Masked threshold changes associated with angular separation of noise and signal sources

Area of Science:

• Auditory Neuroscience
• Psychoacoustics
• Signal Processing

Background:

• Understanding auditory spatial perception is crucial for diagnosing hearing impairments.
• The head shadow effect, a binaural phenomenon, influences sound localization and detection.
• Investigating the role of head shadow in masking release is essential for auditory models.

Purpose of the Study:

• To quantify threshold changes for pure tones and click trains at varying spatial separations between signal and masker.
• To determine the influence of the head shadow effect on masked thresholds at different frequencies.
• To evaluate the relevance of cross-correlation models in explaining binaural masking release.

Main Methods:

• Determined masked hearing thresholds for 0.5, 1, and 8 kHz pure tones and click trains.
• Varied the angular separation between the signal source and a white noise masker from 0 to 90 degrees.
• Assessed the impact of ear occlusion on masked thresholds for click train stimuli.

Main Results:

• No significant threshold changes were observed for 0.5 and 1 kHz pure tones.
• Masked thresholds for 8 kHz pure tones and click trains decreased linearly with increasing angular separation (9 dB and 13 dB, respectively).
• Occluding the ear directed towards the masker did not significantly alter click train masked thresholds, indicating a head shadow effect.

Conclusions:

• Threshold improvements at high frequencies and for click trains are primarily attributed to the head shadow effect.
• The head shadow effect, by reducing noise on the shielded side, enhances signal detection.
• These findings suggest that cross-correlation techniques may be less critical for signal detection in noise than previously thought.