Spatial Hearing at the Cocktail Party
Spatial hearing has long been appreciated to aid in hearing out a signal amid a crowd of competing sounds, like the task of following a conversation at a noisy cocktail party. Nevertheless, objective psychophysical measures have yielded conflicting results, with some studies showing only weak effects of spatial separation when listeners are asked to integrate information across sources. In contrast, we find a robust spatial effect in a task in which listeners must segregate interleaved sound sequences, like the task of that cocktail-party guest. I will present results of psychophysical measures of spatial stream segregation in humans and cats. I also will present recordings from primary auditory cortex showing that single neurons can synchronize preferentially to one or the other of two interleaved sound sequences with spatial acuity comparable to that of psychophysical listeners. I will argue that spatial stream segregation is a largely bottom-up process that results in multiple distinct populations of mutually synchronized neurons and that the perceptual task of selecting an auditory object of attention is a top-down process of selection among those populations.
