US9271075B2 - Signal processing apparatus and signal processing method - Google Patents
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- H04R3/00—Circuits for transducers, loudspeakers or microphones
- H04R3/005—Circuits for transducers, loudspeakers or microphones for combining the signals of two or more microphones
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
- G10L25/00—Speech or voice analysis techniques not restricted to a single one of groups G10L15/00 - G10L21/00
- G10L25/78—Detection of presence or absence of voice signals
- G10L25/84—Detection of presence or absence of voice signals for discriminating voice from noise
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- H04R1/00—Details of transducers, loudspeakers or microphones
- H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
- H04R1/32—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only
- H04R1/40—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only by combining a number of identical transducers
- H04R1/406—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only by combining a number of identical transducers microphones
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- G10L21/00—Speech or voice signal processing techniques to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility
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- H04R2201/00—Details of transducers, loudspeakers or microphones covered by H04R1/00 but not provided for in any of its subgroups
- H04R2201/40—Details of arrangements for obtaining desired directional characteristic by combining a number of identical transducers covered by H04R1/40 but not provided for in any of its subgroups
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- H04R2410/07—Mechanical or electrical reduction of wind noise generated by wind passing a microphone
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- H04R2499/10—General applications
- H04R2499/11—Transducers incorporated or for use in hand-held devices, e.g. mobile phones, PDA's, camera's
Definitions
- FIG. 10 is a diagram illustrating an example of the conventional apparatus. As illustrated in FIG. 10 , a conventional apparatus 10 is connected to microphones 10 a and 10 b . The microphones 10 a and 10 b are spaced apart from each other by a predetermined distance.
- the conventional apparatus 10 includes a correlation analyzer 11 , a noise analyzer 12 , and a noise reduction unit 13 .
- the microphone 10 a is a microphone which converts collected sound into an input signal Lin(t) and outputs the input signal Lin(t) to the conventional apparatus 10 .
- the microphone 10 b is a microphone which converts collected sound into an input signal Rin(t) and outputs the input signal Rin(t) to the conventional apparatus 10 .
- t corresponds to a sampling number of the input signal.
- the correlation analyzer 11 calculates a correlation value r(t) between the input signal Lin(t) and the input signal Rin(t) by using the formula (1).
- the correlation analyzer 11 sequentially changes the value of i from 1 to n and calculates a correlation value r(t). For example, the value of n is 128.
- the correlation analyzer 11 outputs the correlation value r(t) to the noise analyzer 12 .
- r ( t ) ⁇ L in( t ⁇ i ) R in( t ⁇ i )/(( ⁇ L in( t ⁇ i ) 2 ) 1/2 ( ⁇ R in( t ⁇ i ) 2 ) 1/2 ) (1)
- the noise analyzer 12 determines that there is noise of wind and outputs control information to turn down volume to the noise reduction unit 13 .
- the noise reduction unit 13 adjusts the volumes of the input signals Lin(t) and Rin(t) and outputs the input signals Lin(t) and Rin(t) to an external apparatus. For example, when the noise reduction unit 13 receives the control information to turn down volume, the noise reduction unit 13 turns down the volumes of the input signals Lin(t) and Rin(t) and outputs the input signals Lin(t) and Rin(t) to the external apparatus.
- Patent Document 1 Japanese Laid-open Patent Publication No. 2004-289762
- Patent Document 2 Japanese Laid-open Patent Publication No. 2009-005133
- a signal processing apparatus includes: an adder that acquires a plurality of input signals from a plurality of microphones and calculates an added value obtained by adding the input signals together; a subtracter that acquires a plurality of input signals from the plurality of microphones and calculates a subtracted value obtained by subtracting one input signal from the other input signal; and a determination unit that determines whether noise is included in the input signals based on the added value and the subtracted value.
- FIG. 1 is a diagram illustrating a configuration of a signal processing apparatus according to a first embodiment
- FIG. 2 is a flowchart illustrating a processing procedure of the signal processing apparatus according to the first embodiment
- FIG. 3 is a diagram for explaining an effect of the present invention compared with a conventional apparatus
- FIG. 4 is a diagram illustrating a configuration of a signal processing apparatus according to a second embodiment
- FIG. 5 is a flowchart illustrating a processing procedure of the signal processing apparatus according to the second embodiment
- FIG. 6 is a diagram illustrating a configuration of a signal processing apparatus according to a third embodiment
- FIG. 7 is a flowchart illustrating a processing procedure of the signal processing apparatus according to the third embodiment.
- FIG. 8 is a diagram for explaining another process of a gain calculator
- FIG. 9 is a diagram illustrating an example of a computer that executes a signal processing program.
- FIG. 10 is a diagram illustrating an example of a conventional apparatus.
- FIG. 1 is a diagram illustrating a configuration of a signal processing apparatus according to a first embodiment. As illustrated in FIG. 1 , a signal processing apparatus 100 is connected to microphones 10 a and 10 b . The microphones 10 a and 10 b are spaced apart from each other by a predetermined distance.
- the signal processing apparatus 100 includes an adder 110 , a subtracter 120 , and power calculators 130 a and 130 b .
- the signal processing apparatus 100 also includes a ratio calculator 140 , a determination unit 150 , a gain calculator 160 , and a noise suppression unit 170 .
- the microphone 10 a is a microphone which converts collected sound into an input signal Lin(t) and outputs the input signal Lin(t) to the signal processing apparatus 100 .
- the microphone 10 b is a microphone which converts collected sound into an input signal Rin(t) and outputs the input signal Rin(t) to the signal processing apparatus 100 .
- t corresponds to a sampling number of the input signal.
- the adder 110 calculates an added value p(t) by adding the input signal Lin(t) and the input signal Rin(t) together.
- the added value p(t) is represented by the formula (2).
- the adder 110 outputs the added value p(t) to the power calculator 130 a.
- p ( t ) L in( t )+ R in( t ) (2)
- the subtracter 120 calculates an subtracted value m(t) by subtracting the input signal Rin(t) from the input signal Lin(t).
- the subtracted value m(t) is represented by the formula (3).
- the subtracter 120 outputs the subtracted value m(t) to the power calculator 130 b.
- m ( t ) L in( t ) ⁇ R in( t ) (3)
- the power calculator 130 a calculates a power Ppow(t) by summing up squared values of the added value p(t) of different sampling numbers.
- the power Ppow(t) is represented by the formula (4).
- the power calculator 130 a sequentially changes the value of j from 1 to n and calculates the power Ppow(t).
- the value of n is a natural number. For example, the value of n is 128.
- the power calculator 130 a outputs the power Ppow(t) to the ratio calculator 140 .
- P pow( t ) ⁇ p ( t ⁇ j ) 2 (4)
- the power calculator 130 b calculates a power Mpow(t) by summing up squared values of the subtracted value m(t) of different sampling numbers.
- the power Mpow(t) is represented by the formula (5).
- the power calculator 130 b sequentially changes the value of j from 1 to n and calculates the power Mpow(t).
- the value of n is a natural number. For example, the value of n is 128.
- the power calculator 130 b outputs the power Mpow(t) to the ratio calculator 140 .
- M pow( t ) ⁇ m ( t ⁇ j ) 2 (5)
- the ratio calculator 140 calculates a ratio v(t) of the power Ppow(t) and the power Mpow(t). For example, the ratio calculator 140 calculates the ratio v(t) by the formula (6). The ratio calculator 140 outputs the ratio v(t) to the determination unit 150 and the gain calculator 160 .
- v(t) may be a square root of the ratio of the power Ppow(t) and the power Mpow(t).
- v ( t ) M pow( t )/ P pow( t ) (6)
- the determination unit 150 determines whether noise is included in the input signals Lin(t) and Rin(t) based on the ratio v(t). When the value of the ratio v(t) is greater than or equal to a predetermined threshold value, the determination unit 150 determines that noise is included in the input signals Lin(t) and Rin(t). The determination unit 150 outputs a determination result to the gain calculator 160 .
- the gain calculator 160 calculates a gain based on the ratio v(t).
- the gain calculator 160 first calculates g′(t) by the formula (7) and thereafter calculates a gain g(t) by the formula (8).
- g ′( t ) 1 ⁇ v ( t ) (7)
- g ( t ) max( g ′( t ), ⁇ ) (8)
- ⁇ is a lower limit value greater than or equal to 0 and smaller than or equal to 1.
- the gain calculator 160 calculates g′(t) and thereafter calculates the larger value of g′(t) and ⁇ as the gain g(t).
- the gain calculator 160 outputs the gain g(t) to the noise suppression unit 170 .
- the gain calculator 160 may calculate the gain g(t) when noise is included in the input signals Lin(t) and Rin(t) based on the determination result of the determination unit 150 . On the other hand, when noise is not included in the input signals Lin(t) and Rin(t), the gain calculator 160 may set 1 to the gain g(t) and output the gain g(t) to the noise suppression unit 170 .
- the noise suppression unit 170 suppresses noise by multiplying the input signals Lin(t) and Rin(t) by the gain g(t). For example, the noise suppression unit 170 generates output signals Lout(t) and Rout(t) from the input signals Lin(t) and Rin(t) and outputs the generated signals to an external apparatus.
- FIG. 2 is a flowchart illustrating a processing procedure of the signal processing apparatus according to the first embodiment.
- the process illustrated in FIG. 2 is performed when input signals are received from the microphones 10 a and 10 b.
- the signal processing apparatus 100 calculates the added value p(t) obtained by adding together the input signals Lin(t) and Rin(t) of the microphones 10 a and 10 b (step S 101 ).
- the signal processing apparatus 100 calculates the subtracted value m(t) obtained by subtracting the input signal Rin(t) of one microphone 10 b from the input signal Lin(t) of the other microphone 10 a (step S 102 ).
- the signal processing apparatus 100 calculates the power Ppow(t) based on the added value p(t) (step S 103 ).
- the signal processing apparatus 100 calculates the power Mpow(t) based on the subtracted value m(t) (step S 104 ).
- the signal processing apparatus 100 calculates the ratio v(t) (step S 105 ) and determines whether noise is included (step S 106 ).
- the signal processing apparatus 100 calculates the gain g(t) based on the ratio v(t) (step S 107 ).
- the signal processing apparatus 100 outputs the output signals Lout(t) and Rout(t) whose noise is suppressed based on the gain g(t) (step S 108 ).
- the determination unit 150 determines whether noise is included in the input signals Lin(t) and Rin(t) based on the added value p(t) calculated by the adder 110 and the subtracted value m(t) calculated by the subtracter 120 . Therefore, it is possible to accurately determine whether noise is included, so that noise included in the input signals can be sufficiently suppressed by using the determination result.
- the lower the frequency the stronger the correlation between the input signals. This is because the lower the frequency, the smaller the variation of waveforms in the time axis direction, so that the waveforms have similar shapes.
- An extreme example is a direct current. Therefore, in order to strengthen the correlation, the adder 110 sums up the input signals. On the other hand, in order to suppress the correlation, the subtracter 120 subtracts one input signal from the other input signal.
- noise can be accurately detected by using the ratio of the “power of (Lin(t) ⁇ Rin(t))” based on the “power of (Lin(t)+Rin(t))”. Also, an appropriate gain can be calculated by using the ratio of the “power of (Lin(t)-Rin(t))” based on the “power of (Lin(t)+Rin(t))”, and a noise component included in the input signals can be suppressed by using the gain.
- FIG. 3 is a diagram for explaining an effect of the present invention compared with a conventional apparatus.
- Signals 20 A in FIG. 3 indicates a relationship between the sampling number and the gain g(t) of the conventional apparatus.
- Signals 20 B in FIG. 3 indicates a relationship between the sampling number and the gain g(t) of the signal processing apparatus 100 .
- Sections 21 in the signals 20 A and 20 B are sections including voice.
- the gain g(t) in sections including only wind hitting noise is reduced while the gain g(t) in the sections 21 is substantially maintained at 1. Therefore, in the present invention, it is possible to turn down volume of a part of input signals including noise without turning down volume of whole input signals in voice sections.
- the determination unit 150 determines whether noise is included based on the value of the ratio v(t). However, it is not limited to this.
- the determination unit 150 may obtain a difference between the Ppow(t) and the Mpow(t), and when the difference value is smaller than a predetermined threshold value, the determination unit 150 may determine that noise is included in the input signals.
- the signal processing apparatus 100 may be configured by integrating the determination unit 150 and the gain calculator 160 together.
- FIG. 4 is a diagram illustrating a configuration of the signal processing apparatus according to the second embodiment.
- a signal processing apparatus 200 is connected to the microphones 10 a and 10 b .
- the microphones 10 a and 10 b are spaced apart from each other by a predetermined distance.
- the description about the microphones 10 a and 10 b is the same as that in the first embodiment.
- the signal processing apparatus 200 includes a delay detector 201 and delay devices 202 a and 202 b .
- the signal processing apparatus 200 also includes an adder 210 , a subtracter 220 , and power calculators 230 a and 230 b .
- the signal processing apparatus 200 also includes a ratio calculator 240 , a determination unit 250 , a gain calculator 260 , and a noise suppression unit 270 .
- the delay detector 201 calculates a correlation coefficient c(d) between the input signal Lin(t) and the input signal Rin(t) by the formula (13).
- the delay detector 201 changes a delay amount d and detects a delay amount dmax by which the value of correlation coefficient c(d) is the maximum.
- c ( d ) ⁇ L in( t ) R in( t ⁇ d )/(( ⁇ L in( t ) 2 ) 1/2 ( ⁇ R in( t ⁇ d ) 2 ) 1/2 ) (13)
- the delay detector 201 calculates a delay amount dL applied to the input signal from the microphone 10 a and a delay amount dR applied to the input signal from the microphone 10 b in order to synchronize the input signals inputted from the microphones 10 a and 10 b .
- a calculation example of the delay amounts dL and dR will be described below.
- the delay detector 201 sets the value of dL to 0 and sets the value of dR to the value of the dmax. Then, the delay detector 201 outputs the dL to the delay device 202 a and outputs the dR to the delay device 202 b.
- the delay detector 201 sets the value of dL to the absolute value of the dmax and sets the value of dR to 0. Then, the delay detector 201 outputs the dL to the delay device 202 a and outputs the dR to the delay device 202 b.
- the delay device 202 a performs a delay process of the input signal Lin(t) from the microphone 10 a .
- the delay device 202 a outputs an input signal Lin(t ⁇ dL) obtained by performing a delay process on the input signal Lin(t) to the adder 210 and the subtracter 220 .
- the adder 210 calculates an added value p(t) by adding together the input signals Lin(t ⁇ dL) and Rin(t ⁇ dR) whose delay amounts are adjusted.
- the adder 210 outputs the added value p(t) to the power calculator 230 a.
- the descriptions about the power calculators 230 a and 230 b , the ratio calculator 240 , the determination unit 250 , the gain calculator 260 , and the noise suppression unit 270 are the same as those of the power calculators 130 a and 130 b , the ratio calculator 140 , the determination unit 150 , the gain calculator 160 , and the noise suppression unit 170 illustrated in FIG. 1 .
- the signal processing apparatus 200 detects the maximum value of the correlation coefficient c(d) between the input signal Lin(t) and the input signal Rin(t) and calculates the delay amounts dL and dR for synchronization (step S 201 ).
- the signal processing apparatus 200 calculates the p(t) by performing synchronous addition (step S 202 ) and calculates the m(t) by performing synchronous subtraction (step S 203 ).
- the signal processing apparatus 200 calculates the power Ppow(t) based on the added value p(t) (step S 204 ).
- the signal processing apparatus 200 calculates the power Mpow(t) based on the subtracted value m(t) (step S 205 ).
- the signal processing apparatus 200 calculates the ratio v(t) (step S 206 ) and determines whether noise is included (step S 207 ).
- the signal processing apparatus 200 calculates the gain g(t) based on the ratio v(t) (step S 208 ).
- the signal processing apparatus 200 outputs the output signals Lout(t) and Rout(t) whose noise is suppressed based on the gain g(t) (step S 209 ).
- the delay detector 201 calculates the delay amounts dL and dR and the delay devices 202 a and 202 b synchronize the input signals.
- the determination unit 250 determines whether noise is included in the input signals Lin(t) and Rin(t) based on the added value p(t) calculated by the adder 210 and the subtracted value m(t) calculated by the subtracter 220 . Therefore, even if the timings when voice of a user is collected by the microphones 10 a and 10 b are different from each other, the input signals can be synchronized by adjusting the delay amounts. Thus, it is possible to accurately determine whether noise is included in a direction of a user whose voice is desired to be recorded, so that noise included in the input signals can be suppressed by using the determination result.
- FIG. 6 is a diagram illustrating a configuration of the signal processing apparatus according to the third embodiment.
- a signal processing apparatus 300 is connected to the microphones 10 a and 10 b .
- the microphones 10 a and 10 b are spaced apart from each other by a predetermined distance.
- the description about the microphones 10 a and 10 b is the same as that in the first embodiment.
- the FFT 301 a positions a Hanning window with 50% overlap on the input signal Lin(t) acquired from the microphone 10 a and converts the input signal Lin(t) into a signal on the frequency axis by fast Fourier transform.
- the input signal Lin(t) converted into a signal on the frequency axis is represented as LIN(i, f).
- i is a number of an analysis frame on which FFT is performed and f indicates the frequency.
- the FFT 301 a outputs the LIN(i, f) to the adder 310 , the subtracter 320 , and the noise suppression unit 370 .
- the FFT 301 b positions a Hanning window with 50% overlap on the input signal Rin(t) acquired from the microphone 10 b and converts the input signal Rin(t) into a signal on the frequency axis by fast Fourier transform.
- the input signal Rin(t) converted into a signal on the frequency axis is represented as RIN(i, f).
- the FFT 301 b outputs the RIN(i, f) to the adder 310 , the subtracter 320 , and the noise suppression unit 370 .
- the FFTs 301 a and 301 b are an example of a frequency converter.
- the adder 310 is a processing unit which calculates an added value p(i, f) by adding the input signal LIN(i, f) and the input signal RIN(i, f) together.
- the added value p(i, f) is represented by the formula (14).
- the adder 310 outputs the added value p(i, f) to the power calculator 330 a.
- p ( i, f ) L IN( i, f )+ R IN( i, f ) (14)
- the subtracter 320 calculates a subtracted value m(i, f) by subtracting the input signal RIN(i, f) from the input signal LIN(i, f).
- the subtracted value m(i, f) is represented by the formula (15).
- the subtracter 320 outputs the subtracted value m(i, f) to the power calculator 330 b.
- m ( i, f ) L IN( i, f ) ⁇ R IN( i, f ) (15)
- the power calculator 330 a calculates a power Ppow(i, f) by summing up squared values of the added value p(i, f) of different frame numbers.
- the power Ppow(i, f) is represented by the formula (16).
- the power calculator 330 a sequentially changes the value of j from 1 to n and calculates the power Ppow(i, f).
- the value of n is a natural number. For example, the value of n is 128.
- the power calculator 330 a outputs the power Ppow(i, f) to the ratio calculator 340 .
- P pow( i, f ) ⁇ p ( i ⁇ j, f ) (16)
- the power calculator 330 b calculates a power Mpow(i, f) by summing up squared values of the subtracted value m(i, f) of different frame numbers.
- the power Mpow(i, f) is represented by the formula (17).
- the power calculator 330 b sequentially changes the value of j from 1 to n and calculates the power Mpow(i, f).
- the value of n is a natural number. For example, the value of n is 128.
- the power calculator 330 b outputs the power Mpow(i, f) to the ratio calculator 340 .
- M pow( i, f ) ⁇ m ( i ⁇ j, f ) (17)
- the ratio calculator 340 calculates a ratio v(i, f) of the power Ppow(i, f) and the power Mpow(i, f). For example, the ratio calculator 340 calculates the ratio v(i, f) by the formula (18). The ratio calculator 340 outputs the ratio v(i, f) to the determination unit 350 and the gain calculator 360 .
- v ( i, f ) M pow( i, f )/ P pow( i, f ) (18)
- the determination unit 350 determines whether noise is included in the input signals LIN(i, f) and RIN(i, f) based on the ratio v(i, f). When the value of the ratio v(i, f) is greater than or equal to a predetermined threshold value, the determination unit 350 determines that noise is included in the input signals LIN(i, f) and RIN(i, f). The determination unit 350 outputs a determination result to the gain calculator 360 .
- the gain calculator 360 calculates a gain based on the ratio v(i, f).
- the gain calculator 360 first calculates g′(i, f) by the formula (19) and thereafter calculates a gain g(i, f) by the formula (20).
- g ′( i, f ) 1 ⁇ v ( i, f ) (19)
- g ( i, f ) max( g ′( i, f ), ⁇ ) (20)
- ⁇ is a lower limit value greater than or equal to 0 and smaller than or equal to 1.
- the gain calculator 360 calculates g′(i, f) and thereafter calculates the larger value of g′(i, f) and ⁇ as the gain g(i, f).
- the gain calculator 360 outputs the gain g(i, f) to the noise suppression unit 370 .
- the gain calculator 360 may calculate the gain g(i, f) when noise is included in the input signals LIN(i, f) and RIN(i, f) based on the determination result of the determination unit 350 . On the other hand, when noise is not included in the input signals LIN(i, f) and RIN(i, f), the gain calculator 360 may set 1 to the gain g(i, f) and output the gain g(i, f) to the noise suppression unit 370 .
- the noise suppression unit 370 suppresses noise by multiplying the input signals LIN(i, f) and RIN(i, f) by the gain g(i, f). For example, the noise suppression unit 370 generates output signals LOUT(i, f) and ROUT (i, f) from the input signals LIN(i, f) and RIN(i, f) and outputs the generated signals to the IFFTs 371 a and 371 b .
- the output signals LOUT(i, f) and ROUT (i, f) are represented by the formulas (21) and (22).
- the IFFT 371 a is a processing unit which generates a signal Lin(t) on the time axis by performing an inverse Fourier transform and 50% overlap addition on the LOUT(i, f).
- the IFFT 371 a outputs the output signal Lin(t) to an external apparatus.
- the IFFT 371 b is a processing unit which generates a signal Rin(t) on the time axis by performing an inverse Fourier transform and 50% overlap addition on the ROUT(i, f).
- the IFFT 371 b outputs the output signal Rin(t) to an external apparatus.
- FIG. 7 is a flowchart illustrating the processing procedure of the signal processing apparatus according to the third embodiment. For example, the process illustrated in FIG. 7 is performed when input signals are received from the microphones 10 a and 10 b.
- the signal processing apparatus 300 calculates the LIN(i, f) and the RIN(i, f) by performing a Fourier transform on the input signals Lin(t) and Rin(t) of the microphones (step S 301 ).
- the signal processing apparatus 300 calculates the added value p(i, f) obtained by adding together the input signals LIN(i, f) and RIN(i, f) of the microphones (step S 302 ).
- the signal processing apparatus 300 calculates the subtracted value m(i, f) obtained by subtracting the input signal RIN(i, f) of one microphone from the input signal LIN(i, f) of the other microphone (step S 303 ).
- the signal processing apparatus 300 calculates the power Ppow(i, f) based on the added value p(i, f) (step S 304 ).
- the signal processing apparatus 300 calculates the power Mpow(i, f) based on the subtracted value m(i, f) (step S 305 ).
- the signal processing apparatus 300 calculates the ratio v(i, f) (step S 306 ) and determines whether noise is included (step S 307 ).
- the signal processing apparatus 300 calculates the gain g(i, f) based on the ratio v(i, f) (step S 308 ).
- the signal processing apparatus 300 outputs the output signals LOUT(i, f) and ROUT(i, f) whose noise is suppressed based on the gain g(i, f) (step S 309 ).
- the signal processing apparatus 300 performs an inverse Fourier transform on the output signals LOUT(i, f) and ROUT(i, f) and outputs Lout(t) and Rout(t) (step S 310 ).
- the signal processing apparatus 300 performs a Fourier transform on the input signals Lin(t) and Rin(t) and determines whether there is noise at each frequency. Then, the signal processing apparatus 300 calculates the gain g(i, f) at each frequency and multiplies the input signals LIN(i, f) and RIN(i, f) at each frequency by the gain g(i, f). Therefore, noise at each frequency can be suppressed.
- the processes of the aforementioned signal processing apparatuses 100 to 300 are an example.
- another process of the signal processing apparatuses of the present invention will be described as a fourth embodiment.
- the process according to the fourth embodiment will be described with reference to the configuration diagram in FIG. 1 .
- the gain calculator 160 calculates the gain g(t) by using the formula (7) and the formula (8), it is not limited to this.
- the gain calculator 160 may calculate the gain g(t) by using a decision table indicating a relationship between the gain g(t) and the ratio v(t) for each distance between the microphones 10 a and 10 b.
- FIG. 8 is a diagram for explaining the other process of the gain calculator.
- the gain calculator 160 defines that when the distance between the microphones 10 a and 10 b is 4.2 cm, the relationship between the gain g(t) and the ratio v(t) is a relationship changing as illustrated by a straight line 30 A in FIG. 8 .
- the relationship illustrated by the straight line 30 A corresponds to the relationship of the formula (7).
- the gain calculator 160 defines that when the distance between the microphones 10 a and 10 b is smaller than 4.2 cm, the relationship changes as illustrated by a curved line 30 B in FIG. 8 .
- the gain calculator 160 sets the change rate of the gain g(t) larger than that indicated by the straight line 30 A when the value of the ratio v(t) is about 1 to 0.8.
- the gain calculator 160 performs the process as described above, so that it is possible to accurately suppress noise corresponding to the change of characteristics of the input signals caused by the difference of the distance between the microphones.
- the gain calculator 160 may acquire information of the distance between the microphones 10 a and 10 b in any manner. A user may input the distance into the signal processing apparatus 100 by using an input device.
- the signal processing apparatus 100 may suppress noise by using microphones 10 c and 10 d not illustrated in the drawings in addition to the pair of microphones 10 a and 10 b .
- the signal processing apparatus 100 calculates the ratio v(t) from the microphones 10 a and 10 b by the same process as that in the first embodiment.
- the v(t) calculated from the microphones 10 a and 10 b is defined as v 1 ( t ).
- the ratio v(t) is calculated from the microphones 10 c and 10 d by the same process as that in the first embodiment.
- the v(t) calculated from the microphones 10 c and 10 d is defined as v 2 ( t ).
- the signal processing apparatus 100 may adjust the input signals Lin(t) and Rin(t) by the gain g(t).
- the signal processing apparatus 100 may obtain g′(t) by the formula (25) or the formula (26).
- the processes after calculating the g′(t) is the same as that in the first embodiment.
- the g′(t) may be obtained by subtracting the average value of the v 1 ( 1 ) and v 2 ( 2 ) from 1.
- g ′( t ) 1 ⁇ v 1( t ) (25)
- g ′( t ) 1 ⁇ v 2( t ) (26)
- the gain g(t) is calculated by using the microphones 10 a to 10 d , so that it is possible to accurately suppress noise of the input signals even when there are a plurality of users.
- the processing units included in the signal processing apparatuses 100 to 300 described in the first to the fourth embodiments correspond to integrated devices such as, for example, ASIC (Application Specific Integrated Circuit) and FPGA (Field Programmable Gate Array). Also, the processing units correspond to electronic circuits such as CPU and MPU (Micro Processing Unit).
- FIG. 9 is a diagram illustrating an example of the computer that executes the signal processing program.
- a computer 400 includes a CPU 401 that performs various calculation processes, an input device 402 that receives input of data from a user, and a display 403 .
- the computer 400 also includes a reading device 404 that reads a program and the like from a storage medium and an interface device 405 that transmits and receives data to and from another computer through a network.
- the computer 400 also includes microphones 406 a and 406 b .
- the computer 400 also includes a RAM 407 that temporarily stores various information and a hard disk device 408 .
- the devices 401 to 408 are connected to a bus 409 .
- the hard disk device 408 includes, for example, an addition program 408 a , a subtraction program 408 b , a power calculation program 408 c , a ratio calculation program 408 d , a determination program 408 e , a gain calculation program 408 f , and a noise suppression program 408 g .
- the CPU 401 reads the programs 408 a to 408 g and develops the programs in the RAM 407 .
- the addition program 408 a functions as an addition process 407 a .
- the subtraction program 408 b functions as a subtraction process 407 b .
- the power calculation program 408 c functions as a power calculation process 407 c .
- the ratio calculation program 408 d functions as a ratio calculation process 407 d .
- the determination program 408 e functions as a determination process 407 e .
- the gain calculation program 408 f functions as a gain calculation process 407 f .
- the noise suppression program 408 g functions as a noise suppression process 407 g.
- the addition process 407 a corresponds to the adder 110 .
- the subtraction process 407 b corresponds to the subtracter 120 .
- the power calculation process 407 c corresponds to the power calculators 130 a and 130 b .
- the ratio calculation process 407 d corresponds to the ratio calculator 140 .
- the determination process 407 e corresponds to the determination unit 150 .
- the gain calculation process 407 f corresponds to the gain calculator 160 .
- the noise suppression process 407 g corresponds to the noise suppression unit 170 .
- the programs 408 a to 408 g need not necessarily be stored in the hard disk device 408 from the beginning.
- the programs are stored in a “portable physical medium” such as a flexible disk (FD), a CD-ROM, a DVD disk, a magneto-optical disk, and an IC card which are inserted in the computer 400 .
- the computer 400 may read the programs 408 a to 408 g from these media and execute the programs.
- the programs of the signal processing apparatuses 200 and 300 described in the second to the fourth embodiments are executed by the computer 400 in the same manner as the programs of the signal processing apparatus 100 .
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Abstract
Description
r(t)=ΣLin(t−i)Rin(t−i)/((ΣLin(t−i)2)1/2(ΣRin(t−i)2)1/2) (1)
p(t)=Lin(t)+Rin(t) (2)
m(t)=Lin(t)−Rin(t) (3)
Ppow(t)=Σp(t−j)2 (4)
Mpow(t)=Σm(t−j)2 (5)
v(t)=Mpow(t)/Ppow(t) (6)
g′(t)=1−v(t) (7)
g(t)=max(g′(t),α) (8)
Lout(t)=g(t)Lin(t) (9)
Rout(t)=g(t)Rin(t) (10)
“power of(Lin(t)+Rin(t))”>>“power of(Lin(t)−Rin(t))” (11)
“power of(Lin(t)+Rin(t))”≈“power of(Lin(t)−Rin(t))” (12)
c(d)=ΣLin(t)Rin(t−d)/((ΣLin(t)2)1/2(ΣRin(t−d)2)1/2) (13)
p(i, f)=LIN(i, f)+RIN(i, f) (14)
m(i, f)=LIN(i, f)−RIN(i, f) (15)
Ppow(i, f)=Σp(i−j, f) (16)
Mpow(i, f)=Σm(i−j, f) (17)
v(i, f)=Mpow(i, f)/Ppow(i, f) (18)
g′(i, f)=1−v(i, f) (19)
g(i, f)=max(g′(i, f),α) (20)
LOUT(i, f)=g(i, f)LIN(i, f) (21)
ROUT(i, f)=g(i, f)RIN(i, f) (22)
Pamp(t)=Σ|p(t−j)| (23)
Mamp(t)=Σ|m(t−j)| (24)
g′(t)=1−v1(t) (25)
g′(t)=1−v2(t) (26)
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US9271100B2 (en) | 2013-06-20 | 2016-02-23 | 2236008 Ontario Inc. | Sound field spatial stabilizer with spectral coherence compensation |
CN104282303B (en) | 2013-07-09 | 2019-03-29 | 威盛电子股份有限公司 | The method and its electronic device of speech recognition are carried out using Application on Voiceprint Recognition |
EP3163903B1 (en) * | 2015-10-26 | 2019-06-19 | Nxp B.V. | Accoustic processor for a mobile device |
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US20130156221A1 (en) | 2013-06-20 |
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