Biomedical subjects

C A Champlin

Publications and source records attributed to C A Champlin.

21 records · Page 2Linked to original sources

PubMed1989

Behavior of spontaneous otoacoustic emissions following intense ipsilateral acoustic stimulation.

Following presentation of brief, intense pure tones spontaneous otoacoustic emissions (SOAEs) were reduced in frequency and/or amplitude. The effects were highly tuned with exposures between 1/8 and 5/8 of an octave below the SOAE producing the maximum changes. Exposure frequencies above the SOAE had no effect. The degree of tuning observed depended upon the post-exposure time sampled, with sharpness maximal between 3 and 120 s post-exposure. The effects increased nonlinearly as exposure level and duration were increased. The recovery functions were biphasic, the first phase being rapid and non-monotonic over about 2 min, while the second phase was monotonic and slow, sometimes taking several hours. These data are consistent with changes in outer hair cell (OHC) function and support the hypothesis that OHC changes underlie behavioral temporary threshold shift (TTS).

Acoustic Stimulation↗

PubMed1989

Reductions in overshoot following intense sound exposures.

Overshoot refers to the poorer detectability of brief signals presented soon after the onset of a masking noise compared to those presented after longer delays. In the present experiment, brief tonal signals were presented 2 or 190 ms following the onset of a broadband masker that was 200 ms in duration. These two conditions of signal delay were tested before and after a series of exposures to a tone intense enough to induce temporary threshold shift (TTS). The magnitude of the overshoot was reduced after the exposure when a TTS of at least 10 dB was induced, but not when smaller amounts of TTS were induced. The reduction in overshoot was due to a decrease in the masked thresholds with the 2-ms delay; masked thresholds with the 190-ms delay were not different pre- and post-exposure. The implication is that the mechanisms responsible for the normal overshoot effect are temporarily inactivated by the same stimulus manipulations that produce a mild exposure-induced hearing loss. Thus the result is the paradox that exposure to intense sounds can produce a loss of signal detectability in certain stimulus conditions and a simultaneous improvement in detectability in other stimulus conditions.

Acoustic Stimulation↗

PubMed1988

Effects of intense pure tones on auditory temporal acuity.

Gap detection thresholds (GDTs) were obtained from human listeners before and after exposure to a brief 0.4- or 1.7-kHz tone. The temporary threshold shift (TTS) produced 2 min after an exposure was approximately 10 dB. GDT stimuli were octave-band noises centered at one of three frequencies: the exposure frequency, one-half octave above the exposure frequency or one octave above the exposure frequency. GDTs were obtained at 35, 55, and 75 dB SPL at each center frequency. GDT and TTS recovery were monitored at logarithmically-spaced time intervals after the exposures. Following the 1.7-kHz exposure, shifts in post-exposure GDT were only obtained with the low-level stimulus conditions--the magnitude of GDT shift was correlated with the size of the TTS, and the shifts in GDT and absolute threshold required similar amounts of time to recover. Significant post-exposure shifts in GDT were also observed following the 0.4-kHz exposure. However, shifts were found at frequencies where there was no measurable TTS, and they required longer periods of time to recover than did absolute threshold.

Auditory Fatigue↗