Perhaps audio signal processing is perceived as an easier and less dynamic subject than video signal processing, judging from the relative numbers of books in these two areas. This book, which is at the cutting edge of audio processing technology, shows that this technology is instead quite involved, and has a fair amount of dynamic momentum. The book’s purpose is to make available to a broad audience the latest developments in audio signal processing techniques, as applied to multimedia communications.

Delving further into the different studies presented in the book, one cannot help but find similarities to, if not exact reproductions of, entire chapters from another book, published four years ago by almost the same authors and the same publisher, but with a slightly different title [1]. For example, chapter 2 of this book, on superdirectional microphone arrays, was just copied; take any sentence at random from chapter 10 in the previous book, and it will match with the corresponding sentence in chapter 2 of the new book. Perhaps even a slight change, like not only mentioning the initial superdirectivity results by Ouzkov from some 60 years ago, but also reproducing them, and providing their physical explanation, would be more than beneficial. Without such explanations, many readers (those without access to these papers) will continue to find superdirectivity to be a blurry concept, justified only by clever formula manipulations. Mentioning optimal array processing in connection with superdirectivity, as well as some real product examples (for example, PictureTel’s videoconferencing systems), would also provide more practical ground for the results of this chapter.

Chapter 2 is followed by a chapter on spherical microphone arrays, fortunately absent in the previous book. Unfortunately, with the very next chapter, we again find contents copied from the old book. The chapter, “Subband Noise Reduction Methods for Speech Enhancement,” is, in fact, chapter 9 from the older book. Chapter 5 discusses methods for multichannel echo cancellation, and, although it is not a copy from the previous book, it is quite close in content.

At chapter 6, a natural question starts to emerge: Why was this book published as a new book, and not as a second printing of the old one, with the very few differences confined to supplementary appendices, or to a separate book? The reason for that question is that chapter 6 is a copy of chapter 5 from the older book. The chapter’s theme is double-talk detection, a crucial component of acoustic echo cancellers. The text is an expanded and enhanced version of a research paper on the topic published several years ago [2].

Chapter 7 is new, and addresses the challenges of implementing a real-time echo canceller on a personal computer (PC) platform. Although it is interesting and innovative, the authors’ solution is not unique, and similar results have been observed on prototype PictureTel products, using full duplex sound cards and a simple passive external box, the size of a matchbox, to essentially reroute the signals, and thus evade the unpredictability of operating system (OS) sound buffer manipulations.

Chapters 9 and 10 exist in different form in the older book. Chapter 9 discusses source localization with microphones, and chapter 10 discusses blind source separation for convolutive mixtures. Chapter 8 is new, and introduces time delay estimation. Here again, a real product example would be beneficial, since both PictureTel and Polycom videoconferencing products use camera steering-based acoustic source localization principles (and, of course, time delay estimation). Chapter 11 provides a succinct and refreshing overview of audio coding. Chapter 12 introduces sound field synthesis topics, and also provides a good overview of listening room and loudspeaker compensation techniques. The final chapter, on virtual spatial sound, is more descriptive than analytical, in contrast with the two chapters on the same topic in the previous book.

Overall, the reader is presented with a book on the state of the art of audio technology, with technical contents that are near perfection in most cases. However, given the fact that most of the book was published several years ago, in a similar book by almost the same authors, I would personally rather borrow it than buy it.