Noise control: a 100-year-old problem.
Noise is the most prevalent occupational health hazard health hazard Occupational safety Any agent or activity posing a potential hazard to health. Cf Physical hazard. , affecting millions of people in various work locations. It has been known at least 100 years that excessive noise exposure can result in permanent hearing loss. Noise-induced permanent threshold shifts affect 10 to 20 million people in the United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area. alone. Approximately 600 million people worldwide are exposed to occupationally hazardous noise levels. As an example, construction work commonly exceeds the noise levels that require use of hearing protection, thus creating a risk of permanent hearing loss in unprotected workers.
Relationship between noise exposures and hearing loss. A clear association has been established between unprotected noise exposure and the probability and severity of permanent hearing loss. Literally millions of industrial workers and thousands of test subjects around the world have demonstrated this relationship. Studies show a dose-response relationship between the noise exposure of unprotected populations and their rate and severity of permanent hearing loss.
Military noise exposures and associated hearing loss. The Department of Defense is among the world's largest industrial-maintenance operations. All the noisy operations common to shipyards, aviation depots, and vehicle and facility maintenance are performed by military, civilian and supporting contractor personnel. Additionally, operation of military vehicles Military vehicles include all land combat and transportation vehicles, excluding rail-based, which are designed for or are in significant use by military forces.
See also list of armoured fighting vehicles. , ships, aircraft, and other equipment creates a variety of noise exposures.
Weapons firing both during training and combat operations add significantly to potential personnel exposures. The short but intense "impulse" noise has different occupational exposure criteria from continuous "steady state" noise exposures common to operations of machinery or vehicles. Special care in using protective equipment is essential during exposures to weapons firing because of the potential for acute injury to eardrums and the potential for damage to the hearing mechanism in the inner ear, resulting in a permanent reduction on sensitivity to sound.
The range of exposures common to Navy and Marine Corps operations show that many exceed the level of sound attenuation Loss of signal power in a transmission.
The reduction in level of a transmitted quantity as a function of a parameter, usually distance. It is applied mainly to acoustic or electromagnetic waves and is expressed as the ratio of power densities. provided by currently available protective equipment.
Special issues in military settings. These factors create particularly intense exposures in military settings:
* The range of industrial maintenance and support operations.
* Weapons firing and explosives/ordnance use.
* Lack of consistent attention to noise controls in design requirements.
* Limited time for "quiet" periods (without exposure) for shipboard personnel, where long-duration work shifts and noisy berthing areas may limit the opportunity for recovery.
* Silence (or at least relative quiet) retains its military importance and has contributed to major technology investments that surface ships can use with limited additional cost or development.
Military and civilian populations exposed. Military personnel in deployed/operational settings, particularly in aviation, shipboard and combat support roles, are commonly exposed to high levels of noise. The overall rate of significant threshold shifts recorded for personnel in the hearing-conservation program via the DOEHRS-HC (Defense Occupational and Environmental Health Readiness System-Hearing Conservation) database is approximately 15 percent, although significantly higher rates of reported hearing loss may exist in specific occupations.
Veterans Administration (VA) compensation indicates extent of problem. Tinnitus Tinnitus Definition
Tinnitus is hearing ringing, buzzing, or other sounds without an external cause. Patients may experience tinnitus in one or both ears or in the head. (ringing in the ears) and hearing loss are the No. 1 and No. 2 diagnosed impairments for the VA. The combined bill associated with all services in 2006 was approaching $1.4 billion. Although the eligibility for hearing aids Hearing Aids Definition
A hearing aid is a device that can amplify sound waves in order to help a deaf or hard-of-hearing person hear sounds more clearly. is relatively lenient, the degree of functional disability linked to eligibility for compensation is significant. The threshold for 10 percent VA disability and a related limited compensation is a bilateral hearing loss of more than 56 dB--approximately the sound level of a normal conversation. Financial impact, though, doesn't reflect the human effect of hearing loss. A person who qualifies for this type of compensation, or the civilian equivalent, almost always is greatly impaired in their ability to communicate with those around them (especially in a crowd or presence of background noise), to enjoy the subtleties of music, or just to listen to the sounds of nature.
By Mark Geiger, M.S., CIH CIH Chartered Institute of Housing (UK)
CIH Certified Industrial Hygienist (ABIH)
CIH Constant Image Height
CIH Camshaft in Head (engine)
CIH Chen Ing-Hau , CSP (1) (Certified Systems Professional) An earlier award for successful completion of an ICCP examination in systems development. See ICCP.
(2) (Commerce Service P , OpNav Safety Liaison Office