The interaction between continuous and impluse noise: frequency effects.
Hamernik-RP; Ahroon-WA; Henderson-D; Salvi-RJ
Recent advances in researches on the combined effects of environmental factors. Okada A, Manninen O, eds. Kanazawa, Japan: KYOEI Comoany. Ltd., 1987 Jan; :1-20
This paper reviews several animal experiments which illustrate how the energy frequency spectrum of an impulse noise influences the hearing loss resulting from a combination of impulse and continuous noise. Chinchillas were used as the experimental animal. Seven experimental groups each containing 5 animals were exposed to one of the following noise conditions. (1) a 2.0-4 kHz band of noise at 95 dB SPL for one hour. 92) Impulse noise generated by an electrical spark discharge. The duration of the first positive overpressure of the Friedlander wave thus generated was varied in three steps from approximately 32 micro sec. to 64 micro sec. at a peak SPL of 158 dB. The different wave durations caused the energy peak of the impulse to shift from approximately 8n kHz down to 4 kHz. The impulses were presented at the rate of 1/min for 50 min. (3) The third series of exposures consisted of combinations of the above two sets of exposures. This experimental design allowed us to study the effect of a shifting impulse spectrum on the hearing loss acquired from very brief duration blast waves. The results show that a synergistic interaction is most likely to occur when there is a spectral overlap of energy between the impulse and the continuous noise. The effects of the above exposures on hearing were measured using the evoked auditory potentials on each animal before and after exposure. The status of the cochlear sensory epithelia was evaluated using surface preparation histology.
Animals; Laboratory-animals; Impulse-noise; Noise-frequencies; Noise-exposure; Noise-induced-hearing-loss; Hearing-loss; Hearing; Exposure-levels; Risk-factors; Auditory-system;
Author Keywords: evoked response; hair cells; impulse noise; interactions
Recent advances in researches on the combined effects of environmental factors
State University of New York at Buffalo, Buffalo, New York