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Stimulated acoustic emissions from within the human auditory system
The Journal of the Acoustical Society of America
|November 1, 1978
Summary
A novel auditory phenomenon was discovered in the human ear's acoustic response. This slow decay component, originating in the cochlea, is absent in deafened ears, suggesting a nonlinear cochlear mechanism.
Area of Science:
- Auditory Neuroscience
- Human Physiology
Background:
- The acoustic impulse response of the human ear is crucial for understanding auditory processing.
- Previous research has focused on early response components, neglecting later stages.
Purpose of the Study:
- To investigate a new auditory phenomenon in the late acoustic impulse response (AIR) of the human ear.
- To characterize the waveform and decay properties of the AIR beyond 5 ms post-excitation.
Main Methods:
- Signal averaging techniques were employed to analyze the AIR.
- The study focused on responses to acoustic impulses near the threshold of audibility.
- Waveform analysis extended to post-excitation times exceeding 5 ms.
Main Results:
- A slow-decaying response component was identified beyond 5 ms, distinct from middle ear contributions.
- The oscillatory response decay time constant shifted significantly from ~1 ms to >12 ms around 5 ms.
- This component was present in normal hearing ears but absent in cases of cochlear deafness.
Conclusions:
- The slow-decaying component suggests a nonlinear cochlear mechanism, likely mechanical.
- This finding supports a cochlear reflection hypothesis for auditory signal processing.
- The auditory phenomenon is dependent on the normal functioning of cochlear transduction.