Auditory localization in the horizontal plane with single and double hearing protection

Introduction: Although single hearing protection devices such as earplugs or earmuffs are known to degrade sound localization, little is known about localization accuracy in double-hearing-protection conditions where both earplugs and earmuffs are worn at the same time. Methods: Listeners wearing earplugs, earmuffs, or a combination of earplugs and earmuffs were asked to localize short (250 ms) or long (continuous) pink noise signals originating from one of 24 loudspeaker locations in the horizontal plane. Results: When single hearing protection was worn, localization was reasonably accurate in the left-right dimension even when the stimuli were short in duration. When double hearing protection was worn, however, left-right localization accuracy was poor even when the stimuli were on continuously. A second experiment showed that localization accuracy with double hearing protection varied substantially across different listeners, but that it varied only slightly across refittings of the same earplugs and earmuffs on the same listener. A third experiment showed that double hearing protection impaired localization in the left-right dimension much more for narrowband sounds at frequencies above 500 Hz than it did for narrowband sounds at frequencies at or below 250 Hz. Discussion: The severe disruptions in performance that occurred when earmuffs and earplugs were worn simultaneously suggest the influence of a mechanism such as bone conduction that does not normally interfere with localization when only a single hearing protection device is used.