We continue our studies of cochlear mechanisms in the cat and chinchilla, with emphasis on single cochlear nerve fiber responses to periodic stimuli. Our research includes studies of the temporal structure of the responses to steady state and transient stimuli, and of the spatial distribution of response activity over hundreds of cochlear nerve fibers in the same animal. Our approach is highly quantitative and makes extensive use of mathematical models to guide our experimental studies and interpret their results. We are particularly interested in the analysis of nonlinear phenomena in the cochlea, the indentification of the mechanisms producing them, and the understanding of their functional role in hearing. Although it is sometimes necessary to use abstract and phenomenological models for initial studies, it is our goal to devlop models that are as specific as practical about the mechanisms that they describe. We expect that our work will help to provide an integrated framework for the interpretation of more direct observations of cochlear mechanics and transduction mechanisms, and a useful basis for establishing the consistency of observations using diverse methods. Our current research has the primary goal of integrating observations of cochlear nerve activity, cochlear "reflections" observed in the ear canal sound pressure, results of psychophysical studies, and electrical potentials observed with gross electrodes. The use of a nonlinear two-dimensional computational model to interpret these diverse observations is currently a central focus of this research.