ZAPlab studies human auditory perception generally, with a focus in sound localization and spatial hearing. Specific areas of interest include: the perception of sound source distance, the contributions of echoes and reverberation to percepts of source direction and distance, and the effects of adaptation, training, and input from other sensory modalities on spatial hearing. Research in ZAPlab relies heavily on auditory display technology that effectively simulates a "virtual" auditory space (VAS) using information about the acoustical characteristics of listeners' external ears and the environment. This technology not only enables the precise study of psychophysical relationships between the acoustic signals present at the two ears and human spatial hearing abilities, but also allows for simulations and scientifically relevant signal manipulations that would be impossible in real listening situations. Two current projects in the lab capitalize on these advantages of VAS technology.
1. Perceptual Processing of Indirect Sound: The processes by which we hear auditory events in most everyday acoustic environments that produce indirect sound (e.g. echoes, reflections, reverberation) are complex and not well understood. Under certain circumstances, indirect sound can facilitate speech communication and certain aspects of sound localization. In other circumstances, however, indirect sound can produce deficits in these and other abilities that can be particularly large for individuals with hearing impairment. Recent results have demonstrated that some aspects of indirect sound processing appear to be affected by previous exposure to the acoustic environment, which suggests a form of perceptual adaptation. Although these adaptation effects can be substantial for situations with a single echo, the effects have not been evaluated in more realistic acoustic environments with complex patterns of indirect sound resulting from multiple echoes and reverberation. The long-term goal of this project is a complete understanding of the mechanisms and the potentially adaptive processes that subserve auditory localization and communication in everyday acoustic environments with complex patterns of indirect sound and the potential impact of hearing loss on these processes. This project uses state-of-the-art VAS technology to simulate and manipulate realistic echoic listening environments. Knowledge gained from these studies will lead to an improved understanding of a significant public health problem: the impairment of communication and localization in acoustically reflective or reverberant environments resulting from hearing loss. [Work supported by NIH-NIDCD R01DC008168; Zahorik, PI]
2. Enhancing the utility of spatial auditory displays for military applications: This project seeks to determine and quantify ways of improving VAS displays, particularly under non-optimal simulation conditions such as when the display is not customized acoustically for an individual operator. One potential way to improve sound localization performance under such display condition is to provide targeted operator training. Here, training techniques for sound localization using other sensory modalities are tested and evaluated. Important questions include the relative importance of the sensory modalities used in training techniques, the amount of training that would be required, and how long the training effects will last. The project also examines ways in which a spatial auditory display might be used to enhance auditory distance perception, which is known to be relatively poor even in real auditory environments, and enhance accurate judgment of moving sound source trajectories. Funding for this project is also supporting the construction of a state-of-the-art anechoic chamber facility at the University of Louisville. [Work supported by AFOSR & KY DEPSCoR FA9550-08-1-0234; Zahorik, PI]