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Typesetting by the authors and SPI Publisher Services Coverdesign: Design & Production, Heidelberg Printedonacid-freepaper SPIN: 11412748 62/3100/SPI- 543210 Preface The demand for devices that utilize digital speech processing is constantly growing. The desire to carry out tasks “hands-free” is very often the mo- tivation. Examples are voice controlled technical devices, speech or speaker recognitionsystems,hands-freecommunicationwithremotepartners,systems to ease communication in noisy environments without using close-talking mi- crophones, and to improve the hearing ability of impaired persons, to name only a few. In the majority of these applications, the existence of acoustical echoes and background noise lead to considerable performance degradations. Methods for the cancellation of echoes and the suppression of background noise,therefore,areofhighinteresttodesignersofspeechprocessingsystems. The idea for this book arose immediately after the editors had finished theirbookon“AcousticEchoandNoiseControl”1 sinceanumberofsubjects could not be treated in sufficient detail and some important topics had to be completely omitted. The editors also came to the conclusion that the value of an additional book would be considerably increased if scientists that are internationally recognized for their work on the related topics would report on the state of the art and on their findings. The editors approached most of the authors at EUSIPCO ’2004 and on the spot they agreed to contribute to this project. The editors feel bound to express their sincere thanks to all of them. Not only did they finish their contributions in good time, they also accepted the proposals of the editors with respect to notation of variables and references. Thus, it should be easier for the reader to jump between different chapters. The book is organized in five parts. Part I just contains a brief introduc- tion into acoustic echo and noise control, a few remarks on current research topics,andadescriptionofthecontentsofthebook.PartIIdealswithmulti- microphone processing. Having the outputs of more than one microphone 1 EberhardHa¨nsler andGerhardSchmidt: Acoustic Echo and Noise Control,New York, NY: Wiley, 2004 VI Preface available opens an additional degree of freedom to the designer of speech processing systems. In Part III advanced methods for echo cancellation such as the identifica- tion of sparse impulse responses, selective-tap update, and the application of nonlinearechopathsmodelsarepresented.Attemptsforanintelligentcontrol of hands-free telephones are introduced. Part IV is devoted to noise reduc- tionprocedures.Anin-depthtreatmentofconventionalandofadvancedtime- and frequency-domain methods is given, followed by a model-based approach using Kalman filters. Selected applications of acoustic echo and noise control systems are out- lined in Part V. Auditory scene analysis, spatial sound reproduction by using wave field synthesis, in-car communication, and adaptive signal processing in high-end hearing aids are the topics of this part of the book. All the authors and the editors hope that this book will become a use- ful resource for researchers and developers, as well as for doctoral students, who design new advanced procedures or who are on the “rocky road from algorithms to systems”. It is much more than a pure matter of duty that the editors wish to thank all who helped during the preparation of this book. The dedication of the authors has already been mentioned. Further thanks go to members of the Signal Processing and Signal Theory Group at Darmstadt University of Technology and the Acoustic Signal Processing Group at Harman/Becker AutomotiveSystemsatUlm(Germany)forproofreadingandvariousvaluable hints. Finally, the editors have to thank the Springer Publishing Company, es- pecially Dr. Dietrich Merkle and his colleagues, for their encouragement and their help. Darmstadt and Ulm, Germany Eberhard H¨ansler Gerhard Schmidt Contents Abbreviations and Acronyms ..................................XV Part I Introduction 1 Acoustic Echo and Noise Control – Where did we come from and where are we going? E. Ha¨nsler, G. Schmidt 1.1 The Journey to Maturity..................................... 3 1.2 State of the Art ............................................. 10 1.3 Outline of this Book ......................................... 12 Part II Multi-Microphone Processing 2 Joint Optimization of Acoustic Echo Cancellation and Adaptive Beamforming W. Herbordt, W. Kellermann, S. Nakamura 2.1 Introduction ................................................ 19 2.2 Concepts for Joint Acoustic Echo Cancellation and Adaptive Beamforming ............................................... 21 2.3 Joint Optimization of Acoustic Echo Cancellation and Adaptive Beamforming ............................................... 27 2.4 Implementation ............................................. 34 2.5 Experimental Results ........................................ 38 2.6 Conclusion ................................................. 43 VIII Contents 3 Blind Source Separation of Convolutive Mixtures of Audio Signals in Frequency Domain S. Makino, H. Sawada, R. Mukai, S. Araki 3.1 Introduction ................................................ 51 3.2 Blind Source Separation for Convolutive Mixtures ............... 53 3.3 Overview of Frequency-Domain Approach ...................... 55 3.4 Complex-Valued Independent Component Analysis .............. 58 3.5 Separation Mechanism of Blind Source Separation ............... 60 3.6 Source Localization.......................................... 61 3.7 Permutation Alignment ...................................... 67 3.8 Scaling Alignment ........................................... 72 3.9 Spectral Smoothing.......................................... 72 3.10 Experimental Results ........................................ 75 3.11 Conclusion ................................................. 85 4 Localization and Tracking of Acoustical Sources G. Doblinger 4.1 Introduction ................................................ 91 4.2 Source Localization Using the Generalized Cross-Correlation Function ................................................... 94 4.3 Source Localization Based on Interaural Time Differences ........ 97 4.4 Source Localization Using Adaptive Filters .....................103 4.5 Some Remarks on Algorithm Selection .........................110 4.6 Frequency-Domain Adaptive Beamformer with Speaker Tracking ..111 4.7 Conclusions.................................................120 Part III Echo Cancellation 5 Adaptive Algorithms for the Identification of Sparse Impulse Responses J. Benesty, Y. Huang, J. Chen, P. A. Naylor 5.1 Introduction ................................................125 5.2 Notation and Definitions .....................................126 5.3 Sparseness Measure..........................................128 5.4 The NLMS, PNLMS, and IPNLMS Algorithms..................130 5.5 Universal Criterion ..........................................132 5.6 Exponentiated Gradient Algorithms ...........................135 5.7 The Lambert W Function Based Gradient Algorithm ............140 5.8 Some Important Links Among Algorithms......................141 5.9 Simulations.................................................145 5.10 Conclusions.................................................149 Contents IX 6 Selective-Tap Adaptive Algorithms for Echo Cancellation P. A. Naylor, A. W. H. Khong 6.1 Introduction ................................................156 6.2 Sequential and Periodic Tap Selection..........................157 6.3 MMax Tap Selection.........................................159 6.4 Selective Partial Update Tap Selection .........................166 6.5 Performance Comparison for Single-Channel Selective-Tap algorithms..................................................168 6.6 Convergence Analysis ........................................168 6.7 Sparse Partial Update NLMS .................................179 6.8 multichannel Selective-Tap Algorithms for Stereophonic Acoustic Echo Cancellation ...........................................181 6.9 Exclusive Maximum Tap Selection.............................185 6.10 Exclusive Maximum Adaptive Filters ..........................190 6.11 SAEC Simulation Results ....................................192 6.12 Discussion and Conclusion....................................194 A Appendices .................................................197 7 Nonlinear Acoustic Echo Cancellation F. Ku¨ch, W. Kellermann 7.1 Introduction ................................................205 7.2 Nonlinear Acoustic Echo Paths................................207 7.3 Volterra Filters .............................................211 7.4 Power Filters ...............................................237 7.5 Conclusions.................................................257 8 Intelligent Control Strategies for Hands-Free Telephones C. Breining, A. Mader 8.1 Introduction ................................................263 8.2 Fuzzy Systems ..............................................267 8.3 Learning Vector Quantization.................................276 8.4 Prerequisites for Automatic Optimization of Control Algorithms: Optimum Step Size and Cost Function .........................282 8.5 Radial Basis Function Network for Step-Size Control.............288 8.6 Radial Basis Function Network for State Detection ..............305 Part IV Noise Reduction 9 Noise Reduction U. Heute 9.1 Introduction ................................................325 9.2 Optimum-Filter Design in the Time Domain ....................329 X Contents 9.3 Wiener-Filter Description in the Frequency Domain..............332 9.4 Examples and Filtering Effects................................333 9.5 Wiener-Filter Realizations....................................336 9.6 Spectral Subtraction: Principles and Realization.................339 9.7 Noise Power Density Spectrum Estimation......................343 9.8 Subtraction and Weighting Rules..............................348 9.9 Spectral Analysis and Synthesis ...............................351 9.10 System Configurations, Experiments, and Comparisons...........367 9.11 Further Problems and Ideas, Concluding Remarks ...............376 10 Noise Reduction with Kalman-Filters for Hands-Free Car Phones Based on Parametric Spectral Speech and Noise Estimates H. Puder 10.1 Introduction ................................................385 10.2 Speech and Car Noise Analysis................................387 10.3 Theoretical Basics ...........................................393 10.4 Application of Kalman Filters for Noise Reduction...............404 10.5 Comparison of the Results with Classical Frequency Domain Noise Reduction Approaches..................................420 10.6 Conclusions.................................................425 Part V Selected Applications 11 Evaluation of Algorithms for Speech Enhancement P. Dreiseitel, G. Schmidt 11.1 The Focus of this Chapter....................................431 11.2 Objective Tests for Noise Suppression..........................432 11.3 Comparison Mean Opinion Scores (CMOS) .....................449 11.4 Rhyme Tests................................................468 11.5 Outlook....................................................481 12 An Auditory Scene Analysis Approach to Monaural Speech Segregation G. Hu, D.L. Wang 12.1 Introduction ................................................485 12.2 Computational Auditory Scene Analysis........................488 12.3 Peripheral Analysis and Feature Extraction.....................490 12.4 Auditory Segmentation.......................................497 12.5 Voiced Speech Grouping......................................499 12.6 Unvoiced Speech Grouping ...................................503 12.7 Concluding Remarks.........................................508