Reflex Threshold Shift in Chinchillas Following a Prolonged Exposure to Noise The acoustic reflex is considered to reduce transmission across the middle ear and thereby protect the inner ear from intense sounds. The dynamic properties of this reflex seem to be a function of the duration of the eliciting stimulus. Assessment of the protective action afforded by middle-ear muscle contractions for ... Research Article
Research Article  |   March 01, 1979
Reflex Threshold Shift in Chinchillas Following a Prolonged Exposure to Noise
 
Author Affiliations & Notes
  • Kenneth J. Gerhardt
    Kent State University, Kent, Ohio
  • William Melnick
    Ohio State University, Columbus
  • John A. Ferraro
    Ohio State University, Columbus
Article Information
Research Articles
Research Article   |   March 01, 1979
Reflex Threshold Shift in Chinchillas Following a Prolonged Exposure to Noise
Journal of Speech, Language, and Hearing Research, March 1979, Vol. 22, 63-72. doi:10.1044/jshr.2201.63
History: Received February 6, 1978 , Accepted July 12, 1978
 
Journal of Speech, Language, and Hearing Research, March 1979, Vol. 22, 63-72. doi:10.1044/jshr.2201.63
History: Received February 6, 1978; Accepted July 12, 1978

The acoustic reflex is considered to reduce transmission across the middle ear and thereby protect the inner ear from intense sounds. The dynamic properties of this reflex seem to be a function of the duration of the eliciting stimulus. Assessment of the protective action afforded by middle-ear muscle contractions for long-term noise exposures requires the knowledge of how these dynamic properties change under such conditions. Round window electrodes were implanted in eight chinchillas. Changes in the threshold of the acoustic reflex were measured during an eight-hour exposure at 95 dB SPL to an octave-band noise centered at 0.5 kHz. The criterion measure of the acoustic reflex was a change in the amplitude of the cochlear microphonic generated by a 0.5 kHz eliciting tone. Thresholds of the acoustic reflex increased systematically throughout the noise exposure up to approximately 14 dB after 8 hours. The time course of the changes in the threshold of the acoustic reflex was nearly identical to the time course of behaviorally measured changes in the auditory sensitivity as reported by Carder and Miller (1972).

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