by Marshall Chasin
Whenever one measures the attenuation of hearing protection, it is different for every frequency. This has to do with the rule of acoustics – generally lower frequency, longer wavelength sounds do not “see” an ear obstruction such as an earplug or earmuff as well as the higher frequency, shorter wavelengths. Subsequently, lower frequencies have relatively little attenuation (typically no more than 25 dB at 250 Hz) whereas higher frequency sounds can be reduced by 30-35 dB. Having a single number to represent this non-uniform attenuation is like saying that a person with a mild to moderate sloping audiogram has a 20 dB (or should it be 60 dB?) hearing loss.