Acoustic Echo and Noise Control

EBERHARD HANSLER, Dr.--Ing., is Professor of Electrical Engineering at the Darmstadt University of Technology, Darmstadt, Germany. GERHARD SCHMIDT, Dr.--Ing., is a Research Engineer at Temic Speech Dialog Systems in Ulm, Germany.

List of Figures. List of Tables. Preface. Acknowledgments. Abbreviations and Acronyms. Part I: Basics. 1 Introduction. 1.1 Some History. 1.2 Overview of the Book. 2 Acoustic Echo and Noise Control Systems. 2.1 Notation. 2.2 Applications. 3 Fundamentals. 3.1 Signals. 3.2 Acoustic Echoes. 3.3 Standards. Part II: Algorithms. 4 Error Criteria and Cost Functions. 4.1 Error Criteria for Adaptive Filters. 4.2 Error Criteria for Filter Design. 4.3 Error Criteria for Speech Processing and Control Purposes. 5 Wiener Filter. 5.1 Time--Domain Solution. 5.2 Frequency--Domain Solution. 6 Linear Prediction. 6.1 Normal Equations. 6.2 Levinson{Durbin Recursion. 7 Algorithms for Adaptive Filters. 7.1 The Normalized Least Mean Square Algorithm. 7.2 The Affine Projection Algorithm. 7.3 The Recursive Least Squares Algorithm. 7.4 The Kalman Algorithm. Part III: Acoustic Echo and Noise Control. 8 Traditional Methods for Stabilization of Electroacoustic Loops. 8.1 Adaptive Line Enhancement. 8.2 Frequency Shift. 8.3 Controlled Attenuation. 9 Echo Cancellation. 9.1 Processing Structures. 9.2 Stereophonic and Multichannel Echo Cancellation. 10 Residual Echo and Noise Suppression. 10.1 Basics. 10.2 Suppression of Residual Echoes. 10.3 Suppression of Background Noise. 10.4 Combining Background Noise and Residual Echo Suppression. 11 Beamforming. 11.1 Basics. 11.2 Characteristics of Microphone Arrays. 11.3 Fixed Beamforming. 11.4 Adaptive Beamforming. Part IV: Control and Implementation Issues. 12 System Control Basic Aspects. 12.1 Convergence versus Divergence Speed. 12.2 System Levels for Control Design. 13 Control of Echo Cancellation Systems. 13.1 Pseudooptimal Control Parameters for the NLMS Algorithm. 13.2 Pseudooptimal Control Parameters for the Affine Projection Algorithm. 13.3 Summary of Pseudooptimal Control Parameters. 13.4 Detection and Estimation Methods. 13.5 Detector Overview and Combined Control Methods. 14 Control of Noise and Echo Suppression Systems. 14.1 Estimation of Spectral Power Density of Background Noise. 14.2 Musical Noise. 14.3 Control of Filter Characteristics. 15 Control for Beamforming. 15.1 Practical Problems. 15.2 Stepsize Control. 16 Implementation Issues. 16.1 Quantization Errors. 16.2 Number Representation Errors. 16.3 Arithmetical Errors. 16.4 Fixed Point versus Floating Point. 16.5 Quantization of Filter Taps. Part V: Outlook and Appendixes. 17 Outlook. Appendix A: Subband Impulse Responses. A.1 Consequences for Subband Echo Cancellation. A.2 Transformation. A.3 Concluding Remarks. Appendix B: Filterbank Design. B.1 Conditions for Approximately Perfect Reconstruction. B.2 Filter Design Using a Product Approach. B.3 Design of Prototype Lowpass Filters. B.4 Analysis of Prototype Filters and the Filterbank System. References. Index.