The perceptual organization of speech: Contributions of general and speech-specific factors

Spoken communication is a fundamental human activity. However, it is fairly uncommon in everyday life for us to hear the speech of a single talker in the absence of other background sounds, and so our auditory system is faced with the challenge of grouping together those sound elements that come from one source and segregating them from those arising from other sources. Without a solution to this auditory scene analysis problem, our perceptions of speech and other sounds would not correspond to the events that produced them. The fact that we can focus our attention on one person speaking in the presence of other talkers indicates that our auditory perceptual system is generally successful at grouping together the sound elements from a source in a complex auditory scene, and segregating them from other sound sources, but our understanding of how this is achieved remains limited. Most research on auditory scene analysis has focused on relatively simple sounds and has identified a number of general principles for the grouping of sound elements. However, at least as currently understood, these principles seem inadequate to explain the perceptual grouping of speech, because speech has acoustic properties that are diverse and rapidly changing. Furthermore, speech is a highly familiar stimulus, and so our auditory system has had the opportunity to learn about speech-specific properties that may assist in the successful perceptual grouping of speech. The aim of this project is to explore how much of our ability to segregate a talker's speech from a sound mixture depends on general-purpose auditory grouping principles that are applicable to all sounds, and how much depends on grouping principles that are specific to speech sounds. The approach is to generate artificial speech-like stimuli with precisely controlled properties, to mix target utterances with carefully designed competitors that offer alternative grouping possibilities, and to measure how manipulating the acoustic properties of these competitors affects the ability of listeners to recognize the target utterance in the mixture. The results of this project will improve our understanding of the perceptual organization of speech and suggest ways to improve the performance of devices such as hearing aids and automatic speech recognizers when they are operating in noisy environments.