U.S. Navy Flight Deck Hearing Protection use Trends: Survey Results


ABSTRACT Hearing loss claims have risen steadily in the U.S. Department of Veterans Affairs across all military services decades. The U. S. Navy, with U.S. Air Force and industry partners, is working to improve hearing protection and speech intelligibility for aircraft carrier flight deck crews who work up to 16 hr per day in 130-150 dBA tactical jet aircraft noise. Currently, flight deck crews are required to wear double hearing protection: earplugs and earmuffs (in a cranial helmet). Previous studies indicated this double hearing protection provides approximately 30 dB of noise attenuation when earplugs are inserted correctly and the cranial/earmuffs are well-fit and in good condition. To assess hearing protection practices and estimate noise attenuation levels for active duty flight deck crews, Naval Air Systems Command surveyed 301 U.S. Navy Atlantic and Pacific Fleet flight deck personnel from four aircraft carriers and two amphibious assault ships. The survey included a detailed assessment of cranial helmet fit and maintenance condition; earplug use and insertion depth; anthropometric head size measures; and personal/historical data. This survey identified numerous technological and hearing conservation policy changes to improve hearing protection for flight deck crews. Based on these findings, the U.S. Navy is improving procedural documentation for flight deck hearing protection fit, use, and maintenance as well as developing and fielding enhanced hearing protection technology in joint efforts with the U.S. Air Force.

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    ABSTRACT: Noise-induced hearing loss (NIHL) is costly in both human and economic terms. One means of reducing NIHL is to apply engineering controls to hazardous noise sources. To trade off the cost of engineering controls against the total direct monetary costs incurred by NIHL, a means of predicting the amount of NIHL that will be incurred over the life-cycle of a hazardous noise source is necessary. A widely known algorithm for the prediction of NIHL is published in ANSI S3.44-1996. However, the algorithm inputs, noise exposure level and duration, may be difficult to determine in some cases. This paper describes the conceptual basis of an approach for using ANSI S3.44-1996 to predict hearing thresholds in a population even when noise exposure levels and durations are not precisely known, and demonstrates the initial application of this approach to a single military population. Retrospective data were obtained on the hearing-threshold levels, demographic characteristics, and noise exposure history of 250 male U.S. Navy machinists' mates. A maximum-likelihood fitting procedure was developed in which the noise level input to the algorithm was varied in order to determine the noise level that best accounted for all of the data. The maximum likelihood fitting produced a value for the noise level input of approximately 93 dBA, with a standard error of approximately 0.3. The low standard error virtually eliminates any estimate above 94 or below 92 dBA, and indicates that a good fit to the data was achieved. This research demonstrates the feasibility of calibrating the algorithm to an individual population, even when noise exposure level or duration is not precisely known. Future work will focus on validating and generalizing this approach so that it may be used to predict hearing-threshold levels in various populations. Such an approach may be used in calculating potential cost savings in compensable hearing loss due to the application of noise control solutions.
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    ABSTRACT: Hearing loss has long been associated with the operation of aircraft. Some of the first hearing protectors were developed for use around military aircraft. Today's high performance military aircraft generate noises which typically range from 110 dB to 150 dB. Normally, the source of the noise cannot be quieted without loss in performance. Therefore hearing protection is the primary tool to mitigate aviation personnel noise exposures during operations of aircraft. This paper describes a joint U.S. Air Force and U.S. Navy approach to improve hearing protection and reduce hearing loss risk. The approach included research and development to improve hearing protection as well as technologies to allow personnel to be moved from high noise work areas; recommendations for administrative controls; and investigation of hearing protective pharmaceuticals. The development of improved passive and active hearing protection technologies employed a three phased approach with attenuation performance goals for near-term (35-40 dB), mid-term (40-45 dB), and long-term (45-50+ dB) solutions. The technologies which have been developed to achieve the first two hearing protection goals will be described along with their attenuation performance characteristics. Ongoing research to achieve the long term (45-50+ dB) goal will be described with considerations of bone conducted noise pathways.
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    ABSTRACT: In a longitudinal study with 338 volunteers, audiometric thresholds and otoacoustic emissions were measured before and after 6 months of noise exposure on an aircraft carrier. While the average amplitudes of the otoacoustic emissions decreased significantly, the average audiometric thresholds did not change. Furthermore, there were no significant correlations between changes in audiometric thresholds and changes in otoacoustic emissions. Changes in transient-evoked otoacoustic emissions and distortion-product otoacoustic emissions were moderately correlated. Eighteen ears acquired permanent audiometric threshold shifts. Only one-third of those ears showed significant otoacoustic emission shifts that mirrored their permanent threshold shifts. A Bayesian analysis indicated that permanent threshold shift status following a deployment was predicted by baseline low-level or absent otoacoustic emissions. The best predictor was transient-evoked otoacoustic emission amplitude in the 4-kHz half-octave frequency band, with risk increasing more than sixfold from approximately 3% to 20% as the emission amplitude decreased. It is possible that the otoacoustic emissions indicated noise-induced changes in the inner ear, undetected by audiometric tests. Otoacoustic emissions may therefore be a diagnostic predictor for noise-induced-hearing-loss risk.
    The Journal of the Acoustical Society of America 08/2006; 120(1):280-96. DOI:10.1121/1.2204437 · 1.56 Impact Factor


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