Consequences of cochlear damage for the detection of interaural phase differences

Area of Science:

• Auditory Neuroscience
• Psychoacoustics
• Hearing Science

Background:

• Interaural phase differences (IPDs) are crucial for sound localization.
• Cochlear hearing loss can affect the processing of auditory temporal information.
• The impact of cochlear damage on IPD detection, particularly for carrier versus modulation signals, requires further investigation.

Purpose of the Study:

• To compare the detection thresholds of interaural phase differences (IPDs) in normal-hearing and hearing-impaired listeners.
• To investigate whether IPD detection deficits in cochlear hearing loss differ for carrier signals versus amplitude modulation (AM) signals.
• To explore the relationship between hearing loss, sensation level, and the perception of temporal fine structure.

Main Methods:

• Measured IPD detection thresholds in 7 normal-hearing and 9 hearing-impaired listeners.
• Used sinusoidally amplitude-modulated pure tones with IPDs applied to either the carrier or the modulation.
• Employed a three-interval, two-alternative, forced-choice paradigm at fixed sound pressure levels (75 dB) and various carrier (250-1000 Hz) and modulation (20-50 Hz) frequencies.

Main Results:

• Hearing-impaired listeners had higher average IPD detection thresholds than normal-hearing listeners.
• The deficit was significantly larger for carrier IPDs compared to modulation IPDs in hearing-impaired listeners.
• Reductions in sensation level disproportionately impaired modulation IPD detection more than carrier IPD detection in normal listeners.

Conclusions:

• Cochlear damage leads to a reduced ability to detect interaural phase differences, particularly for the carrier signal.
• The findings suggest that cochlear damage impairs perceptual sensitivity to the temporal fine structure of sounds.
• The differential deficit for carrier versus modulation IPDs highlights specific processing challenges associated with cochlear hearing loss.