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Effects of envelope-vocoder processing on F0 discrimination and concurrent-vowel identification
Michael K Qin1, Andrew J Oxenham
1Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA. qin@nsmrl.navy.mil
Ear and Hearing
|October 19, 2005
Summary
Envelope-vocoder processing impairs fundamental frequency (F0) discrimination, especially in reverberation. Even with good F0 difference limens, listeners struggle to use F0 cues for concurrent vowel identification.
Area of Science:
- Auditory Perception
- Speech Processing
- Signal Processing
Background:
- Envelope-vocoder processing is used to simulate hearing device signal processing.
- Fundamental frequency (F0) differences are crucial for speech intelligibility and source segregation.
- Reverberation significantly degrades auditory signal quality.
Purpose of the Study:
- To investigate how envelope-vocoder processing affects F0 discrimination in varying reverberation.
- To assess the impact of vocoder channels on concurrent vowel identification using F0 cues.
Main Methods:
- Measured F0 difference limens (F0DLs) with different numbers of vocoder channels and simulated reverberation.
- Evaluated concurrent vowel identification based on F0 differences with varying vocoder channels.
Main Results:
- Reverberation impaired F0 discrimination, particularly with fewer vocoder channels.
- Despite measurable F0DLs, listeners could not utilize F0 differences for concurrent vowel identification.
Conclusions:
- Vocoder processing's poor spectral representation of low harmonics limits F0 information transfer.
- Temporal envelope F0 cues are weak, susceptible to reverberation, and insufficient for source segregation.
- Cochlear implant users may not benefit from F0 differences in complex listening environments.
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