Real world attenuation measurements were carried out to determine the effectiveness of hearing protection devices in various industrial enterprises in Germany. The study aimed at establishing which models of earplugs and earmuffs resulted in the greatest deviations, so that the protective effect could be increased through improved occupational safety requirements, improved instructions for use, training, and regular health examinations. Sound attenuation measurements were conducted using a computer controlled single channel electroacoustic system with third octave bands of noise as test sounds, in six branches of industry. Sound attenuation in the field were compared with laboratory measurements. Results showed that for earmuff protectors, differences in the mean were only 2.3 to 5.7 decibels (dB). Individual subjects reproduced the high values known from laboratory measurements. For earplugs, the mean difference for the foam plug was 13.3dB, a result that could be reproduced in the laboratory if subjects were instructed to insert the earplug just far enough into the ear canal that it did not fall out of the ear. For earplugs made of glass down attenuations were 5.9 to 8.7dB. How earplugs were worn also determined sound attenuation and, when correctly worn, at a frequency range of 500 to 8000 Hertz, mean improvement was 4.8dB for the glass down earplug, and 3.8dB for the foam type. The effect of aging on earmuffs was studied on 16 subjects. Results showed that duration of use, especially with hardening of cushions, decreased effectiveness. The author concludes that two new safety requirements are necessary in developing International Standards for hearing protectors. Lists of protective measures for two groups of noise exposed persons, workers with normal audiometric results in preventative occupational safety tests, and those tested to be at risk for noise induced hearing loss were presented.
Proceedings, 1992 Hearing Conservation Conference, April 1-4, 1992, Lexington, Kentucky, Office of Engineering Services, University of Kentucky and NIOSH