Physical predictors for earmuff comfort

This work has looked at selection of hearing protectors for use within the mining industry and has been concerned primarily to identify any relationship between physical characteristics of circumaural hearing protectors (earmuffs) and subjective assessment of comfort and overall acceptance. Twenty-four types were submitted for test and measured for headband force, contact surface area of ear cushions and pressure exerted. This number was reduced to eight by an initial selection procedure based on the above parameters. Ten samples of each type were procured and measured as above with additional measurements of ear cushion compliance and headband force at different headwidths. Subjective assessments of performance were obtained by questionnaire from twenty-seven men involved in underground trials at four collieries. A rank order preference was determined for categories of comfort, convenience, pressure and acceptance. From the measurements obtained it was concluded that a weight per unit pressure ratio was- the best indicator of comfort of a device. In this study, a ratio of approximately 40: 1 was acceptable, with satisfaction declining as the ratio increased. An objective method for measuring attenuation was investigated and a simplified procedure suggested as an in-service monitoring test for deterioration of earmuff performance.