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Modeling interaural-delay sensitivity to frequency modulation at high frequencies
1Massachusetts Institute of Technology, Research Laboratory of Electronics, Cambridge 02139, USA. kourosh@caltech.edu
The Journal of the Acoustical Society of America
|May 30, 1998
Summary
This study investigated auditory sensitivity to frequency-modulated (FM) and amplitude-modulated (AM) tones, finding optimal detection rates for FM tones at higher frequencies than AM tones. Sensitivity improved with increased modulation depth for both tone types.
Area of Science:
- Auditory Neuroscience
- Psychoacoustics
- Signal Processing
Background:
- Interaural time differences are crucial for sound localization.
- Sensitivity to amplitude and frequency modulation provides insights into auditory processing mechanisms.
Purpose of the Study:
- To compare interaural-delay sensitivity to high-frequency sinusoidal frequency-modulated (SFM) tones versus sinusoidal amplitude-modulated (SAM) tones.
- To investigate the effects of modulation rate and depth on SFM and SAM tone perception.
- To explore binaural fusion and lateralization of hybrid SFM-SAM signals.
Main Methods:
- Thresholds for SFM and SAM tones were measured across various modulation rates (25-800 Hz) and depths (-12 to 18 dB).
- Bandpass noise was used to constrain auditory filters.
- A nonstationary stochastic model of binaural interaction was employed for data prediction.
Main Results:
- Both SFM and SAM tone sensitivity functions exhibited U-shaped curves, with optimal SFM sensitivity at higher rates (200-400 Hz) than SAM tones (100-200 Hz).
- Thresholds consistently improved with increased modulation depth for both modulation types.
- Hybrid SFM-SAM signals could be perceived as fused and lateralized when modulation rates were matched.
Conclusions:
- Auditory system exhibits distinct optimal processing rates for frequency versus amplitude modulation.
- Modulation depth significantly impacts the detection of both SFM and SAM tones.
- Binaural processing can integrate spectrally distinct but temporally synchronized auditory signals.