A NEW MODEL OF HEARING AND ITS PERFORMANCE IN PITCH PERCEPTION (COCHLEAR MODELING, AUDITORY)

This thesis attempts to introduce a new concept of the human hearing process and to evaluate its ability to explain a number of pitch related anomalies. This concept assigns functionalities to events beyond the displacement of the basilar membrane by taking into account two kinds of wave propagation in the human cochlea. The new concept has provided the basis for a computational model of the cochlea.; The objective of this thesis is to present a model that is a first order global approximation to the cochlear functions, as an aid to the understanding of the human auditory system. A brief study of the anatomy and physiology of the ear provides a starting point in this venture. The model is derived based on assumptions well supported by physiological and psychoacoustic data found in the literature. The performance of the model is evaluated from a software implementation, in simulated experiments related to the perception of pitch.; The qualitative agreement of the response of the model to simple acoustic stimuli like clicks and pure tones with the corresponding observed neural and psychoacoustic data is remarkable. A new theory called the "subharmonic" theory that has evolved from the model predicts the correct shift of the "residue" pitch, obviating the need for the "second" effect of pitch shift. The model also exhibits a nonlinear behavior by producing distortion products like the "combination tone" and the "difference tone" and offers an adequate explanation of their origins. Tonal masking is another area where the model's response matches data seen in the literature.; This attempt has given rise to a new interpretation of the cochlear functions. It is hoped that the insight thus gained can be usefully applied to related fields like speech recognition.