PURPOSE:  To develop recommendations and strategies for mine operators and mineworkers that will improve the audibility of spoken communication and hazard/warning signals in the mining environment while preventing additional cases of noise-induced hearing loss.

RESEARCH SUMMARY:  Hearing protection devices are still needed in many settings where engineering and administrative controls are insufficient to reduce noise to a safe level. However, workers have reported significant concerns about the diminished audibility of speech, machine alarms, and other important sounds that result from wearing standard hearing protectors. By addressing this concern, this study will encourage the use of hearing protection in ways that minimize audibility problems.

There are hundreds of different hearing protectors on the market, including standard earmuffs, earplugs, and sophisticated electronic designs. Every protector has a different effect on the types of sounds they allow to reach the wearer’s ears, and the spatial cues they provide about the location of sound sources. Current research is quantifying these effects so appropriate recommendations can be made for different occupational noise environments.

Along with standard hearing protectors, new technological approaches to protection and exposure reduction are also being investigated. For instance, extensive laboratory evaluations of protectors that use electronic systems to pass selected sounds through the protector are being performed. A system that uses microphones inside the protector to provide feedback about the noise levels that actually reach the wearer’s ears was also recently evaluated. In general, the microphone placements used in this system potentially provided a usable approximation of the wearer’s true dosage.