The Acoustic Reflex and Temporary Threshold Shift: Temporal Characteristics

1977 ◽  
Vol 20 (3) ◽  
pp. 565-573 ◽  
Author(s):  
R. S. Karlovich ◽  
H. A. Osier ◽  
H. N. Gutnick ◽  
R. G. Ivey ◽  
K. Wolf ◽  
...  
Keyword(s):  
Threshold Shift ◽  
Temporary Threshold Shift ◽  
Acoustic Reflex ◽  
Temporal Characteristics

Acoustic-Reflex Dynamics for Pulsed Signals

1978 ◽  
Vol 21 (2) ◽  
pp. 295-308
Author(s):  
Terry L. Wiley ◽  
Raymond S. Karlovich
Keyword(s):  
Duty Cycle ◽  
Acoustic Impedance ◽  
Normal Hearing ◽  
Broadband Noise ◽  
Threshold Shift ◽  
Temporary Threshold Shift ◽  
Acoustic Reflex ◽  
Stapedius Muscle ◽  
Duty Cycles

Contralateral acoustic-reflex measurements were taken for 10 normal-hearing subjects using a pulsed broadband noise as the reflex-activating signal. Acoustic impedance was measured at selected times during the on (response maximum) and off (response minimum) portions of the pulsed activator over a 2-min interval as a function of activator period and duty cycle. Major findings were that response maxima increased as a function of time for longer duty cycles and that response minima increased as a function of time for all duty cycles. It is hypothesized that these findings are attributable to the recovery characteristics of the stapedius muscle. An explanation of portions of the results from previous temporary threshold shift experiments on the basis of acoustic-reflex dynamics is proposed.

Spectral and Temporal Parameters of Contralateral Signals Altering Temporary Threshold Shift

1974 ◽  
Vol 17 (1) ◽  
pp. 41-50 ◽  
Author(s):  
Raymond S. Karlovich ◽  
Terry L. Wiley
Keyword(s):  
Dynamic Properties ◽  
Broad Band ◽  
Normal Hearing ◽  
Threshold Shift ◽  
Temporary Threshold Shift ◽  
Acoustic Reflex ◽  
Contralateral Stimulation ◽  
Band Noise ◽  
Resultant Data ◽  
Contralateral Ear

The test ear of each of nine normal-hearing subjects was exposed for three minutes to a 1000-Hz tone at 110 dB SPL. Either a 4000-Hz tone at 105 dB SPL or a broad-band noise at 100 dB SPL was presented to the contralateral ear during exposure. Four different temporal patterns were used for each contralateral signal: (1) continuous, (2) 18 seconds on/18 seconds off, (3) 1.8 seconds on/1.8 seconds off, and (4) 0.18 seconds on/0.18 seconds off. A control condition, consisting of the absence of contralateral stimulation, also was used. Pre- and postexposure thresholds for the test ear were tracked at a signal one-half octave above the exposure frequency. Resultant data indicated that reduction in temporary threshold shift was greatest for conditions involving rapidly pulsed (1.8 and 0.18 seconds on-off) contralateral signals. We hypothesized that these data were reflective of the dynamic properties of the acoustic reflex. Specifically, we posited that the acoustic reflex manifests less adaptation in response to rapid signal-repetition rates and relatively more adaptation to sustained or slowly pulsed signals.

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