Noise Attenuating Properties of Earmuffs Worn by Miners. Volume 2. Development of a Laboratory Procedure for the Physical Measurement of Earmuff Attenuation

摘要

The purpose of this study was to develop and evaluate, in the laboratory, instrumentation and procedures that might allow for the use of physical measurements of earmuff attenuation that would yield results equivalent to those obtained from psychophysical measures of attenuation. The ultimate goal was to evaluate techniques that might subsequently prove feasible for physical measurement of earmuff attenuation in the field. Instruments currently in use were modified to have a response similar to differences observed in earmuff attenuation as observed in volume 1 of this report. Mining noise spectra were selected and presented to a single subject seated in a diffuse noise field wearing one of the muffs evaluated in the earlier study and fitted with two physical sound measurement systems. A linear system measured the outside noise level and a linear system plus c correction filter measured the inside noise level. The measurements indicated that under the procedures presented in this report, a laboratory method for measuring earmuff attenuation is feasible and yields results comparable with an extensive psychophysical procedure.