Distortion-product emissions in rabbit: II. Prediction of chronic-noise effects by brief pure-tone exposures.
In an attempt to predict the susceptibility of the cochlea to the harmful influences of excessive sound, the effects of initially exposing the same rabbits to brief pure-tones were related to the subsequent effects of octave-band noise (OBN) exposure using measures of distortion-product otoacoustic emissions (DPOAEs). The pure-tone exposure paradigm consisted of determining the rate at which a 100-dB SPL, low-frequency tone reduced the amplitude of a 1.5-kHz DPOAE, elicited by 50-dB SPL primaries. To establish the stability of the rate-reduction index, the tonal-exposure protocol was repeated on three separate occasions for each subject. Subsequently, the same rabbits were exposed chronically to a 95-dB SPL OBN, centered at 1-kHz, until DPOAE amplitudes between 1-5 kHz were diminished to noise-floor levels, i.e., by 10-30 dB, in response to 45-dB SPL primaries. The results revealed a visually apparent relation between the slope of the tonal-induced DPOAE-loss functions and the number of days required to reach the criterion decrement in emission level during chronic exposure to noise. Analysis of the frequency extent of the noise-induced changes revealed significant correlations between the previously measured rate of pure-tone induced reductions of DPOAE amplitude and the subsequent amount of decrement produced by OBN exposure. Thus, rabbits exhibiting slow rates of tonal-induced decrements in low-frequency DPOAEs were resistant to the amplitude-reducing effects of a subsequent chronic OBN exposure in that it typically took more than four days to achieve the targeted amount of DPOAE loss.(ABSTRACT TRUNCATED AT 250 WORDS)
Mensh
B D
BD
Division of Neuroscience, Baylor College of Medicine, Houston, Texas.
Lonsbury-Martin
B L
BL
Martin
G K
GK
D000161:Acoustic Stimulation; D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D006317:Hearing Loss, Noise-Induced / Q000209:etiology* / Q000503:physiopathology; D006801:Humans; D009622:Noise / Q000009:adverse effects*; D017084:Otoacoustic Emissions, Spontaneous / Q000502:physiology*; D011817:Rabbits; D013045:Species Specificity; D013997:Time Factors