System, method and apparatus for cancelling noise
DC CAFCFirst Claim
1. An apparatus for canceling noise, comprising:
- an input for inputting an audio signal which includes a noise signal;
a frequency spectrum generator for generating the frequency spectrum of said audio signal thereby generating frequency bins of said audio signal; and
a threshold detector for setting a threshold for each frequency bin using a noise estimation process and for detecting for each frequency bin whether the magnitude of the frequency bin is less than the corresponding threshold, thereby detecting the position of noise elements for each frequency bin.
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Accused Products
Abstract
A threshold detector precisely detects the positions of the noise elements, even within continuous speech segments, by determining whether frequency spectrum elements, or bins, of the input signal are within a threshold set according to current and future minimum values of the frequency spectrum elements. In addition, the threshold is continuously set and initiated within a predetermined period of time. The estimate magnitude of the input audio signal is obtained using a multiplying combination of the real and imaginary part of the input in accordance with the higher and lower values between the real and imaginary part of the signal. In order to further reduce instability of the spectral estimation, a two-dimensional smoothing is applied to the signal estimate using neighboring frequency bins and an exponential average over time. A filter multiplication effects the subtraction thereby avoiding phase calculation difficulties and effecting full-wave rectification which further reduces artifacts. Since the noise elements are determined within continuous speech segments, the noise is canceled from the audio signal nearly continuously thereby providing excellent noise cancellation characteristics. Residual noise reduction reduces the residual noise remaining after noise cancellation. Implementation may be effected in various noise canceling schemes including adaptive beamforming and noise cancellation using computer program applications installed as software or hardware.
346 Citations
47 Claims
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1. An apparatus for canceling noise, comprising:
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an input for inputting an audio signal which includes a noise signal;
a frequency spectrum generator for generating the frequency spectrum of said audio signal thereby generating frequency bins of said audio signal; and
a threshold detector for setting a threshold for each frequency bin using a noise estimation process and for detecting for each frequency bin whether the magnitude of the frequency bin is less than the corresponding threshold, thereby detecting the position of noise elements for each frequency bin. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. An apparatus for canceling noise, comprising:
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input means for inputting an audio signal which includes a noise signal;
frequency spectrum generating means for generating the frequency spectrum of said audio signal thereby generating frequency bins of said audio signal; and
threshold detecting means for setting a threshold for each frequency bin using a noise estimation process and for detecting for each frequency bin whether the magnitude of the frequency bin is less than the corresponding threshold, thereby detecting the position of noise elements for each frequency bin. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37)
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38. A method for driving a computer processor for generating a noise canceling signal for canceling noise from an audio signal representing audible sound including a noise signal representing audible noise, said method comprising the steps of:
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inputting said audio signal which includes said noise signal;
generating the frequency spectrum of said audio signal thereby generating frequency bins of said audio signal;
setting a threshold for each frequency bin using a noise estimation process;
detecting for each frequency bin whether the magnitude of the frequency bin is less than the corresponding threshold, thereby detecting the position of noise elements for each frequency bin; and
subtracting said noise elements detected in said step of detecting from said audio signal to produce an audio signal representing said audible sound substantially without said audible noise. - View Dependent Claims (39, 40, 41, 42, 43, 44, 45, 46, 47)
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Specification