ISO/TR 4869-4:1998 PDF

This Technical Report specifies a physical test method for level-dependent sound-restoration ear-muffs. The physical measurements are made with the acoustic test fixture (ATF) according to ISO/TR 4869-3 or with a suitable head and torso simulator (HATS) with a suitable acoustic isolation (see clause 7). The results of these tests in combination with the results from the ISO 4869-1 tests can be used to estimate the effective A-weighted sound pressure level when sound restoration ear-muffs are worn.

The method described is not suitable for measurement of the effective sound pressure level under ear-muffs in the case of impulsive noise nor for active noise reduction ear-muffs.