Ear Plug Fit and Attenuation - An Experimental Study

Ear canal properties and noise attenuation were studied for 95 young men (conscripts). The ear canal diameter was first measured. Then the direct objective noise attenuation was measured with a miniature microphone inserted between the ear drum and an ear plug. The men were allowed to choose both the best and worst attenuating and best and worst fitting ear plug of the five alternatives. The noise attenuation was very similar with the different ear plugs. However, the measurements of 9% of the subjects showed noise attenuation of less than 15 dB, and this range of attenuation indicates a risk of hearing loss when blanks are shot with assault rifles and in exposure to any kind of large calibre weapon noise. The best ear plugs were the Ear Classic and the Bilsom 303. Conscripts need training in inserting ear plugs, and men with unsuitable ear canals must be excluded if ear plugs are to be used in critical noise environments.