Abstract
The purpose of this study was to identify any differences between speech intelligibility measures obtained with MineEars electronic earmuffs (ProEars, Westcliffe, CO, USA) and the Bilsom model 847 (Sperian Hearing Protection, San Diego, CA, USA), which is a conventional passive-attenuation earmuff. These two devices are closely related, since the MineEars device consisted of a Bilsom 847 earmuff with the addition of electronic amplification circuits. Intelligibility scores were obtained by conducting listening tests with 15 normal-hearing human subject volunteers wearing the earmuffs. The primary research objective was to determine whether speech understanding differs between the passive earmuffs and the electronic earmuffs (with the volume control set at three different positions) in a background of 90 dB(A) continuous noise. As expected, results showed that speech intelligibility increased with higher speech-to-noise ratios; however, the electronic earmuff with the volume control set at full-on performed worse than when it was set to off or the lowest on setting. This finding suggests that the maximum volume control setting for these electronic earmuffs may not provide any benefits in terms of increased speech intelligibility in the background noise condition that was tested. Other volume control settings would need to be evaluated for their ability to produce higher speech intelligibility scores. Additionally, since an extensive electro-acoustic evaluation of the electronic earmuff was not performed as a part of this study, the exact cause of the reduced intelligibility scores at full volume remains unknown.
Highlights
Hearing loss prevention is listed among the 21 Priority Research Areas, as described in National Institute for Occupational Safety and Health (NIOSH)’s National Occupational Research Agenda.[1]
At a -5 dB signal-to-noise ratio, poor speech intelligibility results were obtained for all earmuff test conditions
Average speech intelligibility scores ranged from 46% to 72% at a 0 dB signal-to-noise ratio
Summary
Hearing loss prevention is listed among the 21 Priority Research Areas, as described in NIOSH’s National Occupational Research Agenda.[1]. Efforts to prevent occupational hearing loss appear to be hindered because the problem is insidious and occurs without causing pain in affected individuals. One consequence of noise-induced hearing loss is a reduced quality of life due to the inability to communicate with family, friends, and the general public. This normally occurs after the hearing loss has progressed significantly and the damage is irreversible. This problem can have other serious repercussions, considering that a study of older workers with disabilities indicated hearing loss as a risk factor for occupational injury.[2]
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