| Abbreviations and Acronyms | p. 1 |
| Introduction | |
| Overview about the Book | p. 8 |
| Speech Enhancement | |
| Low Delay Filter-Banks for Speech and Audio Processing | |
| Introduction | p. 13 |
| Analysis-Synthesis Filter-Banks | p. 15 |
| General Structure | p. 15 |
| Tree-Structured Filter-Banks | p. 16 |
| Modulated Filter-Banks | p. 17 |
| Frequency Warped Filter-Banks | p. 20 |
| Low Delay Filter-Banks | p. 26 |
| The Filter-Bank Equalizer | p. 29 |
| Concept | p. 29 |
| Prototype Filter Design | p. 31 |
| Relation between GDFT and GDCT | p. 33 |
| Realization for Different Filter Structures | p. 35 |
| Polyphase Network Implementation | p. 37 |
| The Non-Uniform Filter-Bank Equalizer | p. 41 |
| Comparison between FBE and AS FB | p. 43 |
| Algorithmic Complexity | p. 43 |
| Further Measures for Signal Delay Reduction | p. 44 |
| Concept | p. 45 |
| Approximation by a Moving-Average Filter | p. 45 |
| Approximation by an Auto-Regressive Filter | p. 46 |
| Algorithmic Complexity | p. 47 |
| Warped Filter Approximation | p. 48 |
| Application to Noise Reduction | p. 49 |
| System Configurations | p. 49 |
| Instrumental Quality Measures | p. 50 |
| Simulation Results for the Uniform Filter-Banks | p. 51 |
| Simulation Results for the Warped Filter-Banks | p. 53 |
| Conclusions | p. 55 |
| References | p. 56 |
| A Pre-Filter for Hands-Free Car Phone Noise Reduction: Suppression of Harmonic Engine Noise Components | |
| Introduction | p. 63 |
| Analysis of the Different Car Noise Components | p. 64 |
| Wind Noise | p. 65 |
| Tire Noise | p. 65 |
| Engine Noise | p. 66 |
| Engine Noise Removal Based on Notch Filters | p. 68 |
| Compensation of Engine Harmonics with Adaptive Filters | p. 73 |
| Step-Size Control | p. 75 |
| Calculating the Optimal Step-Size | p. 78 |
| Results of the Compensation Approach | p. 80 |
| Evaluation and Comparison of the Results Obtained by the Notch Filter and the Compensation Approach | p. 84 |
| Conclusions and Summary | p. 85 |
| Conclusion | p. 85 |
| Summary | p. 86 |
| References | p. 87 |
| Model-Based Speech Enhancement | |
| Introduction | p. 89 |
| Conventional Speech Enhancement Schemes | p. 91 |
| Speech Enhancement Schemes Based on Nonlinearities | p. 93 |
| Speech Enhancement Schemes Based on Speech Reconstruction | p. 97 |
| Feature Extraction and Control | p. 99 |
| Reconstruction of Speech Signals | p. 110 |
| Combining the Reconstructed and the Noise Suppressed Signal | p. 124 |
| Adding the Fully Reconstructed Signal | p. 125 |
| Adding only the Voiced Part of the Reconstructed Signal | p. 129 |
| Summary and Outlook | p. 133 |
| References | p. 133 |
| Bandwidth Extension of Telephony Speech | |
| Introduction | p. 135 |
| Organization of the Chapter 137 | |
| Basics | p. 138 |
| Human Speech Generation | p. 139 |
| Source-Filter Model | p. 141 |
| Parametric Representations of the Spectral Envelope | p. 143 |
| Distance Measures | p. 147 |
| Non-Model-Based Algorithms for Bandwidth Extension | p. 149 |
| Oversampling with Imaging | p. 149 |
| Spectral Shifting | p. 151 |
| Application of Non-Linear Characteristics | p. 153 |
| Model-Based Algorithms for Bandwidth Extension | p. 153 |
| Generation of the Excitation Signal | p. 155 |
| Vocal Tract Transfer Function Estimation | p. 159 |
| Evaluation of Bandwidth Extension Algorithms | p. 176 |
| Objective Distance Measures | p. 177 |
| Subjective Measures | p. 180 |
| Conclusions | p. 181 |
| References | p. 182 |
| Dereverberation and Residual Echo Suppression in Noisy Environments | |
| Introduction | p. 186 |
| Problem Formulation | p. 188 |
| OM-LSA Estimator for Multiple Interferences | p. 191 |
| OM-LSA Estimator | p. 191 |
| A priori SIR Estimator | p. 193 |
| Dereverberation of Noisy Speech Signals | p. 195 |
| Short Introduction to Speech Dereverberation | p. 195 |
| Problem Formulation | p. 197 |
| Statistical Reverberation Model | p. 199 |
| Late Reverberant Spectral Variance Estimator | p. 200 |
| Summary and Discussion | p. 203 |
| Residual Echo Suppression | p. 203 |
| Problem Formulation | p. 204 |
| Late Residual Echo Spectral Variance Estimator | p. 206 |
| Parameter Estimation | p. 208 |
| Summary | p. 210 |
| Joint Suppression of Reverberation, Residual Echo, and Noise | p. 210 |
| Experimental Results | p. 212 |
| Experimental Setup | p. 214 |
| Joint Suppression of Reverberation and Noise | p. 214 |
| Suppression of Residual Echo | p. 216 |
| Joint Suppression of Reverberation, Residual Echo, and Noise | p. 221 |
| Summary and Outlook | p. 223 |
| References | p. 224 |
| Low Distortion Noise Cancellers — Revival of a Classical Technique | |
| Introduction | p. 229 |
| Distortions in Widrow's Adaptive Noise Canceller | p. 230 |
| Distortion by Interference | p. 230 |
| Distortion by Crosstalk | p. 232 |
| Paired Filter (PF) Structure | p. 233 |
| Algorithm | p. 233 |
| Evaluations | p. 235 |
| Crosstalk Resistant ANC and Cross-Coupled Structure | p. 239 |
| Crosstalk Resistant ANC | p. 240 |
| Cross-Coupled Structure | p. 241 |
| Cross-Coupled Paired Filter (CCPF) Structure | p. 242 |
| Algorithm | p. 242 |
| Evaluations | p. 245 |
| Generalized Cross-Coupled Paired Filter (GCCPF) Structure | p. 247 |
| Algorithm | p. 250 |
| Evaluation by Recorded Signals | p. 251 |
| Demonstration in a Personal Robot | p. 261 |
| Conclusions | p. 261 |
| References | p. 263 |
| Echo Cancellation | |
| Nonlinear Echo Cancellation Based on Spectral Shaping | |
| Introduction | p. 267 |
| Frequency-Domain Model of Highly Nonlinear Residual Echo | p. 268 |
| Spectral Correlation Between Residual Echo and Echo Replica | p. 269 |
| Model of Residual Echo Based on Spectral Correlation | p. 273 |
| Echo Canceller Based on the New Residual Echo Model | p. 274 |
| Overall Structure | p. 274 |
| Estimation of Near-End Speech | p. 275 |
| Spectral Gain Control | p. 276 |
| Evaluations | p. 277 |
| Objective Evaluations | p. 277 |
| Subjective Evaluation | p. 279 |
| DSP Implementation and Real-Time Evaluation | p. 280 |
| Conclusions | p. 280 |
| References | p. 281 |
| Signal and System Quality Evaluation | |
| Telephone-Speech Quality | |
| Telephone-Speech Signals | p. 287 |
| Telephone Scenario | p. 287 |
| Telephone-Scenario Model | p. 287 |
| Speech-Signal Quality | p. 289 |
| Intelligibility | p. 289 |
| Speech-Sound Quality | p. 290 |
| Speech-Quality Assessment | p. 292 |
| Auditory Quality Assessment | p. 292 |
| Aims | p. 292 |
| Instrumental Quality Assessment | p. 293 |
| Compound-System Quality Prediction | p. 293 |
| The System-Planning Task | p. 293 |
| ETSI Network-Planning Model (E-Model) | p. 293 |
| Auditory Total-Quality Assessment | p. 294 |
| Conversation Tests | p. 294 |
| Listening Tests | p. 296 |
| LOTs with Pair Comparisons | p. 296 |
| Absolute-Category Rating (ACR) LOTs | p. 297 |
| Auditory Quality-Attribute Analysis | p. 298 |
| Quality Attributes | p. 298 |
| Attribute-Oriented LOTs | p. 298 |
| Search for Suitable Attributes | p. 302 |
| Integral-Quality Estimation from Attributes | p. 305 |
| Instrumental Total-Quality Measurement | p. 306 |
| Signal Comparisons | p. 306 |
| Evaluation Approaches | p. 306 |
| Psychoacoustically Motivated Measures | p. 312 |
| Instrumental Attribute-Based Quality Measurements | p. 320 |
| Basic Ideas | p. 320 |
| Loudness | p. 322 |
| Sharpness | p. 323 |
| Roughness | p. 323 |
| Directness/Frequency Content (DFC) | p. 324 |
| Continuity | p. 326 |
| Noisiness | p. 329 |
| Combined Direct and Attribute-Based Total Quality Determination | p. 331 |
| Conclusions, Outlook, and Final Remarks | p. 331 |
| References | p. 332 |
| Evaluation of Hands-free Terminals | |
| Introduction | p. 339 |
| Quality Assessment of Hands-free Terminals | p. 340 |
| Subjective Methods for Determining the Communicational Quality | p. 342 |
| General Setup and Opinion Scales Used for Subjective Performance Evaluation | p. 343 |
| Conversation Tests | p. 345 |
| Double Talk Tests | p. 346 |
| Talking and Listening Tests | p. 347 |
| Listening-only Tests (LOT) and Third Party Listening Tests | p. 348 |
| Experts Tests for Assessing Real Life Situations | p. 349 |
| Test Environment | p. 350 |
| The Acoustical Environment | p. 351 |
| Background Noise Simulation Techniques | p. 351 |
| Positioning of the Hands-Free Terminal | p. 352 |
| Positioning of the Artificial Head | p. 352 |
| Influence of the Transmission System | p. 354 |
| Test Signals and Analysis Methods | p. 354 |
| Speech and Perceptual Speech Quality Measures | p. 356 |
| Speech-like Test Signals | p. 356 |
| Background Noise | p. 360 |
| Applications | p. 363 |
| Result Representation | p. 365 |
| Interpretation of HFT "Quality Pies" | p. 366 |
| Examples | p. 368 |
| Related Aspects | p. 368 |
| The Lombard Effect | p. 368 |
| Intelligibility Outside Vehicles | p. 372 |
| References | p. 375 |
| Multi-Channel Processing | |
| Correlation-Based TDOA-Estimation for Multiple Sources in Reverberant Environments | |
| Introduction | p. 381 |
| Analysis of TDOA Ambiguities | p. 383 |
| Signal Model | p. 383 |
| Multipath Ambiguity | p. 384 |
| Multiple Source Ambiguity | p. 384 |
| Ambiguity due to Periodic Signals | p. 386 |
| Principles of TDOA Disambiguation | p. 386 |
| Estimation of Direct Path TDOAs | p. 390 |
| Correlation and Extremum Positions | p. 390 |
| Raster Matching | p. 392 |
| Consistent TDOA Graphs | p. 397 |
| TDOA Graph | p. 397 |
| Strategies of Consistency Check | p. 398 |
| Properties of TDOA Graphs | p. 399 |
| Efficient Synthesis Algorithm | p. 402 |
| Initialization and Termination | p. 404 |
| Estimating the Number of Active Sources | p. 405 |
| Experimental Results | p. 406 |
| Localization System | p. 406 |
| TDOA Estimation of a Single Signal Block | p. 408 |
| Source Position Estimation | p. 412 |
| Evaluation of Continuous Measurements | p. 412 |
| Summary | p. 414 |
| References | p. 415 |
| Microphone Calibration for Multi-Channel Signal Processing | |
| Introduction | p. 417 |
| Beamforming with Ideal Microphones | p. 418 |
| Principle of Beamforming | p. 418 |
| Evaluation of Beamformers | p. 421 |
| Statistically Optimum Beamformers | p. 424 |
| Microphone Mismatch and its Effect on Beamforming | p. 427 |
| Model for Non-Ideal Microphone Characteristics | p. 428 |
| Effect of Microphone Mismatch on Fixed Beamformers | p. 429 |
| Effect of Microphone Mismatch on Adaptive Beamformers | p. 430 |
| Comparison of Fixed and Adaptive Beamformers | p. 432 |
| Calibration Techniques and their Limits for Real-World Applications | p. 432 |
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