Threshold differences for interaural time delays carried by double vowels

Area of Science:

• Auditory Neuroscience
• Psychoacoustics
• Speech Perception

Background:

• Interaural time differences (ITDs) are critical cues for sound localization in humans.
• Understanding how competing sounds affect ITD perception is essential for explaining real-world auditory processing.

Purpose of the Study:

• To investigate the impact of a simultaneous distractor vowel on the perception of target vowel ITDs.
• To evaluate the performance of auditory models in predicting these effects.

Main Methods:

• Participants detected a target vowel in the presence of a fixed-ITD distractor vowel.
• Threshold ITDs for the target vowel were measured under various conditions (vowel pairs, levels, fundamental frequencies).
• A multichannel auditory model was adapted and tested against the experimental data.

Main Results:

• Threshold ITDs for the target vowel were significantly larger when presented with a distractor compared to alone.
• The magnitude of this effect varied with vowel type, relative intensity, and fundamental frequency differences.
• The multichannel model partially predicted the observed effects, particularly those related to level.

Conclusions:

• The presence of a competing sound significantly alters the perception of ITDs for a target sound.
• A modified single-channel auditory model, incorporating fundamental frequency information, provided a better qualitative fit to the data than the multichannel model.
• These findings highlight the complexity of binaural processing in the presence of multiple, simultaneous auditory objects.