Noise suppression based on bark band wiener filtering and modified doblinger noise estimate
First Claim
1. In a noise suppression circuit including a circuit for calculating a noise estimate, a circuit for subtracting the noise estimate from an input signal, and a synthesis circuit for combining frames into an output signal, the improvement comprising:
- a plurality of band pass filters for dividing an input signal into a plurality of bands;
means for detecting speech in each band;
an analysis circuit for dividing the signal from each filter into a plurality of frames with each frame containing a plurality of samples;
means for calculating a noise suppression factor inversely proportional to the signal to noise ratio of each frame in each band.
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Accused Products
Abstract
In a noise suppresser, an input signal is converted to frequency domain by discrete Fourier analysis and divided into Bark bands. Noise is estimated for each band. The circuit for estimating noise includes a smoothing filter having a slower time constant for updating the noise estimate during noise than during speech. The noise suppresser further includes a circuit to adjust a noise suppression factor inversely proportional to the signal to noise ratio of each frame of the input signal. A noise estimate is subtracted from the signal in each band. A discrete inverse Fourier transform converts the signals back to the time domain and overlapping and combined windows eliminate artifacts that may have been produced during processing.
40 Citations
15 Claims
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1. In a noise suppression circuit including a circuit for calculating a noise estimate, a circuit for subtracting the noise estimate from an input signal, and a synthesis circuit for combining frames into an output signal, the improvement comprising:
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a plurality of band pass filters for dividing an input signal into a plurality of bands; means for detecting speech in each band; an analysis circuit for dividing the signal from each filter into a plurality of frames with each frame containing a plurality of samples; means for calculating a noise suppression factor inversely proportional to the signal to noise ratio of each frame in each band. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 14)
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9. In a noise suppression circuit including an analysis circuit for dividing an input signal into a plurality of frames, each frame containing a plurality of samples, a circuit for calculating a noise estimate, a circuit for subtracting the noise estimate from the input signal, and a synthesis circuit for reconstructing the frames into an output signal, the improvement comprising:
a smoothing filter in said circuit for calculating a noise estimate, said smoothing filter having a time constant for updating the noise estimate of a frame, wherein said time constant increases when a noisy speech spectrum deviates from a noise estimate by more than a predetermined amount and said time constant decreases when the noisy speech spectrum deviates from the noise estimate by less than the predetermined amount, thereby slowing the change in estimate from frame to frame when a noisy speech spectrum deviates from a noise estimate by more than a predetermined amount. - View Dependent Claims (10, 11, 12, 13, 15)
Specification