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| Laboratory evaluation of hearing protection |
Background
Earmuffs, earplugs, and other hearing protectors can be effective adjuncts to noise controls in preventing noise-induced hearing loss, but they have some significant drawbacks. Reported usage rates are below 50%, and those workers who do wear hearing protection typically receive far less noise protection than they might expect. Because of poor fit, real-world protection levels are reported well below 50% of the rated protection determined in the optimal setting of a laboratory. Hearing protectors can also interfere with communication and localization of alarms and important ambient sounds.
To overcome these shortcomings, NIOSH is addressing both hearing protector technology and worker behavior. New research-based guidelines are being developed to match hearing protectors to the noise and task environments without impeding communication. A simplified “roll-pull-hold” technique was developed to make the critical earplug-donning steps easier to remember and perform correctly. An interactive training package for surface drill operators was developed using three-dimensional slides and extensively field tested with workers.
The researchers also investigated improvements to hearing protectors that would make them function better. A special lubricant currently marketed for easing the fitting of hearing aids was evaluated for use with earplugs. Subjects who used the lubricant were significantly more likely to obtain a good protective seal with their earplugs. Also, a new hearing protector technology with a built-in electronic dose and exposure feedback system was subjected to laboratory trials. The system uses inexpensive microphones built into the hearing protectors, and these were found to provide a useful approximation of the amount of hazardous noise reaching the user.
Potential Outcome
Research on improved training and hearing protector technologies was completed in 2005, and follow-on studies to evaluate peer feedback training will be complete in 2007. Beginning in 2003 and continuing through 2008, the results of these studies are being disseminated in a series of practical training products in print, video, and Web format. Hearing protector communication guidelines will be distributed as a Web-based decision tool that will help optimize the match between protectors and different work settings. These products will have an impact on the estimated 90% of miners and drill workers who need to wear hearing protection during at least part of their working shifts. By implementing the training and protector modifications and improving protector usage rates and effectiveness, workers will significantly reduce their exposure to noise. For instance, the roll-pull-hold technique alone achieves 9 dB of improved protection that, if adopted industry-wide, would substantially reduce the incidence of noise-induced hearing loss.