The effect of symmetric and asymmetric directional binaural listening on speech understanding with surrounding cocktail party noise

Abstract

The development of new augmenting hearing devices is reducing the separation between smart listening technologies and hearing aids. They both alter the way people perceive surrounding acoustic sources. One of their common goals is reducing the effect of noisy or crowded environments on listening capabilities. However, it is still unclear how much spatial processing, i.e. conditioning sounds depending on their direction of arrival, can be beneficial to binaural feedback. This study investigates the effect of binaural symmetrical and asymmetrical spatial processing on speech comprehension in a noisy environment, when the listeners are people with no hearing impairment. 15 participants sat at the center of four speakers positioned at 0°, 90°, 180° and 270°, listening and repeating full sentences coming from the speakers, while a competing cocktail party noise was reproduced. The task was repeated in four listening conditions: Free ear, Omnidirectional, Directional and Asymmetric, which differed by the presence and kind of spatial processing performed by a pair of glasses equipped with microphone arrays. We found that Directional and Asymmetric fittings performed similarly for frontal sources, but were significantly more effective than Free ear and Omnidirectional. Then, Asymmetric condition showed to be better than Directional for speech coming from one of the sides, but worse than Omnidirectional and Free ear. Overall, asymmetrical fitting could be exploited by augmenting hearing devices to ease communication with multiple talkers in noisy environments or to exclude or reduce the impact of unwanted noise coming from specific directions.