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Differences of CT (2f1 - f2) phase in psychophysical and physiological experiments
Hearing Research
|June 1, 1980
Summary
Psychophysical and neural studies reveal discrepancies in combination tone (CT) phase measurements. This suggests a real difference in intracochlear nonlinearity between humans and animals, necessitating new cochlear models.
Area of Science:
- Auditory Neuroscience
- Psychoacoustics
- Biophysics
Background:
- Combination tones (CTs) provide evidence for intracochlear distortion products.
- A significant discrepancy exists between psychophysical and neural CT phase measurements regarding stimulus amplitude dependence.
Purpose of the Study:
- Investigate if psychophysical cancellation tone phase accurately reflects intracochlear CT phase.
- Examine amplitude-dependent biases in CT phase measurements.
- Compare human and animal intracochlear nonlinearities.
Main Methods:
- Monaural cancellation and binaural lateralization psychophysical studies of CT interactions.
- Analysis of neural phase locking and cancellation of phase locking.
- Modification of Hall's nonlinear transmission line model.
Main Results:
- Psychophysical CT phase shows amplitude dependence, while neural phase does not.
- Binaural lateralization confirmed the amplitude dependence observed in monaural cancellation.
- Amplitude-dependent biases in cancellation measurements were too small to explain the observed phase differences.
Conclusions:
- A genuine difference in intracochlear nonlinearity exists between alert humans and anesthetized animals.
- The findings necessitate revised models of human cochlear nonlinearities, incorporating nonlinear stiffness.