We are surrounded by noise; to separate the signals we want to hear from those we do not we have developed various strategies. Giving computers similar abilities would help develop devices such as intelligent hearing aids. This book reviews new and recent work on the modelling of auditory processes.

The full power of combining experiment and theory has yet to be unleashed on studies of the neural mechanisms in the brain involved in acoustic information processing. In recent years, enormous amounts of physiological data have been generated in many laboratories around the world, characterizing electrical responses of neurons to a wide array of acoustic stimuli at all levels of the auditory neuroaxis. Modern approaches of cellular and molecular biology are leading to new understandings of synaptic transmission of acoustic information, while application of modern neuro-anatomical methods is giving us a fairly comprehensive view ofthe bewildering complexity of neural circuitry within and between the major nuclei of the central auditory pathways. Although there is still the need to gather more data at all levels of organization, a ma jor challenge in auditory neuroscience is to develop new frameworks within which existing and future data can be incorporated and unified, and which will guide future laboratory ex perimentation. Here the field can benefit greatly from neural modeling, which in the central auditory system is still in its infancy. Indeed, such an approach is essential if we are to address questions related to perception of complex sounds including human speech, to the many di mensions of spatial hearing, and to the mechanisms that underlie complex acoustico-motor behaviors.

A message from a speaker to a listener has to travel a very long way, from an intention on the part of the former, via an acoustic signal, through the transducer stages of the peripheral auditory system. The present book is about the listener. It consists of 35 papers by researchers from a limited number of related fields between the auditory periphery and word recognition, who met in 1991.

A new modeling approach of the "effective" signal processing in the auditory system was developed which describes effects of spectral and temporal integration in amplitude-modulation detection and masking. Envelope fluctuations within each auditory channel are analyzed with a modulation filterbank. The parameters of the filterbank are the same for all auditory filters and were adjusted to allow the model to account for modulation detection and modulation masking data with narrowband carriers at a high center frequency. In the detection stage, the outputs of all modulation filters from all excited peripheral channels are combined linearly with optimal weights. To integrate information across time, a "multiple-look" strategy is implemented within the detection stage which allows the model to account for long time constants derived from the data on modulation integration without introducing true long-term integration. Model predictions are compared with both own experimental results and with experimental data from the literature. A large variety of psychoacoustical experiments can be well described by the model. This supports the hypothesis that amplitude fluctuations are processed by modulation-frequency-selective channels. The model might also be used in applications such as psychoacoustical experiments with hearing-impaired listeners, speech intelligibility and speech quality predictions. engl.

Although speech is the primary behavioral medium by which humans communicate, its auditory basis is poorly understood, having profound implications on efforts to ameliorate the behavioral consequences of hearing impairment and on the development of robust algorithms for computer speech recognition. In this volume, the authors provide an up-to-date synthesis of recent research in the area of speech processing in the auditory system, bringing together a diverse range of scientists to present the subject from an interdisciplinary perspective. Of particular concern is the ability to understand speech in uncertain, potentially adverse acoustic environments, currently the bane of both hearing aid and speech recognition technology. There is increasing evidence that the perceptual stability characteristic of speech understanding is due, at least in part, to elegant transformations of the acoustic signal performed by auditory mechanisms. As a comprehensive review of speech's auditory basis, this book will interest physiologists, anatomists, psychologists, phoneticians, computer scientists, biomedical and electrical engineers, and clinicians.