Efficiency of ear protectors in laboratory and real life tests.

The effectiveness of ten different ear-protectors (6 types of earmuffs and 4 types of earplugs) has been tested under laboratory conditions and in the real occupational environment. Three methods were used: (1) physical, utilizing a dummy head; (2) subjective, real-ear, executed on trained human subjects; (3) subjective, measuring TTS2 resulting from occupational, one-workday exposure. It could be shown that the ear protection efficiency ascertained on the basis of TTS2 measurements on workers exposed to noise in their occupational environment is, in nearly all cases, smaller than the efficiency expected, taking into account the sound damping of the same protectors, tested under laboratory conditions, using the physical or real-ear method. Measurements of TTS2 were found to give the best data needed to define the protectors' efficiency, since they include, simultaneously, the impact of various environmental factors, the subjective reactiveness, the nature of the professional task and the acoustical features of the protector used. Therefore this method enables the estimation of the real protection given to workers with a risk of noise-induced hearing loss.