Asymptotic threshold shift in chinchillas exposed to impulse noise.
Blakeslee-EA; Hynson-K; Hamernik-RP; Henderson-D
Department of Otolaryngology and Communication Sciences, State University of New York, Upstate Medical Center, Syracuse, New York, 1981 Jan; :1-31
In an effort to more fully understand the results of long term exposures to impulse noise as they relate to asymptotic threshold shift (ATS), five monaural chinchillas were exposed to a repetitive, reverberant impulse noise for 10 days. The noise was generated by a mechanized hammer hitting a steel plate at the rate of one beat per second. The average peak over pressure within the holding cage was 113 decibels (dB) sound pressure level. Auditory thresholds were measured before exposure. Similar measurements were taken at 0.5, 1, 1.4, 2, 2.8, 4, 8, and 16 kilohertz (kHz) using shock avoidance conditioning. Thresholds were monitored on a daily basis during exposure at 0.5 and 8kHz. Threshold shift at 8kHz had reached an asymptotic level within 1 hour from the start of the exposure while threshold shift at 0.5kHz leveled off after 24 hours of exposure. ATS levels for both frequencies varied between 30 to 50dB across animals. By 40 days after exposure the median threshold shift for both frequencies recovered to within 10dB of normal. Maximum permanent threshold shift was at 2 and 2.8kHz with median PTS of 17 and 13dB, respectively. The cochleas were examined histologically. The stability of the ATS produced by impulse noise and the consistency across the five animals suggest that the phenomenon may be useful in the systematic study of both temporary threshold shift and noise induced permanent threshold shift.
NIOSH-Grant; Noise-induced-hearing-loss; Noise-exposure; Laboratory-animals; Hearing-threshold; Sensory-thresholds
Otolaryngology Upstate Medical Center Departm 750 E Adams Street Syracuse, N Y 13210
Final Grant Report
NTIS Accession No.
Department of Otolaryngology and Communication Sciences, State University of New York, Upstate Medical Center, Syracuse, New York
Upstate Medical Center, Syracuse, New York