NS EN ISO 4869-4 : 1ED 2000

Specifies a physical test procedure for level-dependent sound-restoration ear-muffs. The physical methods are made with the acoustic test fixture (ATF) according to ISO/TR 4869-3 according to ISO/TR 4869-3 or with a suitable head and torso simulator (HATS) with a suitable acoustic isolation. The test results can be used in conjunction with the results from the ISO 4869-1 tests to estimate the effective A-weighted sound pressure level when sound restoration ear-muffs are worn. Not suitable for measurement of the effective sound pressure level under ear-muffs in the case of impulsive noise or for active noise reduction ear-muffs.