Coherence masking protection in brief noise complexes: effects of temporal patterns

Area of Science:

• Auditory perception
• Psychoacoustics
• Signal processing

Background:

• Listeners' ability to discern a target signal's pitch is often impaired by masking noise.
• Auditory object formation is crucial for segregating sound sources and understanding complex auditory scenes.
• Coherence masking protection, previously observed in vowel perception, suggests temporal synchrony aids signal identification.

Purpose of the Study:

• To investigate the influence of a spectrally separated cosignal on listeners' pitch classification thresholds for a target signal in noise.
• To determine the role of temporal synchrony (onset and offset) between the target signal and cosignal in auditory object formation and masking protection.
• To explore whether general auditory mechanisms for perceptual integration apply to both speech and nonspeech auditory stimuli.

Main Methods:

• Three experiments were conducted using narrow bands of noise as target signals and a low-pass filtered noise as the masker.
• A spectrally distinct cosignal was introduced with varying temporal relationships (synchronous, leading, lagging) to the target signal.
• Listeners' identification thresholds for the target signal's pitch were measured under different conditions.

Main Results:

• Identification thresholds were significantly lower when the target signal and cosignal were temporally synchronous (onset and offset), a phenomenon termed coherence masking protection.
• The masking protection effect diminished when the cosignal led or lagged the target signal.
• Either onset or offset synchrony was sufficient for protection when the cosignal was longer; only onset synchrony sufficed when the target signal was longer, indicating unequal contributions to auditory object formation.

Conclusions:

• Temporal synchrony between a target signal and a spectrally separate cosignal enhances pitch identification by facilitating auditory object formation.
• The findings support the hypothesis that speech perception utilizes general auditory mechanisms for perceptual integration, as demonstrated with nonspeech stimuli.
• The duration and temporal relationship of signal components differentially influence the formation of auditory objects.