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Mcloughlin I. Applied Speech and Audio Processing. With Matlab Examples

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Mcloughlin I. Applied Speech and Audio Processing. With Matlab Examples
Издательство Cambridge University Press, 2009, -218 pp.
Speech and hearing are closely linked human abilities. It could be said that human speech is optimised toward the frequency ranges that we hear best, or perhaps our hearing is optimised around the frequencies used for speaking. However whichever way we present the argument, it should be clear to an engineer working with speech transmission and processing systems that aspects of both speech and hearing must often be considered together in the field of vocal communications. However, both hearing and speech remain complex subjects in their own right. Hearing particularly so.
In recent years it has become popular to discuss psychoacoustics in textbooks on both hearing and speech. Psychoacoustics is a term that links the words psycho and acoustics together, and although it sounds like a description of an auditory-challenged serial killer, actually describes the way the mind processes sound. In particular, it is used to highlight the fact that humans do not always perceive sound in the straightforward ways that knowledge of the physical characteristics of the sound would suggest.
There was a time when use of this word at a conference would boast of advanced knowledge, and familiarity with cutting-edge terminology, especially when it could roll off the tongue naturally. I would imagine speakers, on the night before their keynote address, standing before the mirror in their hotel rooms practising saying the word fluently. However these days it is used far too commonly, to describe any aspect of hearing that is processed nonlinearly by the brain. It was a great temptation to use the word in the title of this book.
The human speech process, while more clearly understood than the hearing process, maintains its own subtleties and difficulties, not least through the profusion of human languages, voices, inflexions, accents and speaking patterns. Speech is an imperfect auditory communication system linking the meaning wishing to be expressed in one brain, to the meaning being imparted in another brain. In the speaker’s brain, the meaning is encoded into a collection of phonemes which are articulated through movements of several hundred separate muscles spread from the diaphragm, through to the lips. These produce sounds which travel through free air, may be encoded by something such as a telephone system, transmitted via a satellite in space half way around the world, and then recreated in a different environment to travel through free air again to the outer ears of a listener. Sounds couple through the outer ear, middle ear, inner ear and finally enter the brain, on either side of the head. A mixture of lower and higher brain functions then, hopefully, recreate a meaning.
It is little wonder, given the journey of meaning from one brain to another via mechanisms of speech and hearing, that we call for both processes to be considered together. Thus, this book spans both speech and hearing, primarily in the context of the engineering of speech communications systems. However, in recognition of the dynamic research being undertaken in these fields, other areas are also drawn into our discussions: music, perception of non-speech signals, auditory scene analysis, some unusual hearing effects and even analysis of birdsong are described.
It is sincerely hoped that through the discussions, and the examples, the reader will learn to enjoy the analysis and processing of speech and other sounds, and appreciate the joy of discovering the complexities of the human hearing system. In orientation, this book is unashamedly practical. It does not labour long over complex proofs, nor over tedious background theory, which can readily be obtained elsewhere. It does, wherever possible, provide practical and working examples using Matlab to illustrate its points. This aims to encourage a culture of experimentation and practical enquiry in the reader, and to build an enthusiasm for exploration and discovery. Readers wishing to delve deeper into any of the techniques described will find references to scientific papers provided in the text, and a bibliography for further reading following each chapter.
Although few good textbooks currently cover both speech and hearing, there are several examples which should be mentioned at this point, along with several narrower texts. Firstly, the excellent books by Brian Moore of Cambridge University, covering the psychology of hearing, are both interesting and informative to anyone who is interested in the human auditory system. Several texts by Eberhard Zwicker and Karl D. Kryter are also excellent references, mainly related to hearing, although Zwicker does foray occasionally into the world of speech. For a signal processing focus, the extensive Gold and Morgan text, covering almost every aspect of speech and hearing, is a good reference.
Introduction
Basic audio processing
Speech
Hearing
Speech communications
Audio analysis
Advanced topics
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