Measuring Levels of Hearing Protection

Understanding when to use Hearing Protection

Although there are other methods for assessing the effectiveness of hearing protection for the worker, the most widely used is that of octave analysis. When measuring noise for an assessment of hearing damage/prevention to a worker it is best to use the A weighting filter in conjunction with octave analysis, as it is easier to see which frequencies contribute most significantly to the A weighted Lp.

It is normal for hearing protection manufacturers to quote the octave band attenuation of their devices, typically in the eight octave bands 63Hz, 125Hz, 250Hz, 500Hz, 1kHz, 2kHz, 4kHz and 8kHz. They may quote the APL (Assumed Hearing Protection Level) for each frequency. The APL is commonly acknowledged to be:

APL = Mean Value – 1 Standard Deviation

For example, the Bilsom 727 hearing defenders have the following data:

Frequency (Hz)631252505001K2K4K8K
Mean Value (dB)16.813.919.929.735.835.935.937.4
Standard Deviation (dB)2.93.32.92.92.92.23.94.4
Assumed Protection (dB)13.910.617.027.033.033.836.133.1

Companies and employers are required to supply hearing protection to employees when required either as an addition to noise control measures or when controlling noise measures are being implemented. Hearing protection should not be used as an alternative to noise control.

Employers must supply suitable hearing protection when requested and work with employees to ensure hearing protection is worn in areas of high noise exposure. Noise surveys must be carried out to find the appropriate zones and areas of noise.

Hearing protection should be used to reduce levels of noise which employees encounter, preferably to levels below 85dBA. The large range of protection available can cover all areas of work and provide comfort, including simple in-ear noise protectors and noise excluding headphones which can be worn with other safety equipment such as hard hats, eye protection or dust masks.

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