The Ambient Noise Floor in an Earcup of a Hearing Protector Worn by a Human Subject.
Am Conf of Gov Ind Hyg Cincinnati Ohio, 1986 14:557-563
Hearing protective devices (hpd's) are necessary to control the noise exposure of miners when noise levels are in violation of federal regulations and engineering or administrative controls cannot be implemented. However, standard laboratory performance measurements appear to overestimate the amount of protection a working miner may receive from hpd's. To more effectively evaluate hearing protector performance, the Bureau of Mines is investigating the basic parameters that influence the noise-attenuating properties of hpd's. Those parameters are being identified, and the degree to which they can be controlled under experimental conditions in the laboratory and field is being evaluated. With reasonable control over the stimulus and experimental parameters, it was possible to use a physical measurement procedure to predict the standard psychophysical method of evaluation in the laboratory. In attempting to adapt the method for use in the field, a high ambient noise level under the muff was observed. An experiment was designed to confirm and quantify the ambient noise level under an earmuff worn by a human subject. Preliminary analyses of the data tend to attribute the presence of the noise floor to human respiration and pulse. A discussion of the methods, results, and implications as to the effect of the noise floor on the physical measurement procedure will be presented.
Am. Conf. of Gov. Ind. Hyg., Cincinnati, OH, V. 14, 1986, PP. 557- 563