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Research Goal 1

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Research Goal 4

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R&D Portfolio - Research Goal 4.3:
Prevent hearing loss from impulsive noise through development of standards and instrumentation

Over 1.8 million U.S. workers are exposed to potentially hazardous levels of impulsive noise. This estimate includes federal, state, and local law enforcement officers, DOD infantry, armor and artillery personnel, and workers in the construction trades.[21],[22],[23] It is also estimated that 50% of U.S. industrial workers shoot firearms as part of recreational target practice or hunting.[24]

High-intensity impulsive sounds have been shown to be more damaging to hearing than continuous sounds.[25] Exposure to impulsive sound can cause acute acoustical trauma, which can be followed by symptoms such as tinnitus and temporary hearing impairment. Sudden hearing loss may also occur from exposure to impulsive sounds that exceed a critical sound pressure level by causing direct mechanical damage to the inner ear.

In 2001, HLR program engineers and scientists identified limitations of existing sound instruments and measurement standards. Available regulations and standards do not provide guidance on how to evaluate impulsive sounds that exceed a peak C-weighted sound level of 140  dB. Since no standard method exists to characterize exposure to impulsive sounds, hearing professionals as well as occupational safety and health professionals in the U.S. continue to rely on outdated and incomplete national standards to assess the hazard of exposure to impulsive sounds.

The HLR program started examining workplace impulsive noise and its effects on the auditory system in the 1980s.[26],[27] In the late 1980s, researchers conducted animal studies to examine the effect of continuous versus impulse noise on the hearing of chinchillas.[28] Beginning in 2001, the HLR program conducted a series of HHEs to examine exposure of law enforcement officers to impulsive noise during weapon qualification exercises. NIOSH engineers and scientists identified limitations of existing sound instruments and measurement standards. Current research is focused on developing new technology as well as standards for measuring and evaluating exposure to impulsive sounds, and leading national efforts to develop an occupational damage risk criterion for impulse noise exposure.[29], [30], [31], [32], [33], [34], [35], [36]

The HLR program funded and cooperated on studies on impulsive noise through its extramural research program. The extramural program supported studies at the:

·    Auditory Research Laboratory, State University of New York, Plattsburgh

·    Callier Center for Communication Disorders, University of Texas, Dallas

·    Hearing Research Laboratory, Department of Communicative Disorders and Sciences, State University of New York, Buffalo.

The studies found that high-intensity impulsive sounds can cause hearing loss via two mechanisms in the auditory system: necrosis resulting from compromised membranes of the sensitive structures of the inner ear and through apoptotic processes leading to programmed cell-death.

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[21]“Law Enforcement Statistics.” [2000] [Online] Available at

Bureau of Justice Statistics. U.S. Department of Justice, Washington, D.C.

[22]U.S Department of Defense. [1997]. MIL-STD-1474D. Design Criteria Standard, Noise Limits, Washington, D.C.

[23]“Occupational Employment Statistics”. [2001]. [Online] Available at

Bureau of Labor Statistics. U.S. Department of Labor, Washington, D.C.

[24]Clark, W.W. [1991]. “Noise exposure from leisure activities: A review.” J. Acoust. Soc. Am. 90, 175–181.

[25]Henderson, D., Hamernik, R.P. [1986]. “Impulse noise: Critical review” J. Acoust. Soc. Am. 80 (2):569-584.

[26] Erdreich J [1984]. Characterization and measurements of work site impulse noise. Noise Control Engineering Journal 23 (3) 120-126.

[27] Erdreich J [1986]. A distribution based definition of impulse noise. Journal of Acoustical Society of America 79 (4) 990-998.

[28] Dunn DE, Davis RR, Merry CJ, Franks JR [1991]. Hearing loss in the chinchilla from impact and continuous noise exposure. Journal of the Acoustical Society of America 90 (1) 1979-1985.

[29] Kardous, CA [2005]. International Bureau of World Intellectual Property Organization – International Patent Application Number PCT/U.S.2004/022499. System for Monitoring Exposure to Impulsive Noise.

[30] Kardous CA [2004]. Noise Dosimeters. Book Chapter 36, to be published in Malcolm Crocker Handbook of Noise and Vibration Control. John Wiley & Sons, New York.

[31] Kardous CA [2003]. U.S. Patent and Trademark Office System for Monitoring Exposure to Impulsive Noise. U.S. Provisional Patent Application Number 60/487,449.

[32] Kardous CA [2003]. New design concept for an impulse noise dosimeter. American Industrial Hygiene Conference, May 2003, Dallas, Texas.

[33] Kardous CA, Murphy WJ, Willson RD [2003]. New design concept for an impulse noise dosimeter. National Hearing Conservation Association- Best Practices Workshop, May 2003, Cincinnati, Ohio.

[34] Kardous CA, Murphy WJ, Willson RD, [2003]. Personal noise exposure assessment from small firearms. Acoustical Society of America Conference, April, 2003, Nashville, Tennessee.

[35] Kardous CA, Willson RD [2003]. Limitations of using dosimeter in impulse noise environments, Journal of Occupational and Environmental Hygiene, 1 (7) pp.456-462.

[36] Kardous CA, Willson RD, Hayden CS [2003] – Noise assessment and abatement strategies an indoor firing range. Applied Occupational and Environmental Hygiene [18] (8) pp. 629-636.


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