Correlations among evoked potential thresholds, distortion product otoacoustic emissions and hair cell loss following various noise exposures in the chinchilla.
Hear Res 2000 Dec; 150(1-2):245-257
Changes in cubic distortion product otoacoustic emissions (DeltaDPOAEs), evoked potential threshold shifts (TSs) and outer hair cell (OHC) losses were measured in a population of 95 noise-exposed chinchillas. Each animal was exposed to one of 23 different noises in an asymptotic threshold shift (ATS) producing paradigm or an interrupted noise paradigm which typically produced a toughening effect. Noises were narrow band (400 Hz) impacts with center frequencies of 0.5, 1.0, 2.0, 4.0 or 8.0 kHz presented 1 impact/s at peak SPLs of 109, 115, 121 or 127 dB. The duration of the exposures was 24 h/day for 5 days (ATS paradigm) or 6 h/day for 20 days (toughening paradigm). Based on a linear regression analysis of individual subject and group mean data, correlations among the following dependent variables were made: DeltaDPOAEs, ATS, toughening or TS recovery (TS(r)), permanent threshold shift (PTS) and OHC loss. Correlations among these metrics were generally highest for DPOAE primary frequency levels, L(1)=L(2)=70 dB. Correlation between DeltaDPOAE and TS(r) was typically low, while a considerably higher correlation was found between DeltaDPOAE and ATS. Correlations among the permanent measures of noise-induced effects, i.e. for DeltaDPOAE/PTS and DeltaDPOAE/OHC loss were typically poor when there was only a small or a moderate noise-induced effect (PTS<25 dB and DeltaDPOAE<20 dB). However, for PTS<25 dB the correlation between PTS and OHC loss was considerably better than the correlation between DeltaDPOAE and OHC loss. For more severe noise-induced changes there was generally a good correspondence between OHC loss, PTS and DeltaDPOAE metrics.
Noise-exposure; Animals; Animal-studies; Threshold-limit-values; Hearing-impairment; Hearing-conservation; Sensitivity-testing; Auditory-system; Hearing-threshold;
Author Keywords: Distortion product emission; Asymptotic threshold shift; Interrupted noise exposure; Sensory cell loss
Auditory Research Laboratory, Plattsburgh State University of New York, 107 Beaumont Hall, 101 Broad St., Plattsburgh, NY 12901-2681
State University of New York at Buffalo, Buffalo, New York