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Preface to the First Edition
This text is, in part, an outgrowth of my graduate course on speech signal processing,
which I have been teaching at the University of Texas at Dallas since the fall of 1999.
It is also, in part, a product of my own research in the area. The fact that no textbook
existed at the time on speech enhancement, other than a few edited books suitable for
the experts, made it difcult to teach the fundamental principles of speech enhance-
ment in a graduate-level course. It must be equally frustrating for new students or
speech scientists interested in getting into the eld of speech enhancement without
having access to a tutorial review or introductory paper (the last review paper was
published in the Proceedings of IEEE in 1979 by Lim and Oppenheim). That work
provided the initial motivation to write this book. My interest in this area stems from
my research to develop noise reduction algorithms that can be used to help hearing-
impaired listeners (cochlear implant listeners) better communicate in noisy environ-
ments.* Crucial to the development of such noise reduction algorithms is the basic
understanding of the limitations and potential of existing enhancement algorithms,
which I believe this book provides.
The textbook consists of 11 chapters, which are outlined in detail in Chapter 1
(Introduction). It is divided into three main parts. Part I presents the digital-signal
processing and speech-signal fundamentals needed to understand speech enhance-
ment algorithms. Part II presents the various classes of speech enhancement algo-
rithms proposed over the past two decades, and Part III presents the methods and
measures used to evaluate the performance of speech enhancement algorithms.
The text body is supplemented with examples and gures designed to help the
reader understand the theory. The book is accompanied by a DVD-ROM, which
contains a speech corpus appropriate for quality and intelligibility evaluation of
processed speech, and MATLAB
®
code with the implementation of major speech
enhancement algorithms. It is my strong belief that having access to MATLAB code
and a common speech database against which to evaluate new speech enhancement
algorithms is crucial and necessary in order to move the eld forward. Appendix C
provides a detailed description of the contents of the DVD-ROM.
The book can be used as a textbook for a one-semester graduate-level course on
speech enhancement. Necessary prerequisites for such a course would be a course
on digital signal processing and fundamental knowledge of probability theory, ran-
dom variables, and linear algebra. This book can also be used as a supplement to an
introductory course on speech processing. In this case, Chapters 4 through 8 could
be covered along with a select set of sections from Chapters 9 and 10.
I wish to express my sincere thanks to the many colleagues and graduate stu-
dents who contributed in some way to the writing of this book. I would like to
thank Professors Patrick Wolfe, Kuldip Paliwal, Peter Assmann, John Hansen, and
*
This work is supported by the National Institutes on Deafness and Other Communication Disorders,
NIH.