Source: http://www.google.com/patents/US7941315?dq=6,418,462
Timestamp: 2016-12-09 08:50:21
Document Index: 110458791

Matched Legal Cases: ['§119', 'Application No. 2005', 'art 702', 'art 703', 'art 703', 'art 11', 'art 14', 'art 15', 'art 16', 'art 203', 'art 205', 'art 205', 'art 11', 'art 11']

Patent US7941315 - Noise reducer, noise reducing method, and recording medium - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsAccepting the speech having the noise superimposed thereon and converting it into a signal on a time axis of the speech, an amplitude component of a speech for each predetermined frequency band of the converted signal on the frequency axis is calculated. Calculating a noise reduction coefficient, the...http://www.google.com/patents/US7941315?utm_source=gb-gplus-sharePatent US7941315 - Noise reducer, noise reducing method, and recording mediumAdvanced Patent SearchTry the new Google Patents, with machine-classified Google Scholar results, and Japanese and South Korean patents.Publication numberUS7941315 B2Publication typeGrantApplication numberUS 11/385,653Publication dateMay 10, 2011Filing dateMar 22, 2006Priority dateDec 29, 2005Fee statusPaidAlso published asUS20070156399Publication number11385653, 385653, US 7941315 B2, US 7941315B2, US-B2-7941315, US7941315 B2, US7941315B2InventorsNaoshi MatsuoOriginal AssigneeFujitsu LimitedExport CitationBiBTeX, EndNote, RefManPatent Citations (37), Non-Patent Citations (5), Referenced by (13), Classifications (9), Legal Events (2) External Links: USPTO, USPTO Assignment, EspacenetNoise reducer, noise reducing method, and recording medium
US 7941315 B2Abstract
Accepting the speech having the noise superimposed thereon and converting it into a signal on a time axis of the speech, an amplitude component of a speech for each predetermined frequency band of the converted signal on the frequency axis is calculated. Calculating a noise reduction coefficient, the noise component is reduced by multiplying the signal on the frequency axis of the original signal by the calculated noise reduction coefficient. By estimating the target value of the remaining noise for each frequency band, a signal on a frequency axis in which a signal corresponding to a frequency band of which target value estimated by the noise target value is larger than the value of the amplitude component of the signal on the frequency axis of which noise component is reduced is corrected to a signal corresponding to the target value is restored, into a signal on a time axis.
This Nonprovisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2005-380660 filed in Japan on Dec. 29, 2005, the entire contents of which are hereby incorporated by reference.
The signal on the frequency axis that is converted by the signal converting part 702 is multiplied by a coefficient due to the noise reducing part 703. The coefficient of the noise reducing part 703 is a noise reduction coefficient to be described later. For example, in a frequency band only containing a speech, a coefficient is defined as “1” and in the frequency band only containing noise, a coefficient is defined as “0” or a sufficiently small value.
The present invention has been made taking the foregoing problems into consideration and an object of which is to provide a noise reducer, a noise reducing method, and a computer program, which can prevent a speech signal to be outputted from distorted by estimating a target value that reduces the noise on the basis of the speech signal having the inputted noise mixed.
FIG. 1 is a block diagram showing the structure of a computer realizing a noise reducer according to an embodiment of the present invention;
The above-described noise reducer estimates the amplitude component of the noise signal based on the assumption that there is a period of time only having a noise. Accordingly, when one speaker inputs speech, it is necessary for the other speaker to become silent. However, in the usage environment in real, it is difficult to avoid generation of a conversation of a third person as a background noise, so that there is a possibility that the false recognition occurs.
Hereinafter, the present invention will be described with reference to the drawings showing the embodiments thereof. FIG. 1 is a block diagram showing the structure of a computer realizing a noise reducer according to an embodiment of the present invention. The computer according to a noise reducer 1 according to the embodiment of the present invention is at least provided with a calculation processing part 11 such as a CPU and a DSP, a ROM 12, a RAM 13, a communication interface part 14 capable of make the data communication with respect to the outer computer, a speech input part 15 for accepting the input of the speech, and a speech output part 16 for outputting the voice of which noise is reduced.
The noise reducing part 203 multiplies a spectrum IN (x, f) of the inputted speech by a noise reduction coefficient β(f) calculated by the coefficient calculating part 205. Further, the noise reduction coefficient β(f) is a noise reduction coefficient having a value not less than 0 and not more than 1 and it is a coefficient that is obtained for each frequency or for each predetermined frequency band. For example, in the frequency or the frequency band including the speech much, the coefficient is brought close to “1” and in the frequency or the frequency band including a stationary noise such as a background noise is brought close to “0”.
The coefficient calculating part 205 may calculate the noise reduction coefficient β(f) to reduce the noise in units of analysis window x on the basis of the spectrum amplitude |IN (x, f)| of the inputted signal. According to a specific example, after averaging the amplitude spectrum |IN (x, f)| due to a low pass filter or the like, the average value of the spectrum that has been averaged is calculated for each analysis window x to calculate a ratio with respect to the maximum value of the spectrum of the calculated average value. When the calculated rate is 0.5 or more, determining that this analysis window includes the nonstationary noise such as a speech much, the noise reduction coefficient β(f) in this analysis window is brought close to “1”. When the calculated rate is smaller than 0.5, determining that this analysis window includes the stationary noise such as a background noise much, the noise reduction coefficient β(f) in this analysis window is brought close to “0”. It is obvious that the noise reduction coefficient β(f) may be “0” or “1” depending on the state of the background noise.
The calculation processing part 11 of the noise reducer 1 may accept the initial value of the target value (f) at a predetermined frequency of the remaining noise (step S601). The initial value of the accepted target value (f) may be “0” or may be a predetermined constant. The calculation processing part 11 may determine if the value of the amplitude component (f) at a predetermined frequency f that is Fourier-transformed at a predetermined analysis window is larger than the target value (f) or not (step S602).
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