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Patent No. 6249749  Method and apparatus for separation of impulsive and non-impulsive components in a signal (Tran, et al., Jun 19, 2001)

Abstract

Impulsive components and non-impulsive components within any time-domain signal such as audio, video, vibration, etc., are separated using wavelet analysis and sorting of wavelet coefficient sets according to statistical parameters of each respective coefficient set. Each entire coefficient set is either included or excluded from each respective separated component based on the statistical parameter. Thus, automatic, adaptive, flexible, and reliable separation of impulsive and non-impulsive components is achieved.

Notes:

SUMMARY OF THE INVENTION

The present invention has the advantage of accurately separating impulsive and non-impulsive signal components in an adaptive and efficient manner.

In one aspect of the invention, a method of separating impulsive and non-impulsive signal components in a time-domain signal is comprised of decomposing the time-domain signal using a wavelet transform to produce a plurality of sets of wavelet coefficients. Each set of wavelet coefficients corresponds to a respective time-versus-frequency span. A respective statistical parameter is determined for each set of wavelet coefficients. A new time-domain signal is re-synthesized using an inverse wavelet transform applied to selected ones of the sets of wavelet coefficients. The selected ones are selected in response to the respective statistical parameters.

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Based on the foregoing, the present invention automatically detects and separates impulsive signal components (such as static noises in communication signals or road-induced squeaks and rattles in automobiles) from non-impulsive components (such as background noise) for any types of signals using a predetermined threshold. The invention is adaptive to different types of signals and threshold levels. The invention achieves fast processing speed and may be implemented using general or customized integrated circuits. The invention may be used to identify and separate out impulsive noise signatures reflecting abnormalities of machine operations (e.g., bearing failure, quality control issues, etc.). The invention is also useful in communication, medical imaging and other applications where other impulsive noises or information need to be separated such as in the isolation of static noises, extraneous noises, vibrations or disturbances, and others.