Understanding Active Noise Cancellation (Hardcover)

Contents:
Chapter One. A Little History. 1.1 Introduction. 1.2 Early history. 1.3 Later history 1.4 The future. Chapter Two: Foundations of Active Control. 2.1 Physical mechanisms 2.2 Basic structure of active noise Control systems. 2.3. Control system optimisation. 2.3.1 Influence of control source output power and placement. 2.3.2 Influence of error sensor placement. 2.3.3 Influence of reference signal delay and quality. Chapter Three: The Electronic Control System. 3.1 Introduction 3.2 Control Filter. 3.3 Cancellation path transfer function estimation. 3.4 Adaptation algorithms. 3.4.1 FXLMS algorithm for adapting the weights of an FIR filter. 3.4.2 Multi-channel and filtered-U RLS algorithms for IIR filters. 3.4.3 Genetic algorithms. 3.4.3.1 Killing selection instead of survivor selection. 3.4.3.2 Weight String Instead of Binary Encoding. 3.4.3.3 Mutation probability and amplitude 3.4.3.4 Rank-based selection 3.4.3.5 Uniform crossover 3.4.3.6 Genetic algorithm parameter adjustment 3.4.3.7 Performance measurement 3.5 Putting it all together 3.6 Important practical controller implementation issues 3.6.1 Microprocessor selection. 3.6.2 Converter type and group delay considerations 3.6.3 Digital sampling rate 3.6.4 Algorithm considerations 3.6.5 Accuracy of controller output. Chapter Four: Active Noise Control Sources. 4.1 Acoustic sources. 4.2 Vibration sources. Chapter Five: Error Sensors. 5.1 Microphones. 5.2 Vibration sensing and control of sound radiation 5.3 Sound intensity and energy density control. 5.4 Control algorithms for various sensing strategies. 5.4.1 Shaped or distributed structural sensors. 5.4.2. Sound intensity 5.4.3 Energy density. 5.4.4 Power or intensity squared. Chapter Six: Applications of Active Noise Control. 6.1 Some general considerations. 6.2 Application Examples. 6.2.1 Sound propagation in ducts. 6.2.2.1 Plane wave propagation 6.2.2.2 Higher order mode propagation 6.2.3 Sound radiation from vibrating structures 6.2.3.1 Physical control mechanisms 6.2.3.2 Control actuators and error sensors. 6.2.4 Active headsets and ear muffs. 6.2.4.1 Feedback systems 6.2.4.2 Feedforward systems 6.2.4.2 Transducer considerations 6.2.4.3 Transducer considerations 6.2.5 Sound transmission into enclosed spaces 6.2.5.1 Global reduction of low frequency tonal noise in propellor aircraft 6.2.5.2 Reduction of interior noise in diesel engine-driven, mobile mining equipment 6.2.5.3 Local reduction of broadband noise in large aircraft 6.2.5.4 Global reduction of low frequency road noise in cars 6.2.6 Active vibration isolation. 6.3 Examples of applications which are impractical. 6.3.1 Global reduction of broadband or high frequency tonal noise in large aircraft 6.3.2 Global reduction of broadband or transient noise transmitted into a building space. 6.3.3 Reduction of traffic or aircraft flyover noise transmitted into a building. 6.3.4 Global reduction of tonal or periodic noise in a large space such as a factory which contains many noise sources. 6.3.5 Global reduction of broadband in a large factory 6.3.6 Reduction of broadband noise outdoors 6.3.7 Reduction of transient noise outdoors. Chapter Seven: Current and Future Directions. 7.1 Commercial control system requirements 7.1.1 Controller hardware 7.1.2 Controller software 7.2 Acoustic system software 7.3 Current research directions 7.3.1 Sound sources 7.3.2 Error sensors 7.3.3 Optimisation of control source and error sensor locations 7.3.4 Control filters and algorithms 7.3.5 Coupled systems 7.3.6 Hybrid active/passive silencers. 7.4 Summary. References. Useful web-sites for more information.