs to workers.
- Areas with impulse or impact noise exceeding 140 dB peak sound pressure level should always be designated as hearing protection zones regardless of duration.
- Proper signage should clearly mark these zones.
- Hearing conservation programs should include regular noise monitoring, audiometric testing for workers, and training on the correct use of hearing protection devices.
Importance of Prevention
As highlighted in recent studies, the prevention of occupational noise-induced hearing loss (NIHL) is a priority due to its irreversible nature 1. The use of engineering and administrative controls, hearing protection devices, and the monitoring of hearing with audiometric testing are essential components of effective hearing conservation programs. Given that the incidence of occupational NIHL remains high, placing it among the most common occupational disabilities worldwide, stringent measures to protect workers' hearing are imperative.
From the Research
Designation of Hearing Protection Zones
To determine the noise levels at which an area should be designated as a hearing protection zone, we need to consider the potential risk of noise-induced hearing loss.
- The studies 2, 3 suggest that exposure to noise levels above 85 dB(A) can increase the risk of hearing loss.
- A study 4 found that the median LAeq,8h was 94.1 dB(A) and the median unadjusted cumulative noise exposure was 102.3 dB(A)·year, which can lead to noise-induced hearing loss.
- Another study 5 states that long-term exposure to a noisy environment can cause permanent hearing impairment.
Noise Levels for Hearing Protection
Based on the available evidence, the following noise levels can be considered for designating an area as a hearing protection zone:
- 85 dB(A) or above, as exposure to noise levels above this threshold can increase the risk of hearing loss 2, 3.
- 94.1 dB(A) or above, as this is the median LAeq,8h found in a study of workers exposed to noise 4.
Importance of Hearing Protection
It is essential to note that hearing protection devices can reduce the risk of noise-induced hearing loss, but their effectiveness depends on proper use and training 2, 3, 4.
- A study 4 found that the median Personal Attenuation Rating (PAR) was 13.0 dB, and the median PAR' (the PAR after combining the earplugs usage time) was 8.0 dB.
- Proper use of hearing protection devices can reduce the risk of hearing loss, and it is recommended to wear them consistently in the workplace 4.