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EN 352-4:2001
Hearing protectors. General requirements Part 4: Level-dependent ear-muffs

This standard requires all of the testing specified in EN 352-1 with the additional clause below tested on additional samples.

Criterion levels

With the hearing protection worn, the external sound pressure level and the level at the ear is measured simultaneously with miniature microphones placed into the ear canals of human test subjects. The criterion level is the external noise level which equates to a level of 85dB(A) at the ear.