Binaural masking level difference for speech signals in noise

Area of Science:

• Audiology
• Psychoacoustics
• Speech Perception

Background:

• The binaural masking level difference (BMLD) is a phenomenon where hearing in noise is better with two ears than one.
• Understanding BMLD is crucial for developing effective hearing aids and auditory rehabilitation strategies.
• Investigating the impact of interaural phase differences on BMLD can reveal more about binaural hearing mechanisms.

Purpose of the Study:

• To investigate the effect of a 180-degree interaural phase shift on speech detection and recognition thresholds.
• To quantify the binaural intelligibility level difference (BILD) under these specific binaural conditions.
• To explore the relationship between speech intelligibility and the BILD in normally hearing individuals.

Main Methods:

• 10 normally hearing subjects participated in the study.
• Swedish spondaic words were used as speech stimuli, masked by noise.
• Stimuli were presented binaurally with a 180-degree phase shift between the left and right ears.
• Speech detection and recognition thresholds were measured, along with speech intelligibility as a function of BILD.

Main Results:

• A 180-degree phase shift of the speech signal between the ears significantly improved speech detection thresholds.
• Speech intelligibility also showed improvement under the tested phase-shifted condition.
• The measured binaural intelligibility level difference (BILD) ranged from 5.7 to 7.7 dB.

Conclusions:

• A 180-degree interaural phase difference can enhance speech detection and intelligibility in noise for normally hearing listeners.
• The observed BMLD effect suggests that specific interaural phase manipulations can leverage binaural hearing advantages.
• These findings contribute to a deeper understanding of binaural unmasking and have implications for auditory signal processing.