Noisy equipment and processes are found throughout military operations, exposing service members to risks of hearing damage due to hazardous noise levels. This article provides an overview of the military noise environment for the non-expert and provides a general characterization of the noise by source type and operational category. The focus of the article is primarily related to the Army, but the same, or similar, equipment is used by the Navy, Marine Corps, and Air Force. Damage risk criteria used by the Army Public Health Command are discussed. In addition, the important role of hearing protection to mitigate the hazards of noise exposure is provided.
Noise, hearing loss, and electronic signal distortion, which are common problems in military environments, can impair speech intelligibility and thereby jeopardize mission success. The current study investigated the impact that impaired communication has on operational performance in a command and control environment by parametrically degrading speech intelligibility in a simulated shipborne Combat Information Center. Experienced U.S. Navy personnel served as the study participants and were required to monitor information from multiple sources and respond appropriately to communications initiated by investigators playing the roles of other personnel involved in a realistic Naval scenario. In each block of the scenario, an adaptive intelligibility modification system employing automatic gain control was used to adjust the signal-to-noise ratio to achieve one of four speech intelligibility levels on a Modified Rhyme Test: No Loss, 80%, 60%, or 40%. Objective and subjective measures of operational performance suggested that performance systematically degraded with decreasing speech intelligibility, with the largest drop occurring between 80% and 60%. These results confirm the importance of noise reduction, good communication design, and effective hearing conservation programs to maximize the operational effectiveness of military personnel.
There has been renewed interest in the human effects of excessive intermittent airborne noise occurring on the 03 Level (Gallery Deck) and on the Flight Deck during aircraft launch and recovery operations (“Flight Ops”) aboard U.S. Navy aircraft carriers. High noise levels cause crew fatigue, lost work hours, high crew turnover, safety problems, and worst case, hearing damage or loss of life. The cost of this problem can be quantified as part of the Total Ownership Cost of the ship by taking into account such factors as the cost of veterans' hearing compensation, crew retention bonuses, and crew turnover.
This interest has lead to at‐sea measurements of intermittent noise levels during flight operations on two operational aircraft carriers. This data provides the first detailed, systematic quantification of sound pressure levels, noise frequency content, noise time duration and frequency of events. The classic acoustic source/path/receiver approach was used to investigate noise sources and paths associated with the transmission of aircraft and machinery noise.
Solutions take a total ship engineering approach, combining Total Ownership Cost, Human Engineering, and industrial partnerships to develop cost effective solutions to mitigate noise associated with flight operations.
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