Sound attenuation from earmuffs and earplugs in combination – Maximum benefits vs. missed information


  1. Abel, S.M.
  2. Odell, P.
Corporate Authors
Defence R&D Canada - Toronto, Toronto ONT (CAN)
Noise levels from military aircraft range from 100-130 dBA. Peak pressure levels from large caliber weapons may reach 180 dB SPL. To protect against hearing loss, individuals are encouraged to wear double hearing protection. The present study determined ways to maximize benefit. Hearing thresholds from 0.25-8 kHz and consonant discrimination were assessed in normal-hearing subjects with ears unoccluded and fitted with highly rated earmuffs and earplugs, singly or in combination. The earplugs were available in two sizes. Individual selection was based on best fit. Attenuation values were derived from the threshold measurements. With the muff, plug, and muff and plug in combination, thresholds ranged from 35-48 dB SPL, 40-55 dB SPL, and 44-66 dB SPL, respectively, across the frequencies tested. The combination (without regard to size of plug) resulted in attenuation values of 38-54 dB. With the smaller of the two plugs, low-frequency values as high as 53-61 dB were realized. Consonant discrimination decreased by 6-8% relative to unoccluded listening for the devices worn singly and by 22% with the devices in combination. These findings show that sufficient low-frequency attenuation may be achieved with muffs and plugs in combination to prevent hearing loss from operational noise. Attenuation may be maximized by choosing a smaller earplug to achieve a better fit. Possible downsides are reduced detection of warning sounds and speech intelligibility. To be heard these should surpas

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hearing conservation, low-frequency noise exposure, communication deficits
Report Number
DRDC-TORONTO-SL-2006-058 — Scientific Literature
Date of publication
15 Dec 2006
Number of Pages
Electronic Document(PDF)

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