CN106328160B - Noise reduction method based on double microphones - Google Patents

Noise reduction method based on double microphones Download PDF

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CN106328160B
CN106328160B CN201510355966.1A CN201510355966A CN106328160B CN 106328160 B CN106328160 B CN 106328160B CN 201510355966 A CN201510355966 A CN 201510355966A CN 106328160 B CN106328160 B CN 106328160B
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power spectrum
noise
frame signal
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CN106328160A (en
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羊开云
高可攀
韩翀蛟
徐晓峰
李夏宾
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GRANDSTREAM NETWORK Inc
SHENZHEN GRANDSTREAM NETWORKS Inc
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SHENZHEN GRANDSTREAM NETWORKS Inc
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Abstract

The invention provides a noise reduction method based on double microphones, which comprises the following steps: step a: the method comprises the steps that a first channel collects a first voice signal containing noise from a first microphone, a second channel collects a second voice signal containing noise from a second microphone, and framing processing is respectively carried out on the first voice signal and the second voice signal after sampling to obtain a first channel frame signal and a second channel frame signal; step b: calculating the module value of the coherence coefficient of the first channel frame signal and the second channel frame signal
Figure 468548DEST_PATH_IMAGE001
(ii) a Step c: respectively calculating the power spectrum of the frame signal, and respectively predicting the noise power spectrum; step d: and calculating a predicted signal power spectrum, calculating the adjustment gain of each frequency line of the first channel frame signal and the second channel frame signal by combining the predicted signal power spectrum and the noise power spectrum, and finally realizing the self-adaptive filtering of the first channel frame signal and the second channel frame signal. The technical scheme of the invention improves the accuracy of prediction and has good effect of inhibiting background noise.

Description

Noise reduction method based on double microphones
Technical Field
The invention belongs to the field of communication, and particularly relates to a double-microphone noise reduction technology based on mobile communication equipment.
Background
In recent years, the occurrence of VoIP technology enables voice communication to be lower in cost and more convenient and faster in communication. With the development of the voice call technology, the VoIP terminal is frequently used in daily life and work communication. People have higher and higher requirements on the quality of VoIP voice calls, and voice signals need to restore the authenticity of voices of speakers as much as possible while noise is reduced as much as possible. When the VoIP terminal is used in some important working conferences, the requirements of users on noise reduction techniques are more severe, and it is necessary to control noise to be out of the hearing range of human ears as much as possible while ensuring the voice hearing feeling, and to still ensure the call quality under the condition of a certain distance from the call terminal.
The existing voice noise reduction technology mainly comprises a spectral subtraction method and an adaptive noise reduction technology. However, both methods have certain limitations, and the spectral subtraction method has poor tracking effect on noise and cannot eliminate background noise. Most of the existing adaptive noise elimination technologies adopt fixed parameters to predict the power spectrum of a signal, so that an adaptive noise elimination filter is obtained to achieve the effect of noise elimination. The method is lack of tracking real-time performance for noise and voice, the voice is easy to distort under the condition of large noise suppression, and the noise is large and interferes the voice content to cause unclear voice when the voice quality is good. Therefore, how to predict the signal power spectrum more flexibly so as to distinguish the noise power spectrum from the voice power spectrum, and performing adaptive filtering on the voice signal by using the prediction result is the challenge and key of the noise reduction technology of the VoIP terminal.
Disclosure of Invention
The invention aims to provide a noise reduction method based on double microphones, which can eliminate the built-in noise generated by heat dissipation in the running process of a VoIP terminal and has good inhibition effect on background noise.
A noise reduction method based on double microphones mainly comprises the following steps:
step a: the method comprises the steps that a first channel collects a first voice signal containing noise from a first microphone, a second channel collects a second voice signal containing noise from a second microphone, and framing processing is respectively carried out on the first voice signal and the second voice signal after sampling to obtain a first channel frame signal and a second channel frame signal;
step b: calculating the module value of the coherence coefficient of the first channel frame signal and the second channel frame signal
Figure 590588DEST_PATH_IMAGE001
Step c: respectively calculating the power spectrum of the frame signal according to the first channel frame signal and the second channel frame signal, and respectively predicting the noise power spectrum;
step d: according to the predicted signal-to-noise ratio and the module value of the coherence coefficient
Figure 694679DEST_PATH_IMAGE001
And calculating the power spectrum of the predicted signal according to the power spectrum of the current frame signal and the power spectrum of the noise of the previous frame, calculating the gain of each frequency line of the first channel frame signal and the second channel frame signal by combining the power spectrum of the predicted signal and the power spectrum of the noise, and finally realizing the self-adaptive filtering of the first channel frame signal and the second channel frame signal.
Preferably, in the noise reduction method based on dual microphones of the present invention, the module value of the coherence coefficient is
Figure 412099DEST_PATH_IMAGE001
Comprises the following steps:
Figure 994259DEST_PATH_IMAGE002
wherein
Figure 870948DEST_PATH_IMAGE003
and
Figure 4995DEST_PATH_IMAGE004
the calculation formula is as follows for the mean values of the discrete time domain frame signals of the first channel and the second channel respectively:
Figure 209712DEST_PATH_IMAGE005
Figure 595562DEST_PATH_IMAGE006
the first sampling point signal in the first channel frame signal is recorded as
Figure 326758DEST_PATH_IMAGE007
In the second channel frame signal
Figure 507073DEST_PATH_IMAGE008
A sampling point signal is recorded as
Figure 199085DEST_PATH_IMAGE009
Preferably, in the dual-microphone based noise reduction method, the power spectrums of the frame signals of the first channel and the second channel are respectively recorded as:
Figure 123048DEST_PATH_IMAGE010
Figure 584116DEST_PATH_IMAGE011
first channel frame signal
Figure 325545DEST_PATH_IMAGE012
A spectral coefficient is recorded as
Figure 691804DEST_PATH_IMAGE013
Second channel frame signal
Figure 91561DEST_PATH_IMAGE012
A spectral coefficient is recorded as
Figure 108934DEST_PATH_IMAGE014
The formula of the frame signal power spectrum is as follows:
Figure 529854DEST_PATH_IMAGE015
Figure 570360DEST_PATH_IMAGE016
preferably, in the dual-microphone based noise reduction method, the current frame noise power spectrums of the first channel frame signal and the second channel frame signal are respectively recorded as
Figure 773809DEST_PATH_IMAGE017
Figure 521054DEST_PATH_IMAGE018
Figure 355018DEST_PATH_IMAGE019
The power spectrum of the noise of the previous frame of the first channel frame signal and the second channel frame signal is recorded as
Figure 866508DEST_PATH_IMAGE020
Figure 686697DEST_PATH_IMAGE021
Figure 413082DEST_PATH_IMAGE022
The calculation formula is as follows:
Figure 854165DEST_PATH_IMAGE023
Figure 416734DEST_PATH_IMAGE024
preferably, in the dual-microphone based noise reduction method, the calculation formula of the predicted signal power spectrum is as follows:
Figure 148935DEST_PATH_IMAGE025
Figure 746139DEST_PATH_IMAGE026
Figure 859588DEST_PATH_IMAGE027
wherein
Figure 722502DEST_PATH_IMAGE028
and
Figure 507662DEST_PATH_IMAGE029
the power spectrum of the self-signal of the previous frame of the first channel and the second channel respectively is adapted with a prediction coefficient of
Figure 506842DEST_PATH_IMAGE030
Figure 978143DEST_PATH_IMAGE031
The predicted signal-to-noise ratio is:
Figure 328353DEST_PATH_IMAGE032
Figure 480986DEST_PATH_IMAGE031
preferably, in the dual-microphone based noise reduction method, the frequency domain adjustment gains of the first channel frame signal and the second channel frame signal are calculated by combining the predicted signal power spectrum and the noise power spectrum, and are respectively:
Figure 662569DEST_PATH_IMAGE033
Figure 39192DEST_PATH_IMAGE034
Figure 63649DEST_PATH_IMAGE035
wherein
Figure 692076DEST_PATH_IMAGE036
Figure 78950DEST_PATH_IMAGE037
Figure 688791DEST_PATH_IMAGE038
Figure 262861DEST_PATH_IMAGE039
Figure 694979DEST_PATH_IMAGE040
is a difference signal between the predicted speech signal of the first channel and the predicted speech signal of the second channel,
Figure 772526DEST_PATH_IMAGE041
and
Figure 507264DEST_PATH_IMAGE042
channel parameters for the first channel and the second channel respectively,
Figure 303050DEST_PATH_IMAGE043
Figure 476542DEST_PATH_IMAGE044
is the frequency domain adaptive filter gain obtained according to the wiener filter improvement.
In order to realize the suppression of noise in a telephone set and external background noise in the VoIP call process and make the voice call as close as possible to the real person speaking. The noise reduction method based on the double microphones has a good noise reduction effect in the range of 1m from the microphone in the call, and has high speech restoration degree.
Because the technical scheme provided by the invention takes the channel signal-to-noise ratio and the correlation between the two channels as the judgment basis for predicting the signal power spectrum, better filtering can be more accurately provided for the signal section with more noise components, and the speech definition is kept as much as possible for the signal section with the dominant speech components, so that the speech in the conversation process is kept at higher restoration degree. In addition, the scheme provided by the invention uses the buffer to store the real-time data required by calculating the predicted signal power spectrum and the predicted noise power spectrum, and has low algorithm complexity, so that the voice noise reduction module has short time consumption, and the real-time performance of voice call is ensured.
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FIG. 1 is a block diagram of the process from sound acquisition to noise reduction and output of the method of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clearly and clearly understood, the technical solutions in the embodiments of the present invention are described below in conjunction with the accompanying drawings and the embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. All other embodiments that can be derived by one skilled in the art from the embodiments given herein are intended to be within the scope of the invention.
The basic principle of the invention is as follows: the noise elimination effect of the VoIP terminal is achieved by adopting a mode of combining spectral subtraction and adaptive noise elimination. According to signals collected by the two microphones, a predicted noise power spectrum and a predicted signal power spectrum are obtained, adaptive filters are designed according to the predicted noise power spectrum and the predicted signal power spectrum, the two sound channels are filtered respectively, and parameters are adjusted to enable the noise reduction effect to be optimal. The invention predicts the noise power spectrum in the conversation process based on the signal collected at the initial section of the conversation. The predicted signal power spectrum is obtained by carrying out weighted average on the current signal power spectrum and the adjacent previous frame signal power spectrum according to the self-adaptive prediction coefficient. The signal power spectrum prediction coefficient is obtained by adjusting the signal-to-noise ratio of the signal and the correlation coefficient modulus of the two channels.
The embodiment of the invention provides a method for reducing noise of a VoIP (voice over Internet protocol) calling device for collecting sound by double channels, which is characterized in that according to the principle that sound signals collected by the two channels have certain relativity and independence, the signal-to-noise ratio of the signals is used as the basis for adjusting the prediction coefficient of the power spectrum prediction of the current signals, so that the self-adaptive prediction of the power spectrums of the two channels of signals is realized, meanwhile, the tracking prediction is carried out on a noise section, and the noise reduction performance of a noise reduction filter is improved.
FIG. 1 is a block diagram of the process from sound acquisition to noise reduction and output of the method of the present invention. As shown in the figure, the main content of the present invention includes the following steps:
step 1: collecting the voice signal containing noise for the No. 1 microphone of the VoIP terminal and recording as
Figure 611858DEST_PATH_IMAGE045
And 2, the microphone device collects the voice signal containing noise and records the signal
Figure 829081DEST_PATH_IMAGE046
Step 2: to pair
Figure 862896DEST_PATH_IMAGE045
And
Figure 574500DEST_PATH_IMAGE047
and respectively carrying out frame division processing, wherein the frame length of each frame is fixed.
And step 3: calculating the module value of the coherent coefficient of the 1, 2-channel frame signal
Figure 564322DEST_PATH_IMAGE001
And 4, step 4: the 1, 2-channel frame signal is subjected to fft (discrete fourier transform) after being subjected to rectangular windowing.
And 5: and calculating a power spectrum of the signal containing the noise according to the fft coefficient of the frame signal.
Step 6: and carrying out noise power spectrum prediction on the noise section of the 1, 2-channel frame signal.
And 7: and obtaining the predicted power spectrum of the 1, 2-channel frame signal according to the prediction coefficient.
The prediction coefficient of the power spectrum is obtained according to the signal-to-noise ratio, and the power spectrum prediction method has the function of adaptively adjusting signal prediction. In order to obtain a stable noise signal more accurately, the scheme adopts a fixed prediction coefficient to track and predict a noise section signal.
And 8: and calculating the adjustment gain of each frequency line of the 1 and 2 channel frame signals according to the power spectrum and the noise power spectrum of the obtained predicted signals.
And step 9: and (4) adjusting gain according to the frame signal frequency domain obtained in the step (8), realizing self-adaptive filtering of the frame signal, and performing fft inverse transformation on the filtered signal to obtain a clear voice signal subjected to noise reduction and filtering.
The specific embodiment is as follows:
in step 1, the microphone 1 and the microphone 2 built in the VoIP terminal start to collect signals from the successful call connection, and the collected signals are voice signals containing noise. The contained noise mainly comprises two parts of built-in noise generated in the operation process of the VoIP terminal and external noise in the conversation environment. 1-channel noise-containing voice signal acquired by No. 1 microphone is converted into 1-channel discrete number through analog-to-digital conversion moduleWord-containing noisy speech signal, denoted as
Figure 827813DEST_PATH_IMAGE045
. 2-channel noise-containing signals collected by the No. 2 microphone are converted into 2-channel discrete digital noise-containing voice signals through the analog-to-digital conversion module, and the 2-channel discrete digital noise-containing voice signals are recorded as
Figure 411241DEST_PATH_IMAGE046
Wherein, No. 1 microphone and No. 2 microphone are located VoIP terminal inside left side and right side respectively to gather sound signal from different directions, avoid the conversation in-process sound signal to appear the directionality. Microphones # 1 and # 2 are placed closer together. Because the position and the direction of the two microphones for collecting the sound signals are different, the energy of the sound signals collected by the two microphones is greatly different, and because the two microphones are placed at a close distance, the noise signals collected by the two microphones have more related parts.
Step 2: for collected
Figure 660957DEST_PATH_IMAGE045
And
Figure 833181DEST_PATH_IMAGE046
the discrete digital signal is framed by using 160 discrete voice signal points as a frame so as to carry out real-time adaptive noise reduction processing on the discrete digital signal. Will be the first in the 1-channel frame signal
Figure 205257DEST_PATH_IMAGE008
A sampling point signal is recorded as
Figure 275981DEST_PATH_IMAGE007
2 th channel frame signal
Figure 952556DEST_PATH_IMAGE008
A sampling point signal is recorded as
Figure 979287DEST_PATH_IMAGE009
The beginning of the adaptive noise reduction of the discrete time domain frame signal is not marked by the formal conversation of the VoIP terminals, but is marked by the successful establishment of the conversation between the VoIP terminals. Therefore, the accuracy of noise tracking prediction can be improved, and the situation of high noise at the beginning of a call is avoided.
And step 3: the voice component irrelevancy in the 1,2 channel signal is larger, the noise component relativity is larger, the design of the scheme is to use the module value of the coherence coefficient of the 1,2 channel frame signal
Figure 397630DEST_PATH_IMAGE001
And the prediction coefficient of the power spectrum of the 1, 2-channel prediction signal is adaptively adjusted as one of the reference factors. The scheme is designed according to the classic two-path signal correlation coefficient calculation formula
Figure 814705DEST_PATH_IMAGE001
Figure 858753DEST_PATH_IMAGE002
Wherein,
Figure 553040DEST_PATH_IMAGE003
and
Figure 329235DEST_PATH_IMAGE004
the mean values of the 1 and 2-channel discrete time domain frame signals respectively are calculated according to the following formula:
Figure 374551DEST_PATH_IMAGE005
Figure 707443DEST_PATH_IMAGE006
and 4, step 4: performing fft transformation after adding a window function to the 1, 2-channel discrete time domain frame signals to obtain the frequency spectrum coefficients of the two channel frame signals, and converting the 1 st channel frame signal
Figure 66356DEST_PATH_IMAGE048
A spectral coefficient is recorded as
Figure 279032DEST_PATH_IMAGE013
2 nd channel frame signal
Figure 546065DEST_PATH_IMAGE048
A spectral coefficient is recorded as
Figure 682648DEST_PATH_IMAGE014
Figure 210581DEST_PATH_IMAGE049
The window functions are more selective, mainly comprise a rectangular window, a Hamming window, a Hanning window and the like, different windowing functions can be selected according to actual needs and effects, and in the embodiment of the invention, the rectangular window has a better effect, so that the rectangular window is designed and selected as the fft transformation windowing function.
And 5: calculating the power spectrums of the 1-channel frame signal and the 2-channel frame signal according to the 1-channel frame spectrum coefficient and the 2-channel frame spectrum coefficient obtained in the step 4, and respectively recording the power spectrums as
Figure 594158DEST_PATH_IMAGE010
Figure 348488DEST_PATH_IMAGE011
The formula is as follows:
Figure 482838DEST_PATH_IMAGE015
Figure 130857DEST_PATH_IMAGE016
wherein, the power spectrum of the frame signal is the square of the amplitude of discrete Fourier transform of the frame signal. The general spectral coefficient is composed of a real part and an imaginary part, and for any spectral coefficient
Figure 934603DEST_PATH_IMAGE050
All can be expressed as
Figure 35283DEST_PATH_IMAGE051
Figure 762937DEST_PATH_IMAGE052
To be considered as a part of it,
Figure 406408DEST_PATH_IMAGE053
for its imaginary part, its corresponding power spectrum calculation formula can be expressed as:
Figure 679257DEST_PATH_IMAGE054
the scheme of the invention respectively predicts the power spectrum of the noise-containing signal and the power spectrum of the noise signal of the channels 1 and 2, and obtains the self-adaptive frequency domain gain coefficient for filtering the current frame signal according to the prediction result. In order to update the voice component and the noise component in the call process in real time so as to enable the prediction result to be more accurate, the predicted signal power spectrum and the noise power spectrum are obtained according to the signal power spectrum and the noise power spectrum of the previous adjacent frame and the current frame. The scheme of the invention is provided with a frame signal power spectrum buffer to store the signal power spectrum of the adjacent previous frame and a noise power spectrum buffer to store the noise power spectrum of the adjacent previous frame. Recording the power spectrums of the 1 and 2 channels of the previous adjacent frame stored in the power spectrum buffer as the power spectrums of the signals
Figure 532812DEST_PATH_IMAGE028
Figure 798578DEST_PATH_IMAGE029
The noise power spectrum of the adjacent previous frame stored in the noise power spectrum buffer is recorded as
Figure 234238DEST_PATH_IMAGE055
Step 6: and (5) calculating the noise power spectrum of the current frame according to the noise power spectrum in the noise power spectrum buffer and the signal power spectrum of the current frame calculated in the step (5). 1,2 are mixedThe noise power spectrum of the current frame of the channel is respectively recorded as
Figure 864940DEST_PATH_IMAGE056
The calculation formula is as follows:
Figure 268108DEST_PATH_IMAGE057
Figure 275247DEST_PATH_IMAGE058
for the first frame signal, the noise buffer stores initialized data, which is usually all 0 data, and the data in the noise buffer used by the following frame is the noise power spectrum of the previous adjacent frame. Since there is a short time interval between successful call setup of the VoIP terminal and normal call, both channel signals collected by the microphones are basically noise signal components, and this time interval is generally about 2 s. The noise interval is assumed to be 0.5s, and since the sampling rate of the speech signal in the case of the present invention is 16khz, the interval of 0.5 is the discrete digital signal of the first 50 frames, which is basically a noise signal, and therefore the noise signal is tracked and predicted in the first 50 frames. In order to avoid erroneous judgment of the speech signal as a noise component and generation of erroneous interference on a noise prediction result, noise tracking prediction is not performed on a signal after 50 frames, and stable noise predicted by the previous 50 frames is used as a frame noise signal to calculate a predicted signal power spectrum.
And 7: according to the predicted signal-to-noise ratio, the correlation coefficient module value calculated in step 3
Figure 627731DEST_PATH_IMAGE001
And 5, calculating the power spectrum of the predicted signal according to the power spectrum of the current frame signal calculated in the step 5 and the data in the signal power spectrum buffer. The predicted signal-to-noise ratio is calculated according to the predicted signal power spectrum and the noise signal power spectrum of the adjacent previous frame signal of 1 channel, and is recorded as
Figure 632596DEST_PATH_IMAGE059
And 1 channel is selected for calculation without influence in the scheme of the invention. The predicted signal power spectrum is obtained by performing weighting operation on the signal power spectrum and data in the signal power spectrum buffer according to the self-adaptive prediction coefficient. Recording the adaptive prediction coefficient as
Figure 257481DEST_PATH_IMAGE060
Which is based on
Figure 615782DEST_PATH_IMAGE001
And performing adaptive adjustment to obtain the product. The power spectrum of the predicted signal of the 1,2 channels is recorded as
Figure 88351DEST_PATH_IMAGE061
. Because the calculation of the predicted signal-to-noise ratio needs to be carried out according to the predicted signal power spectrum and the noise power spectrum of the adjacent previous frame, the invention is provided with a predicted signal power spectrum buffer, and the predicted signal power spectrum of the adjacent previous frame of the 1,2 channels stored in the predicted signal power spectrum buffer is recorded as the predicted signal power spectrum of the adjacent previous frame of the 1,2 channels
Figure 123172DEST_PATH_IMAGE062
7-a, calculating a predicted signal-to-noise ratio according to data in the predicted signal power spectrum buffer and data in the noise power spectrum buffer:
Figure 986086DEST_PATH_IMAGE032
Figure 335028DEST_PATH_IMAGE031
calculating the value of the adaptive prediction coefficient according to the size of the predicted signal-to-noise ratio:
Figure 973688DEST_PATH_IMAGE030
Figure 195722DEST_PATH_IMAGE031
7-c, in order to avoid the influence of too large or too small self-adaptive prediction coefficient on the power spectrum of the prediction signal, adjusting the value range of the self-adaptive prediction coefficient to control the value range to be 0-0.95:
Figure 919833DEST_PATH_IMAGE063
and 7-d, calculating to obtain a predicted signal power spectrum according to the adaptive prediction coefficient:
Figure 806887DEST_PATH_IMAGE025
Figure 988470DEST_PATH_IMAGE026
Figure 381405DEST_PATH_IMAGE027
for the first frame signal, the signal power spectrum buffer and the data in the predicted signal power spectrum buffer are initialized data, which are all 0 data in general, and for other frame signals, the data stored in the buffer is the data of the corresponding adjacent previous frame. After the predicted signal power spectrum of the current frame is obtained through calculation, data in the three buffers, namely the noise power spectrum buffer, the signal power spectrum buffer and the predicted signal power spectrum buffer, in the case of the invention are updated in real time.
And 8: and calculating the frequency domain coefficient self-adaptive adjustment gain of the current frame signal according to the noise power spectrum obtained in the step 6 and the predicted signal power spectrum obtained in the step 7. Will 1 channel frame signal
Figure 468178DEST_PATH_IMAGE048
The gain corresponding to the root frequency line is recorded as
Figure 345873DEST_PATH_IMAGE043
2 nd channel frame signal
Figure 506596DEST_PATH_IMAGE048
The gain corresponding to the root frequency line is recorded as
Figure 319700DEST_PATH_IMAGE044
The calculation formula is as follows:
Figure 956087DEST_PATH_IMAGE033
Figure 997992DEST_PATH_IMAGE034
Figure 154167DEST_PATH_IMAGE027
wherein,
Figure 138173DEST_PATH_IMAGE036
Figure 684691DEST_PATH_IMAGE037
Figure 68572DEST_PATH_IMAGE038
Figure 16936DEST_PATH_IMAGE027
wherein,
Figure 109526DEST_PATH_IMAGE040
predicting a difference signal of the speech signal for two channels, and
Figure 205658DEST_PATH_IMAGE041
and
Figure 838634DEST_PATH_IMAGE042
channel parameters for the 1,2 channels respectively,
Figure 969401DEST_PATH_IMAGE043
Figure 232892DEST_PATH_IMAGE044
is the frequency domain adaptive filter gain obtained according to the wiener filter improvement.
And step 9: filtering the frame signals of the 1,2 channels according to the signal frequency domain adjusting gain obtained in the step 8, then inversely transforming the filtered frequency domain coefficient into a time domain signal to obtain the 1,2 channel voice signal subjected to noise reduction processing by a noise reduction method based on the binaural power spectrum adaptive prediction, and recording the frame signal subjected to the noise reduction of the 1 channel as the frame signal subjected to the noise reduction of the 1 channel
Figure DEST_PATH_IMAGE064
And the 2-channel noise-reduced frame signal is recorded as
Figure DEST_PATH_IMAGE065
Wherein
Figure 65588DEST_PATH_IMAGE027
Figure DEST_PATH_IMAGE066
For inverse fourier transform:
Figure DEST_PATH_IMAGE067
the above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (9)

1. A noise reduction method based on double microphones is characterized by mainly comprising the following steps:
step a: the method comprises the steps that a first channel collects a first voice signal containing noise from a first microphone, a second channel collects a second voice signal containing noise from a second microphone, and the first voice signal and the second voice signal are sampled and then are subjected to framing processing respectively to obtain a first channel frame signal and a second channel frame signal;
step b: calculating a coherence coefficient modulus r of the first channel frame signal and the second channel frame signal;
step c: respectively calculating the power spectrum of the frame signal according to the first channel frame signal and the second channel frame signal, and respectively predicting the noise power spectrum;
step d: calculating a predicted signal power spectrum according to a predicted signal-to-noise ratio, the coherence coefficient module value r, a current frame signal power spectrum, a previous frame noise power spectrum and a previous frame signal power spectrum, and calculating each frequency line adjustment gain of the first channel frame signal and the second channel frame signal by combining the predicted signal power spectrum and the noise power spectrum, so as to finally realize the self-adaptive filtering of the first channel frame signal and the second channel frame signal, wherein the coherence coefficient module value r is as follows:
Figure FDA0002770322570000011
wherein the ave1 and the ave2 are mean values of the discrete time domain frame signals of the first channel and the second channel, respectively, and the calculation formula is as follows:
Figure FDA0002770322570000012
the ith sampling point signal in the first channel frame signal is marked as f1(i) 1, 2., 160, where the ith sampling point signal in the second channel frame signal is denoted as f2(i),i=1,2,...,160。
2. The noise reduction method according to claim 1, wherein the power spectrums of the frame signals of the first channel and the second channel are respectively expressed as: p1(k),P2(k) The k-th spectral coefficient of the first channel frame signal is denoted as F1(k) The k-th spectral coefficient of the second channel frame signal is marked as F2(k) The formula of the frame signal power spectrum is as follows:
P1(k)=|F1(k)|2
P2(k)=|F2(k)|2and k is 1,2, …,160, where f (k) is a + bj, a is its real part and b is its imaginary part.
3. The noise reduction method according to claim 2, wherein the current frame noise power spectrums of the first channel frame signal and the second channel frame signal are respectively denoted as n1(k),n2(k) K is 1,2, …,160, and the noise power spectrum of the previous frame of the first channel frame signal and the second channel frame signal is recorded as n1 -1(k),n2 -1(k) K is 1,2, …,160, and the calculation formula is as follows:
n1(k)=0.95*n1 -1(k)+0.05*P1(k)
n2(k)=0.95*n2 -1(k)+0.05*P2(k),k=1,2,…,160。
4. the noise reduction method according to claim 3, wherein the predicted signal power spectrum is calculated by the following formula:
Figure FDA0002770322570000021
wherein, the P-1 1(k) And said P-1 2(k) The power spectrum of the signal of the previous frame of the first channel and the second channel respectively, the
Figure FDA0002770322570000022
And said
Figure FDA0002770322570000023
Predicting signal power spectra for previous frames of said first channel and said second channel, respectively, with adaptive prediction coefficients of
Figure FDA0002770322570000024
The predictionThe signal-to-noise ratio is:
Figure FDA0002770322570000025
5. the noise reduction method according to claim 4, wherein the frequency-domain adjustment gains of the first channel frame signal and the second channel frame signal are calculated by combining the predicted signal power spectrum and the noise power spectrum, and are respectively:
Figure FDA0002770322570000026
wherein,
Figure FDA0002770322570000027
Figure FDA0002770322570000028
the SS (k) is a difference signal between the predicted speech signal of the first channel and the predicted speech signal of the second channel, and the H1(k) and the H2(k) are channel parameters, G, of the first channel and the second channel, respectively1(k),G2(k) Is the frequency domain adaptive filter gain obtained according to the wiener filter improvement.
6. The noise reduction method according to claim 5, wherein the first speech signal and the second speech signal are sampled at a sampling rate of 16khz, and the noise signal is subjected to tracking prediction in the first 50 frames.
7. The noise reduction method according to claim 6, wherein the previous frame noise power spectrum is stored in a noise power spectrum buffer; the signal power spectrum of the previous frame is stored in a signal power spectrum buffer; the predicted signal power spectrum of the previous frame is stored in a predicted signal power spectrum buffer.
8. The method of claim 7, wherein the first channel frame signal and the second channel frame signal are filtered according to the frequency domain adjustment gain, and then the filtered frequency domain coefficients are inversely transformed into time domain signals, so as to obtain the first channel speech signal and the second channel speech signal after the noise reduction.
9. The method of reducing noise according to claim 8, wherein data in the noise power spectrum buffer, the signal power spectrum buffer and the predicted signal power spectrum buffer is updated in real time.
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