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Fundamental frequency-dependent changes in vowel-evoked envelope following responses
Vijayalakshmi Easwar1, Sriram Boothalingam1, Regan Flaherty1
1Department of Communication Sciences and Disorders, University of Wisconsin-Madison, United States; Waisman Center, University of Wisconsin-Madison, United States.
Hearing Research
|July 6, 2021
Summary
Scalp-recorded envelope following responses (EFRs) reveal that a small increase in voice fundamental frequency (f0) significantly reduces EFR amplitude, phase coherence, and signal-to-noise ratio, independent of spectral changes.
Area of Science:
- Auditory Neuroscience
- Speech Perception
- Neurophysiology
Background:
- Scalp-recorded envelope following responses (EFRs) are a non-invasive measure of auditory encoding.
- Voice fundamental frequency (f0) is crucial for speech understanding.
- Previous studies haven't isolated f0's effect on EFRs from spectral variations.
Purpose of the Study:
- To investigate the independent effect of voice f0 on EFRs.
- To control for vowel formant characteristics and neural generator changes.
- To quantify the impact of f0 variations on EFR amplitude, phase coherence, and SNR.
Main Methods:
- EFRs were elicited using a male-spoken vowel /u/ and a version with lowered f0.
- Vowel stimuli had matched formant characteristics and were presented to young adults with normal hearing.
- EFRs were recorded using vertex-nape and vertex-ipsilateral mastoid montages.
Main Results:
- An 8.5 Hz increase in f0 reduced EFR amplitude by 25 nV.
- Phase coherence decreased by 0.05 and SNR by 3.5 dB with increased f0.
- These reductions were consistent across ears and electrode montages.
Conclusions:
- Voice f0 significantly impacts EFRs even when spectral characteristics are controlled.
- Findings help differentiate the contributions of f0 and spectral content to EFRs.
- This research clarifies the role of f0 in auditory processing assessed via EFRs.
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