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An Experimental Basis for the Estimation of Auditory System Hazard Following Exposure to Impulse Noise

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The energy spectrum of a noise is known to be an important effects of a traumatic exposure. However, existing criteria for exposure to impulse noise do not consider the frequency spectrum of an impulse as a variable in the evaluation of the hazards to the auditory system. This report presents the results of three studies that were designed to determine the relative potential that impulsive energy has in causing auditory system trauma. Four hundred and seventy five 475 chinchilla were used in these experiments. Pre- and post- exposure hearing thresholds were measured on each subject. In the first study, the noise exposure stimuli consisted of six different computer-generated narrow band tone bursts having center frequencies located at 0.260, 0.775, 1.025, 1. 350, 2.450, and 3.550 kHz. Each narrow band exposure stimulus was presented at two to four different intensities. An analysis of the audiometric data allowed a frequency weighting function to be derived. This weighting function de- emphasizes low frequency energy more than the conventional A-weighting function. In the second study, the exposures consisted of two--types of broad band computer synthesized impulses. Subjects were exposed to 100 impulses at a rate of 1-per-3-seconds. Each type of impulse was presented at 3 intensities. The third study used impulses generated by three different diameter shock tubes. Subjects were exposed to 1, 10, or 100 impulses at one of three intensities. The results of the second and third studies were interpreted using the weighting function derived from the first study. The hearing loss from all three studies is a linear function of the weighted SEL calculated using the weighting function, derived in the first study. Impulse noise, Hearing, Chinchilla, Audiometry and histology.

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  • Anatomy and Physiology
  • Radiofrequency Wave Propagation

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