Sub-band exponential smoothing noise canceling system
DC CAFCFirst Claim
1. An apparatus for canceling noise by time domain processing sub-bands of a digital input signal, comprising:
- input means for inputting a digital input signal which includes a noise signal;
band splitting means for dividing said digital input signal into a plurality of frequency-limited time-domain signal sub-bands by using single side band modulation and a DFT filter bank;
a plurality of noise processing means each for processing a corresponding one of said plurality of signal sub-bands such that said noise signal included in said digital input signal is cancelled;
wherein each noise processing means is further comprised of exponential averaging means, noise estimating means, and subtraction processing means; and
recombining means for recombining the noise processed plurality of signal sub-bands into a digital output signal.
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Abstract
A noise canceling method and apparatus for canceling noise by time domain processing sub-bands of a digital input signal. The input signal is divided into a number of frequency-limited time-domain sub-bands. Each sub-band is then individually processed to cancel noise present in the signal. The noise processing includes exponential averaging of the input, noise estimation, and subtraction processing. The noise subtraction process is simplified by generating a filter coefficient that is exponentially smoothed, hard limited, and multiplied with the input signal to generate the noise processed output for each sub-band. The noise processed bands are then recombined into a digital output signal. Implementation may be effected in software or hardware and applied to various noise canceling and signal processing applications.
67 Citations
14 Claims
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1. An apparatus for canceling noise by time domain processing sub-bands of a digital input signal, comprising:
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input means for inputting a digital input signal which includes a noise signal;
band splitting means for dividing said digital input signal into a plurality of frequency-limited time-domain signal sub-bands by using single side band modulation and a DFT filter bank;
a plurality of noise processing means each for processing a corresponding one of said plurality of signal sub-bands such that said noise signal included in said digital input signal is cancelled;
wherein each noise processing means is further comprised of exponential averaging means, noise estimating means, and subtraction processing means; and
recombining means for recombining the noise processed plurality of signal sub-bands into a digital output signal. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for canceling noise by time domain processing sub-bands of a digital input signal, comprising the steps of:
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inputting a digital input signal which includes a noise signal;
dividing said digital input signal into a plurality of sub-bands by using single side band modulation and a DFT filter bank;
noise processing a corresponding one of said plurality of sub-bands such that said noise signal included in said digital input signal is canceled;
said noise processing step further comprising the steps of exponential averaging, noise estimating, and subtraction processing; and
recombining the noise processed plurality of sub-bands into a digital output signal using a recombining means. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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Specification