Chapter 5 Auditory Localization Using Spectral Information

Introduction Human hearing is concerned with the perception and interpretation of sensory input to the ears. Such perception may be classiied as auditory events as opposed to sound events 5-1]. A sound event is the physical phenomenon of mechanical vibration which can characterize a sound source, while an auditory event is the brain's perception of an auditory phenomenon which may or may not be due to a sound event. The brain's auditory perception of the world around us is based on the cause-eeect relationships that exist between most sound events and auditory events. The brain perceives sound sources by associating them with auditory events. Auditory function is carried out by the auditory system which culminates in the auditory cortex in the brain. 1 2 CHAPTER 5. AUDITORY LOCALIZATION The complex electromechanical and electrochemical signal processing scheme that constitutes our auditory system thus enables us to perceive sound events as auditory events and interpret them according to the visual world around us. We are able to follow and segregate sound streams by their frequency content, timbre and pitch. However, this ability is considerably enhanced by the functional capability of the human auditory system to localize and track a sound source. Auditory localization is the phenomenon by which we perceive sound sources to be at speciic locations relative to our pose. Auditory localization is an aspect of the interpretation of auditory events which enables the brain to build an auditory scene of the immediate environment and associate it with the visual picture that is acquired simultaneously by the human visual system. The human auditory system has been shown to possess remarkable abilities in localizing and tracking of sound sources 5-1, 5-2, 5-3, 5-4]. This phenomenon has been the subject of intensive multidisciplinary research for several decades. Several theories have been suggested to explain the neural signal processing that could take place in the process of localization. Such modeling has been restricted by the complexity of the auditory system. Many tantalizing riddles still remain unexplained by most of these models. Such phenomena include localization in the medial saggital plane, which is the ability that humans have to localize sounds that are at diierent elevations but are equidistant from either ear, or the cocktail party eeect, a phenomenon where a listener is simultaneously able to localize and separate a number of conversations , and to attend at will to any one of them. Various …