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Effect of inter-aural temporal envelope differences on inter-aural time difference thresholds for amplitude modulated
Vibha Kanagokar1, Hasna Fathima1,2, Jayashree Sunil Bhat3
1Department of Audiology and Speech Language Pathology, Kasturba Medical College, Mangalore, Manipal Academy of Higher Education, Manipal, Karnataka, India.
Codas
|February 7, 2024
Summary
Inter-aural differences in modulation depth negatively impact the perception of inter-aural time difference (ITD) for amplitude-modulated noise. This finding is crucial for understanding auditory spatial processing, especially in challenging listening conditions.
Area of Science:
- Auditory Neuroscience
- Psychoacoustics
- Signal Processing
Background:
- Inter-aural time difference (ITD) and inter-aural level difference (ILD) are critical for sound localization and spatial hearing.
- These cues rely on binaural coherence, the similarity of spectro-temporal information between ears.
- Inter-aural modulation depth differences can degrade binaural coherence, impacting ITD/ILD encoding, particularly in noisy or reverberant environments, or with hearing assistive devices.
Purpose of the Study:
- To investigate how inter-aural modulation depth differences affect the thresholds for perceiving inter-aural time differences (ITD).
- To examine this effect in normal-hearing young adults using amplitude-modulated noise.
Main Methods:
- Participants listened to amplitude-modulated, high-pass filtered noise presented via headphones.
- One ear's modulation depth was fixed at 90%, while the other varied between 90% and 50%.
- Inter-aural time difference (ITD) thresholds were measured for modulation frequencies of 8 Hz and 16 Hz as a function of the inter-aural modulation depth difference.
Main Results:
- A statistically significant increase in ITD thresholds was observed as the inter-aural modulation depth difference increased.
- This effect was consistent for both 8 Hz and 16 Hz modulation frequencies.
Conclusions:
- Inter-aural differences in modulation depth impair the perception of ITD for amplitude-modulated noise.
- These findings highlight the importance of consistent modulation depth between ears for accurate binaural cue encoding and spatial hearing.
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