Measurements of acoustics properties for level-dependent ear-muffs

The aim of this paper is to present methods of acoustic
measurements of level-dependent ear-muffs with an electronic sound restoration
system switched off and on, according to EN 352-4. Measurements of sound
attenuation and H, M, L criterion levels were carried out for a model of a
level-dependent earmuff. The acoustic properties of test sites, sound field
requirements and test signals are discussed. Measurements of sound attenuation
were carried out in a chamber for testing hearing protectors. The chamber
fulfilled the requirements of PN-EN 24869-1. Measurements of the H, M, L
criterion levels were carried out in a reverberation room where the sound field
of the test site complied with the requirements specified in ISO/DIS 11904-1.
Both the chamber for testing hearing protectors and the reverberation room are
the part of the laboratory of noise in the Central Institute for Labour
Protection in Warsaw, Poland.