HEARING PROTECTION WITH INTEGRATED IN-EAR DOSIMETRY: A NOISE DOSE STUDY

摘要

Military personnel working in high noise environments can bernexposed to continuous noise levels up to 150 dB. United Statesrn(US) Department of Defense (DoD) Hearing ConservationrnPrograms (HCPs) set safe noise exposure limits to reducernthe risk for noise induced hearing loss. These daily noisernexposure limits were based on ambient noise levels and thernduration of time spent in that noise environment. Currentrndosimeters, worn on the lapel of personnel and at least onernsystem worn under a hearing protector, were designed tornmeasure noise levels and calculate noise dose, but do notrnprovide a validated measure of noise dose external to or under arnhearing protector. Noise dose under hearing protectors can bernestimated by subtracting the real ear attenuation (REAT) data,rncollected in accordance with the American National StandardsrnInstitute (ANSI) S12.6, at each octave band from thernambient octave band noise. This procedure gives accuraternresults for group data, but does not account for individualrnvariations in effective attenuation. To address this issue, the USrnNaval Air Systems Command (NAVAIR) led the developmentrnof ship suitable in-ear dosimetry integrated into a hearingrnprotector, and co-sponsored an effort executed by the Air ForcernResearch Laboratory (AFRL) to calibrate in-ear noise dosernreadings. This was accomplished by conducting human noisernexposure experiments, with and without hearing protection,rnwhich calculated noise dose from temporary threshold shiftsrn(TTS) in hearing. Ten subjects participated in the study. Noisernlevels were 91, 94, and 97 dB for up to 2 hrs, 1 hr, andrn30 minutes respectively. These exposure levels were wellrnwithin US DoD safe noise exposure guidelines (DoD HCP). Data will be presented describing the open and occludedrn(protected) ear TTS response to noise dose achieved by subjectsrnin the experiment. Preliminary findings indicate that humanrnsubject data is extremely important in developing andrnvalidating calibration factors for any type of noise dosimeterrnbut is especially important for in-ear dosimetry. Results fromrnthis study demonstrated that the REAT noise dose estimationsrnand the in-ear dosimetry earplugs consistently overestimatedrnthe effective noise dose received by subjects. However, morernthan 10 subjects are required to improve the confidence level ofrnthe estimated calibration factor.