Detection of sinusoidal amplitude modulation at unexpected rates

Area of Science:

• Auditory perception
• Psychoacoustics
• Signal detection theory

Background:

• Auditory system's ability to detect amplitude modulation (AM) is crucial for speech and music perception.
• Previous research focused on expected modulation rates, leaving a gap in understanding detection at unexpected rates.

Purpose of the Study:

• To investigate how listener expectation of a target modulation rate influences the detectability of sinusoidal amplitude modulation at other, unexpected rates.
• To assess the impact of listener expectation on auditory modulation detection performance.

Main Methods:

• A probe-signal method was employed with three listeners.
• Listeners were habituated to expect a specific target modulation rate (4, 32, or 256 Hz).
• Sensitivity to modulation at six other unexpected rates was measured using occasional probe signals, with random modulation phase and overall sound level variation.

Main Results:

• Detection performance at unexpected rates was dependent on the cued target rate.
• When expecting 4 Hz, listeners detected modulation across all tested rates.
• When expecting 32 or 256 Hz, higher unexpected rates (≥16 Hz) were detected well (80-90%), but lower rates (<16 Hz) were detected near chance levels.

Conclusions:

• Listener expectation significantly influences the detection of sinusoidal amplitude modulation at unexpected rates.
• Current models of modulation detection do not fully account for the observed effects of expectation.
• Findings highlight the role of predictive coding in auditory perception of temporal modulations.