Nonlinear Coc 3 . Nonlinear Cochlear Signal Processingand Masking in Speech PerceptionJ

There are many classes of masking, but two major classes are easily defined: neural masking and dynamic masking. Neural masking characterizes the internal noise associated with the neural representation of the auditory signal, a form of loudness noise. Dynamic masking is strictly cochlear, and is associated with cochlear outerhair-cell processing. This form is responsible for dynamic nonlinear cochlear gain changes associated with sensorineural hearing loss, the upward spread of masking, two-tone suppression and forward masking. The impact of these various forms of masking are critical to our understanding of speech and music processing. In this review, the details of what we know about nonlinear cochlear and basilar membrane signal processing is reviewed, and the implications of neural masking is modeled, with a comprehensive historical review of the masking literature. This review is appropriate for a series of graduate lectures on nonlinear cochlear speech and music processing, from an auditory point of view. 3.1 Basics .................................................. 27 3.1.1 Function of the Inner Ear .............. 28 3.1.2 History of Cochlear Modeling ......... 31