So, you have predicted that the hearing protection worn by staff in your workplace provides the correct amount of attenuation, but what happens if these devices are removed even for a short period of time whilst in a high noise environment? How does it impact the hearing protector’s effective attenuation?
If a hearing protector is not worn for 100% of the time in a noisy environment, then its effectiveness decreases rapidly. The graph below shows the reduction in effectiveness of a hearing protector that is removed for a period of time expressed as a percentage of the total time that the user is exposed to the noise. Three different hearing protectors each of varying degrees of protection are represented in the graph.
When all 3 hearing protectors are worn for 100% of the exposure time the effective attenuation is as predicted (i.e. 30dB, 20dB, and 10dB respectively for all 3 of them). However, if the 30dB rated hearing protector is worn for 98% of the exposure time (or removed for 2% of the time), then the effective attenuation drops by approximately 12dB. As an example, for a noise exposure period of 8 hours, this would imply that removing a 30dB attenuation rated hearing protector for nearly 10 minutes would give only about 18dB of hearing protection!
By comparison, the drop in effective attenuation is only 1dB to 2dB when the lowest rated hearing protector (offering 10dB protection) is removed for 2% of the time that the wearer is exposed to noise.
When all the 3 types of hearing protectors are unworn for 50% of the noise exposure time, then the effective attenuation is 3dB only for all of them.
Another surprising observation as you can see in the graph below, is that the hearing protector offering 10dB of attenuation, if worn (correctly and consistently) for 100% of the time, will provide just as much protection as both the potentially more expensive 20dB and 30dB rated hearing protectors worn for 90% of the time (for an 8 hour noise exposure period, this is equivalent to not being worn for 48 minutes).
The important lesson is…
Employees must understand the importance of wearing hearing protection before entering an area of high noise, and that when hearing protection is removed even briefly whilst in noisy environments, the effectiveness of the hearing protector can be severely reduced. This attaches great significance to selecting comfortable hearing protection (appropriately rated, of course) as the temptation to remove it is substantially reduced. Giving employees a choice of protectors also helps with wearer compliance.
Essel Acoustics has the expertise to carry out full and competent noise risk assessments in your workplace and can recommend appropriately rated hearing protection if its use cannot be avoided. Contact us for any assistance on this.
Download a free guide to see what a good noise risk assessment must consist of. This guide also explains why overprotective hearing protection can be hazardous in the workplace. Click here to receive the guide.