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Advanced DSP and Noise reduction P12

IMPULSIVE NOISE 12.1 12.2 12.3 12.4 12.5 12.6 12.7 Impulsive Noise Statistical Models for Impulsive Noise Median Filters Impulsive Noise Removal Using Linear Prediction Models Robust Parameter Estimation Restoration of Archived Gramophone Records Summary I mpulsive noise consists of relatively short duration “on/off” noise pulses, caused by a variety of sources, such as switching noise, adverse channel environments in a communication system, dropouts or surface degradation of audio recordings, clicks from computer keyboards, etc. An impulsive noise filter can be used for enhancing the quality and intelligibility of noisy signals, and for achieving robustness in pattern recognition and adaptive control systems. This chapter. | Advanced Digital Signal Processing and Noise Reduction Second Edition. Saeed V. Vaseghi Copyright 2000 John Wiley Sons Ltd ISBNs 0-471-62692-9 Hardback 0-470-84162-1 Electronic 12 IMPULSIVE NOISE 12.1 Impulsive Noise 12.2 Statistical Models for Impulsive Noise 12.3 Median Filters 12.4 Impulsive Noise Removal Using Linear Prediction Models 12.5 Robust Parameter Estimation 12.6 Restoration of Archived Gramophone Records 12.7 Summary Impulsive noise consists of relatively short duration on off noise pulses caused by a variety of sources such as switching noise adverse channel environments in a communication system dropouts or surface degradation of audio recordings clicks from computer keyboards etc. An impulsive noise filter can be used for enhancing the quality and intelligibility of noisy signals and for achieving robustness in pattern recognition and adaptive control systems. This chapter begins with a study of the frequency time characteristics of impulsive noise and then proceeds to consider several methods for statistical modelling of an impulsive noise process. The classical method for removal of impulsive noise is the median filter. However the median filter often results in some signal degradation. For optimal performance an impulsive noise removal system should utilise a the distinct features of the noise and the signal in the time and or frequency domains b the statistics of the signal and the noise processes and c a model of the physiology of the signal and noise generation. We describe a model-based system that detects each impulsive noise and then proceeds to replace the samples obliterated by an impulse. We also consider some methods for introducing robustness to impulsive noise in parameter estimation. 356 Impulsive Noise 12.1 Impulsive Noise In this section first the mathematical concepts of an analog and a digital impulse are introduced and then the various forms of real impulsive noise in communication systems are considered. The mathematical .