Improving Multitalker Speech Communication with Advanced Audio Displays

Historically, most of the metrics that have been used to evaluate the effectiveness of military communications systems have focused on measuring the intelligibility of a single talker in the presence of a continuous noise masker. However, many critical military operations involve complex communications tasks that require listeners to monitor, process, and respond to two or more simultaneous speech signals. Many factors can influence performance in such tasks, including the relative levels of the competing talkers, the similarities between the voices of the competing talkers, and, in audio displays that allow the different channels of speech to be spatially separated, the apparent locations of the target and masking voices. In this paper, we present an overview of the factors that can influence speech intelligibility in multitalker listening environments, and compare and contrast them to the factors that influence intelligibility in the speech-in-noise situations that are usually used to evaluate military communications systems. We also discuss the intelligibility benefits that can be achieved with advanced audio displays that use either dichotic or binaural processing to spatially separate the apparent locations of multiple simultaneous channels of speech. Finally, we describe a spatial configuration that has been shown to maximize the benefit of spatial separation in a listening configuration with up to seven simultaneous speech signals.