The aim of occupational audiology is to prevent hearing loss caused by occupational sound exposure which can exacerbate the long-term effects of central presbyacusis as employees age. To provide the best noise protection over time, research suggests that best practice should be to attempt to limit sounds at the eardrum to 75-80dBA. Attenuation of sound by 10-15dB through earplugs should be sufficient to achieve this. Practical fit testing and counselling is required in order to obtain optimum hearing protection because although earplug manufacturers give noise reduction ratings for their products, this does not correlate the actual protection delivered when in use. The other benefit of proper fit testing is that it can be used to identify unusual configurations of ear canal anatomy which may result in incompatibility with certain earplugs. Low tone attenuation of >20dB must also be tested for separately to detect slit leak venting, as well as interaural performance difference. Three quarters of the earplug length should fit snugly and deeply into the ear canal with a deep seal, without significant slit leak and should not move outwards with temporomandibular joint movement, nor be able to be removed easily. Sound protection must be optimised for each individual employee as best possible in order to prevent hearing loss and to promote better lifelong hearing for all. 

Fit for hearing protection with earplug testing.
Colucci D.
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Linnea Cheung

Frimley Park Hospital, Surrey, UK.

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