Impulsive noise: A brief review

Short duration impulsive noise is typically generated by a release of pressure (impulse) or a collision of solid objects (impact). In animal models these noises have been shown to be more damaging to the ear than continuous noise of equal energy (Hamernik and Henderson, 1974; Dunn et al., 1991; Hamernik et al., 1994). Impulsive noises are common in manufacturing, construction, public safety and the military. All police and sheriff officers must qualify annually on firearms which generate impulsive noise. The US Veterans Administration's major compensation costs are for former military members noise-induced hearing loss and tinnitus. The US National Institute for Occupational Safety and Health (NIOSH) (p. xiv, 1998) defines impulsive noise as a noise with sharp rise and rapid decay, 1 s or less in duration. Most researchers would consider a noise impulsive if it is a single pressure peak typically lasting milliseconds to microseconds without regard to intra-impulse interval (e.g. Fig. 1). The US Occupational Safety and Health Administration (OSHA) considers impulsive noises to be continuous if the intra-pulse interval as less than 1 s. OSHA also requires that all continuous and impulsive noises between 80 and 130 dB to be incorporated into the worker's daily dose. The use of standard industrial hygiene noise dosimeters to measure impulsive noises is inappropriate (Kardous and Willson, 2004). Dosimeter electronics “clip” at high input levels (greater than 130 dB) and do not have a fast enough time constant to capture impulses. Many sound level meters may be able to capture peak levels with a peak hold circuit depending upon the microphone and amplifier (e.g. Brüel & Kjær 2608 Measuring Amplifier). For about the past 10 years NIOSH has been developing a portable measurement system to measure firearm discharges and other