Extents of laterality and binaural interference effects

Area of Science:

• Auditory perception
• Psychoacoustics
• Spatial hearing

Background:

• Interaural time delays (ITDs) are crucial cues for sound localization.
• Previous research indicated spectrally remote sounds can reduce sensitivity to ITDs in target tones.
• Sinusoidally amplitude-modulated (SAM) tones are commonly used in auditory research.

Purpose of the Study:

• To investigate the influence of spectrally remote diotic SAM tones on the perceived laterality of a 4-kHz SAM target tone with ITDs.
• To determine if the lateral position shift caused by remote tones affects tasks beyond simple ITD detection or discrimination.
• To evaluate the predictive power of a weighted-combination model incorporating laterality and discriminability measures.

Main Methods:

• Listeners performed an acoustic pointing task to measure perceived laterality.
• A 4-kHz SAM target tone with varying ITDs was presented with or without spectrally remote diotic SAM tones.
• Stimuli were 100% modulated at 250 Hz, 77 dB SPL, and 250 ms duration.

Main Results:

• Spectrally remote, diotic SAM tones caused the 4-kHz target tone to be perceived closer to the midline, even with ITDs up to 600 microseconds.
• Observed changes in lateral position did not fully explain interference effects in prior discrimination tasks.
• An augmented weighted-combination model reasonably predicted interference in discrimination tasks.

Conclusions:

• The perceived location of a sound can be significantly influenced by spectrally remote auditory information.
• The effects of spectrally remote sounds on auditory perception extend to spatial judgments, not just detection/discrimination.
• Auditory models incorporating both laterality and discriminability are necessary for accurate prediction of complex auditory phenomena.