Changes in attenuation in personal hearing protector over time during use

Abstract

Ideally, implementing engineering controls reduces workers noise exposures below the permissible exposure level (PEL). However, some occupations continue to have exposures above the PEL. To protect the hearing sensitivity of these workers, personal hearing protectors (PHP) must be worn. Manufacturers test PHPs under ideal conditions in a laboratory. For these tests, highly motivated and trained subjects remain stationary. Furthermore, a researcher helps the subject fit the PHP. Shortly after determining that the PHP was properly fitted, the tests are conducted. Under these conditions the optimum attenuation afforded by the PHP is achieved. Mining conditions differ substantially from those under which the laboratory attenuations are determined. Often, workers wear their PHPs for extended periods without removal. Moreover, a worker’s constant movement may disrupt the seal of a PHP. Once the seal is broken, the PHP provides degraded performance. This project examines any change in earmuff attenuation over a 3-h wearing time in a laboratory. After donning an earmuff unaided, a subject wore the earmuff for 3 h while walking and stopping to lift containers from the floor to a table in a large reverberation chamber. It was found that the PHP’s attenuation did not change substantially during the test.