Field investigations of noise reduction afforded by insert-type hearing protectors.

NIOSH conducted field investigations in 1977 and 1981 to determine the actual noise reduction afforded to industrial workers who used insert-type hearing protectors (earplugs) daily. In-situ attenuation tests of 420 workers at 15 industrial plants were conducted to determine the noise reduction provided by earplugs as they were worn during the workday. The workplace results, when compared to manufacturers' best-fit laboratory test results, indicated that 50% of the workers tested were receiving less than one-half the potential attenuation of the earplugs.