JP5641187B2 - Sound processor - Google Patents

Description

  The present invention is a component in which a sound image is localized at a target position (direction) in a stereo format acoustic signal (for example, a component included in each signal of a right channel and a left channel. Hereinafter, referred to as a “localization component”). It is related with the technology which emphasizes or suppresses.

  Conventionally, a technique for suppressing a predetermined localization component from an acoustic signal recorded on a recording medium such as a CD has been proposed. For example, Patent Document 1 discloses a technique for suppressing a component (typically a singing sound) in which a sound image is localized in the center direction by subtracting one of stereo audio signals from the other (reverse phase addition). ing.

JP 2007-079413 A

  However, the technique of Patent Document 1 has a problem that the acoustic signal after suppression of a predetermined component is in a monaural format. Similar problems can occur when emphasizing the localization component. In view of the above circumstances, an object of the present invention is to generate a stereo-type acoustic signal in which a localization component is emphasized or suppressed.

  In order to solve the above-described problems, an acoustic processing device according to the present invention includes a sum component generating unit that generates a sum component by adding a stereo first acoustic signal and a second acoustic signal, and a localization component at a specific position. Sum component of difference component generating means for generating a suppressed difference component by subtraction between the first acoustic signal and the second acoustic signal, and a processing coefficient sequence that is composed of coefficient values for each frequency and emphasizes or suppresses the localization component And coefficient sequence generation means for generating the difference component, and signal processing means for causing each coefficient value of the processing coefficient sequence to act on each frequency component of the first acoustic signal and the second acoustic signal. In the above configuration, since the processing coefficient sequence generated from the sum component and difference component of the first acoustic signal and the second acoustic signal is applied to each frequency component of the first acoustic signal and the second acoustic signal, It is possible to generate a stereo-type acoustic signal in which the localization component is emphasized or suppressed.

  In a preferred aspect of the present invention, the coefficient sequence generation means generates a processing coefficient sequence according to a result of subtracting the other spectrum from one spectrum of the sum component and the difference component. In the above aspect, a spectrum in which the localization component is emphasized or suppressed with high accuracy is generated by subtracting the other spectrum from one spectrum of the sum component and difference component, so that the localization component is effectively emphasized or suppressed. There is an advantage that the obtained processing coefficient sequence can be generated.

  The sound processing apparatus according to a preferred aspect of the present invention includes a variable setting unit that variably sets a localization variable indicating a specific position, and the difference component generation unit has a ratio according to the localization variable set by the variable setting unit. The other is subtracted from one of the first acoustic signal and the second acoustic signal. In the above aspect, the ratio of the first acoustic signal and the second acoustic signal at the time of subtraction by the difference component generation means is variably set according to the localization variable. Therefore, there is an advantage that the position (direction) of the localization component to be emphasized or suppressed can be variably controlled (not limited to the central direction).

  In a preferred aspect of the present invention, the coefficient sequence generation means includes first generation means for generating a first processing coefficient sequence corresponding to one of localization component enhancement and suppression from a sum component and a difference component, localization component enhancement and Second generation means for generating a second processing coefficient sequence corresponding to the other of the suppressions by subtracting each coefficient value of the first processing coefficient sequence from a predetermined value. In the above aspect, it is possible to generate processing coefficient sequences for emphasizing and suppressing localization components. Further, since the second processing coefficient sequence is generated by subtracting each coefficient value of the first processing coefficient sequence generated using the sum component and the difference component from the predetermined value, the first processing coefficient sequence and the second processing coefficient sequence Compared with the case where both of the processing coefficient sequences are generated directly from the sum component and the difference component, there is an advantage that the processing load by the coefficient sequence generation means is reduced.

  In a preferred aspect of the present invention, the coefficient sequence generation means changes the coefficient values of the processing coefficient sequence to either the first value or the second value depending on whether the coefficient value exceeds a threshold value. Including adjustment means. In the above aspect, since each coefficient value of the processing coefficient sequence is adjusted according to the relationship with the threshold value, the characteristics of the processing coefficient sequence (for example, a range to be emphasized or suppressed with respect to the target direction) ) Can be appropriately set according to the threshold value.

  The acoustic processing device according to each of the above aspects is realized by hardware (electronic circuit) such as a DSP (Digital Signal Processor) dedicated to processing of an acoustic signal, or a general-purpose calculation such as a CPU (Central Processing Unit). It is also realized by cooperation between the processing device and a program (software). The program of the present invention includes a sum component generation process for generating a sum component by adding a stereo-type first acoustic signal and a second acoustic signal, and a difference component obtained by suppressing a localization component at a specific position as a first acoustic signal and a first acoustic signal. Difference component generation processing generated by subtraction between two acoustic signals, and coefficient sequence generation processing for generating a processing coefficient sequence composed of coefficient values for each frequency and emphasizing or suppressing a localization component from a sum component and a difference component And causing the computer to execute signal processing in which each coefficient value of the processing coefficient sequence is applied to each frequency component of each of the first acoustic signal and the second acoustic signal. According to the above program, the same operation and effect as the sound processing apparatus of the present invention are realized. The program of the present invention is provided to a user in a form stored in a computer-readable recording medium and installed in the computer, or provided from a server device in a form of distribution via a communication network and installed in the computer. Is done.

1 is a block diagram of a sound processing apparatus according to a first embodiment. It is a block diagram of a coefficient setting part. It is a block diagram of the coefficient sequence production | generation part in 2nd Embodiment. It is explanatory drawing of operation | movement of a coefficient adjustment part. It is explanatory drawing of operation | movement of a coefficient adjustment part.

<A: First Embodiment>
FIG. 1 is a block diagram of a sound processing apparatus 100 according to the first embodiment of the present invention. A signal supply device 12, a sound emission device 14, and an input device 16 are connected to the sound processing device 100. The signal supply device 12 supplies the sound processing device 100 with time-domain sound signals SIN (SIN_L, SIN_R) representing the waveform of sound (speech and music). The sound signal SIN_L of the left channel and the sound signal SIN_R of the right channel are localized at positions where the sound images of a plurality of sound sources generating sound are different (that is, the sound amplitude and phase differ depending on the position of each sound source). In this way, a stereo signal is collected or processed. A sound collection device (stereo microphone) that collects ambient sound to generate an acoustic signal SIN, a playback device that acquires the acoustic signal SIN from a portable or built-in recording medium, and outputs it to the acoustic processing device 100; A communication device that receives the acoustic signal SIN from the communication network and outputs the acoustic signal SIN to the acoustic processing device 100 may be employed as the signal supply device 12.

  The acoustic processing device 100 generates an acoustic signal SOUT (SOUT_L, SOUT_R) from the acoustic signal SIN supplied by the signal supply device 12. The left-channel acoustic signal SOUT_L and the right-channel acoustic signal SOUT_R are stereo signals in which a localization component in which a sound image is localized at a target position is emphasized or suppressed among the sounds represented by the acoustic signal SIN. The sound emitting device 14 (for example, a stereo speaker or a stereo headphone) emits a sound wave corresponding to the acoustic signal SOUT (SOUT_L, SOUT_R) generated by the acoustic processing device 100.

  The input device 16 is a device (for example, a mouse or a keyboard) for a user to input an instruction to the sound processing device 100. By appropriately operating the input device 16, the user can arbitrarily instruct the acoustic processing device 100 to perform either the localization component position (direction) or the localization component enhancement / suppression processing. It is.

  As shown in FIG. 1, the sound processing device 100 is realized by a computer system including an arithmetic processing device 22 and a storage device 24. The storage device 24 stores a program PG executed by the arithmetic processing device 22 and data used by the arithmetic processing device 22. A known recording medium such as a semiconductor recording medium or a magnetic recording medium or a combination of a plurality of types of recording media is arbitrarily adopted as the storage device 24. A configuration in which the acoustic signal SIN (SIN_L, SIN_R) is stored in the storage device 24 (therefore, the signal supply device 12 can be omitted) is also suitable.

  The arithmetic processing unit 22 executes a program PG stored in the storage device 24 to thereby generate a plurality of functions (variable setting unit 32, frequency analysis unit 34, coefficient setting unit) for generating the acoustic signal SOUT from the acoustic signal SIN. 36, a signal processing unit 38, and a waveform synthesis unit 40). A configuration in which each function of the arithmetic processing unit 22 is distributed over a plurality of integrated circuits, or a configuration in which a dedicated electronic circuit (DSP) realizes each function may be employed.

  The variable setting unit 32 sets the localization variable α to be variable. The localization variable α is a variable that designates the position (direction) of the sound image of the localization component. The variable setting unit 32 of the present embodiment variably sets the localization variable α (0 ≦ α ≦ 1) in accordance with an instruction from the user to the input device 16. For example, when the localization variable α is 0.5 (median value), the center (front) direction is indicated. Further, as the localization variable α is closer to 1, a rightward direction is indicated, and as the localization variable α is closer to 0, a leftward direction is indicated. The user can change the localization variable α by operating the input device 16 at any time while listening to the reproduced sound from the sound emitting device 14.

The frequency analysis unit 34 sequentially generates a frequency spectrum (complex spectrum) LA of the acoustic signal SIN_L and a frequency spectrum (complex spectrum) RA of the acoustic signal SIN_R for each unit section (frame) on the time axis. The frequency spectrum LA is a series of frequency components LAk (e ^jω ) (LA1 (e ^jω ) to LAK (e ^jω )) corresponding to each of K frequencies (frequency bands) f1 to fK (k = 1 to 1). K). The symbol j means an imaginary unit. Similarly, the frequency spectrum RA is a series of frequency components RAk (e ^jω ) (RA1 (e ^jω ) to RAK (e ^jω )) corresponding to each of the frequencies f1 to fK. For the generation of the frequency spectrum LA and the frequency spectrum RA, a known frequency analysis such as a short-time Fourier transform may be arbitrarily employed. A filter bank composed of K band pass filters having different pass bands can also be adopted as the frequency analysis unit 34.

  The coefficient setting unit 36 in FIG. 1 includes a processing coefficient sequence Ge for enhancing the localization component of the acoustic signal SIN (SIN_L, SIN_R) and a processing coefficient sequence for suppressing the localization component of the acoustic signal SIN. Gs. The processing coefficient sequence Ge and the processing coefficient sequence Gs are sequentially generated for each unit section using the frequency spectrum LA and the frequency spectrum RA. The processing coefficient sequence Ge is a series of coefficient values Ge [k] (Ge [1] to Ge [K]) corresponding to each of the frequencies f1 to fK, and the processing coefficient sequence Gs is assigned to each of the frequencies f1 to fK. This is a series of corresponding coefficient values Gs [k] (Gs [1] to Gs [K]).

The coefficient value Ge [k] and the coefficient value Gs [k] correspond to a gain (spectral gain) with respect to the frequency component LAk (e ^jω ) of the acoustic signal SIN_L and the frequency component RAk (e ^jω ) of the acoustic signal SIN_R. It is variably set within the range of 0 or more and 1 or less according to the characteristics of SIN (SIN_L, SIN_R) (0 ≦ Ge [k] ≦ 1, 0 ≦ Gs [k] ≦ 1). Specifically, the coefficient values Ge [1] to Ge [K] of the processing coefficient sequence Ge for emphasizing the localization component are set to 1 as the coefficient value Ge [k] of the frequency fk having a large localization component power (amplitude). Set to a close number. On the other hand, the coefficient values Gs [1] to Gs [K] of the processing coefficient sequence Gs for suppressing the localization component are set to values closer to 0 as the coefficient value Gs [k] of the frequency fk having a larger localization component power. .

The signal processing unit 38 of FIG. 1 causes the processing coefficient sequence Ge or the processing coefficient sequence Gs generated by the coefficient setting unit 36 to individually act (typically multiply) each of the frequency spectrum LA and the frequency spectrum RA. The frequency spectrum LB and the frequency spectrum RB are sequentially generated for each unit section. The frequency spectrum LB is a series of frequency components LBk (e ^jω ) (LB1 (e ^jω ) to LBK (e ^jω )) corresponding to each of the frequencies f1 to fK, and the frequency spectrum RB is each of the frequencies f1 to fK. Is a series of frequency components RBk (e ^jω ) corresponding to (RB1 (e ^jω ) to RBK (e ^jω )). The frequency spectrum LA and the frequency spectrum RA of each unit section are multiplied by the processing coefficient sequence Ge or the processing coefficient sequence Gs generated by the coefficient setting unit 36 for the unit section.

When the user instructs the input device 16 to emphasize the localization component, the signal processing unit 38 processes the frequency spectrum LA and the frequency spectrum RA as shown in the following formulas (1a) and (1b). A frequency spectrum LB and a frequency spectrum RB are generated by multiplication of the coefficient sequence Ge. That is, the frequency components LBk of each frequency fk in the frequency spectrum ^LB (e jω) is set to the multiplication value between the frequency component of the frequency fk LAk ^(e jω) and the coefficient value Ge [k] (Formula (1a)) , the frequency components RBk of each frequency fk in the frequency spectrum ^RB (e jω) is set to the multiplication value between the frequency component of the frequency fk RAk ^(e jω) and the coefficient value Ge [k] (equation (1b)) . Therefore, the frequency spectrum LB and the frequency spectrum RB in which the localization component of the acoustic signal SIN (SIN_L, SIN_R) is emphasized are generated.

On the other hand, when the user instructs the input device 16 to suppress the localization component, the signal processing unit 38, as shown in the following equations (2a) and (2b), the frequency spectrum LB and the frequency spectrum RB The processing coefficient sequence Gs for suppressing the localization component is applied to the generation of. That is, each frequency component LBk (e ^jω ) of the frequency spectrum LB is calculated by multiplying each frequency component LAk (e ^jω ) of the frequency spectrum LA by each coefficient value Gs [k] of the processing coefficient sequence Gs (formula (2a )), calculates the respective frequency components of the frequency spectrum RB RBk ^(e jω) by multiplying the each frequency component RAk of the frequency spectrum RA (e ^{j [omega])} and the coefficient value Gs [k] (formula (2b)). Therefore, the frequency spectrum LB and the frequency spectrum RB in which the localization component of the acoustic signal SIN (SIN_L, SIN_R) is suppressed are generated.

  The waveform synthesizer 40 in FIG. 1 generates a stereo acoustic signal SOUT_L and an acoustic signal SOUT_R from the frequency spectrum LB and the frequency spectrum RB processed by the signal processor 38. Specifically, the waveform synthesizer 40 generates the acoustic signal SOUT_L by converting the frequency spectrum LB for each unit section into a time domain signal by inverse Fourier transform and connecting the preceding and following unit sections to each other. Similarly, the waveform synthesizer 40 generates an acoustic signal SOUT_R from each frequency spectrum RB. The acoustic signals SOUT (SOUT_L, SOUT_R) generated by the waveform synthesis unit 40 are supplied to the sound emitting device 14 and reproduced as sound waves.

Next, details of the coefficient setting unit 36 will be described. FIG. 2 is a block diagram of the coefficient setting unit 36. As shown in FIG. 2, the coefficient setting unit 36 includes a sum component generation unit 52, a difference component generation unit 54, and a coefficient sequence generation unit 60. The sum component generation unit 52 adds the frequency components LA1 (e ^jω ) to LAK (e ^jω ) of the acoustic signal SIN_L and the frequency components RA1 (e ^jω ) to RAK (e ^jω ) of the acoustic signal SIN_R for each unit interval. A sum component (complex spectrum) M is sequentially generated. The sum component M is a series of frequency components Mk (e ^jω ) (M1 (e ^jω ) to MK (e ^jω )) corresponding to each of the frequencies f1 to fK. As shown in Equation (3), the frequency component Mk (e ^jω ) of the frequency fk of the sum component M is the addition (complex number) of the frequency component LAk (e ^jω ) and the frequency component RAk (e ^jω ) of the frequency fk. It corresponds to. Therefore, the sum component M corresponds to a monaural signal in which sounds from all sound sources are mixed. A configuration in which a weighted sum or average of the frequency component LAk (e ^jω ) and the frequency component RAk (e ^jω ) is calculated as the sum component M may be employed.

2 performs subtraction between the frequency components LA1 (e ^jω ) to LAK (e ^jω ) of the acoustic signal SIN_L and the frequency components RA1 (e ^jω ) to RAK (e ^jω ) of the acoustic signal SIN_R. Thus, a difference component (complex spectrum) S is sequentially generated for each unit interval. The difference component S is a series of frequency components Sk (e ^jω ) (S1 (e ^jω ) to SK (e ^jω )) corresponding to each of the frequencies f1 to fK. The difference component generator 54 calculates the frequency components S1 (e ^jω ) to SK (e ^jω ) by the calculation (weighted subtraction) of Expression (4) using the localization variable α set by the variable setting unit 32.

As it is understood from the formula (4), varying proportions frequency components at (weight value) LAk (e ^{j [omega])} from a frequency component RAk (e ^{j [omega])} subtraction (reverse phase addition) according to the localization variable α Thus, each frequency component Sk (e ^jω ) of the difference component S is generated. Therefore, the difference component S is a signal in which the localization component in the position (direction) corresponding to the localization variable α in the acoustic signal SIN (SIN_L, SIN_R) is relatively suppressed with respect to other components (that is, other than the localization component). Signal with relatively emphasized components). For example, when the localization variable α is 0.5 (median value), a difference component S in which a localization component in the center direction (that is, a component having substantially the same amplitude and phase) is suppressed is generated. Further, as the localization variable α exceeds 0.5, the localization component closer to the center direction is suppressed by the difference component S, and as the localization variable α is less than 0.5, the localization component toward the left side relative to the center direction is suppressed. However, the difference component S is suppressed.

The symbol max (α, 1-α) in Equation (4) means the maximum value of the localization variable α or the variable (1-α). Since the localization variable α is set to a numerical value of 1 or less, there is a possibility that the power (amplitude) of the frequency component Sk (e ^jω ) is insufficient only by the calculation of the numerator of Equation (4). Dividing by the maximum value max (α, 1-α) as in Equation (4) is equivalent to the power of the frequency component Sk (e ^jω ) and the frequency component LAk (e ^jω ) or frequency component RAk (e ^jω ). It is for maintaining.

  2 uses the sum component M generated by the sum component generation unit 52 and the difference component S generated by the difference component generation unit 54 to process the localization component enhancement processing coefficient sequence Ge (Ge [1] to Ge [K]) and a processing coefficient sequence Gs (Gs [1] to Gs [K]) for suppressing the localization component are generated. As shown in FIG. 2, the coefficient sequence generation unit 60 includes a first generation unit 62 that generates a processing coefficient sequence Ge and a second generation unit 64 that generates a processing coefficient sequence Gs.

The first generation unit 62 calculates each coefficient value Ge [k] of the processing coefficient sequence Ge by the calculation of the following formula (5).

The symbol P [k] in Equation (5) means the power at the frequency fk in the power spectrum P in which the localization component is emphasized. The power P [k] is calculated by, for example, the following formula (6a) and formula (6b).

As is understood from the formula (6a), the power of the frequency component ^{Mk (e jω) | Mk (} e jω) | 2 is the power of the frequency component ^{Sk (e jω) | Sk (} e jω) | 2 over the frequency fk The power P [k] is set to a value obtained by subtracting the power | Sk (e ^jω ) | ² of the difference component S from the power | Mk (e ^jω ) | ² of the sum component M. That is, the power spectrum P is generated by subtraction (spectrum subtraction) between the power spectrum of the sum component M and the power spectrum of the difference component S. On the other hand, the power ^| Mk (e jω) | ² is the power ^| Sk (e jω) | Power P [k] of ² or less and comprising a frequency fk, the power of the sum component ^{M | Mk (e jω) |} 2 a predetermined Is set to a multiplication value of the coefficient (flooring coefficient) β. As can be understood from the above description, the calculations of Equation (6a) and Equation (6b) are performed when the sum component M is assumed to be a signal component (target sound) and the difference component S is assumed to be a noise component. This corresponds to spectral subtraction (SS).

Since the frequency component Sk (e ^jω ) is a component in which the localization component is suppressed, the series of powers P [1] to P [K] calculated by the equations (6a) and (6b) is the acoustic signal SIN (SIN_L , SIN_R), the power spectrum P of the component emphasizing the localization component. Therefore, the numerator of Expression (5) corresponds to the amplitude of the component in which the localization component is emphasized. Note that dividing the amplitude (P [k]) ^1/2 by the amplitude | Mk (e ^jω ) | of the frequency component Mk (e ^jω ) | in the equation (5) ^reduces the coefficient value Ge [k] to 1 or less. This is for normalization to the numerical value of (0 ≦ Ge [k] ≦ 1).

  As understood from the above description, the coefficient values Ge [1] to Ge [K] of the processing coefficient sequence Ge generated by the first generation unit 62 are the power (amplitude) of the localization component at the position corresponding to the localization variable α. ) Is a value closer to 1 as the coefficient value Ge [k] of the frequency fk is larger, and is closer to 0 as the coefficient value Ge [k] of the frequency fk whose power of the localization component is smaller. Therefore, the signal processing unit 38 multiplies each of the frequency spectrum LA and the frequency spectrum RA by the processing coefficient sequence Ge to generate the stereo-type acoustic signal SOUT (SOUT_L, SOUT_R) with the localization component emphasized as described above. The

The second generation unit 64 generates a processing coefficient sequence Gs (coefficient values Gs [1] to Gs [K]) for suppressing the localization component using the processing coefficient sequence Ge generated by the first generation unit 62. Specifically, as shown in Equation (7), the second generation unit 64 subtracts each coefficient value Ge [k] of the processing coefficient sequence Ge from a predetermined value (1 in the present embodiment) to thereby process the processing coefficient sequence. Each coefficient value Gs [k] of Gs is calculated.

  As understood from the equation (7), the coefficient values Gs [1] to Gs [K] of the processing coefficient sequence Gs generated by the second generation unit 64 are the power of the localization component at the position according to the localization variable α ( The coefficient value Gs [k] of the frequency fk having a larger amplitude) is closer to 0, and the coefficient value Gs [k] of the frequency fk having a smaller localization component power is closer to 1. Accordingly, the signal processing unit 38 multiplies each of the frequency spectrum LA and the frequency spectrum RA by the processing coefficient sequence Gs, thereby generating the stereo-type acoustic signal SOUT (SOUT_L, SOUT_R) in which the localization component is suppressed as described above. The

  As described above, in the first embodiment, each of the acoustic signal SIN_L (frequency spectrum LA) and the acoustic signal SIN_R (frequency spectrum RA) is individually multiplied by the processing coefficient sequence Gs or the processing coefficient sequence Ge. Therefore, the acoustic signal SOUT (SOUT_L, SOUT_R) in which the localization component is emphasized or suppressed can be generated in the stereo format.

  By the way, in Japanese Patent No. 3670562, either an attenuation coefficient gi (k) corresponding to the amplitude ratio between channels of a stereo signal or an attenuation coefficient gp (k) corresponding to a phase difference is selected and each channel is selected. A configuration for multiplying an acoustic signal is disclosed. However, in the above technique, the attenuation coefficient gi (k) according to the amplitude ratio and the attenuation coefficient gp (k) according to the phase difference are alternatively applied. If they are different, there is a problem that it is difficult to properly emphasize or suppress the localization component. On the other hand, in the first embodiment, the sum component M and the difference component S calculated as a complex spectrum from the acoustic signal SIN_L (frequency spectrum LA) and the acoustic signal SIN_R (frequency spectrum RA) are processed coefficient sequence Ge and processing coefficient sequence Gs. Therefore, the processing coefficient sequence Ge and the processing coefficient sequence Gs reflecting both the amplitude difference and the phase difference between the acoustic signal SIN_L and the acoustic signal SIN_R are generated. Therefore, in addition to the case where only one of the amplitude and the phase is different between the acoustic signal SIN_L and the acoustic signal SIN_R, the localization component can be effectively enhanced or suppressed when both the amplitude and the phase are different. The effect of is realized.

<B: Second Embodiment>
A second embodiment of the present invention will be described. In the following examples, elements having the same functions and functions as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and detailed descriptions thereof are appropriately omitted.

  FIG. 3 is a block diagram of the coefficient string generation unit 60 of the second embodiment. As shown in FIG. 3, the coefficient sequence generation unit 60 of the second embodiment includes a coefficient adjustment unit 66 in addition to the first generation unit 62 and the second generation unit 64 similar to those of the first embodiment. . The coefficient adjustment unit 66 generates a processing coefficient sequence GeA (coefficient values GeA [1] to GeA [K]) by adjusting each coefficient value Ge [k] of the processing coefficient sequence Ge generated by the first generation unit 62, A processing coefficient sequence GsA (coefficient values GsA [1] to GsA [K]) is generated by adjusting each coefficient value Gs [k] of the processing coefficient sequence Gs generated by the second generation unit 64.

  Part (A) of FIG. 4 is a coefficient value Gs [k] corresponding to the frequency fk of the component in which the sound image is localized in the central direction (α = 0.5) in the processing coefficient sequence Gs generated by the second generation unit 64. It is a graph which shows the relationship between (vertical axis) and localization variable (alpha) (horizontal axis). As understood from part (A) of FIG. 4, the relationship of the processing coefficient sequence Gs is such that the coefficient value Gs [k] becomes a value closer to 0 as the localization variable α is closer to 0.5 (center direction). The numerical value Gs [k] changes linearly according to the localization variable α.

  Part (B) of FIG. 4 is a graph showing the relationship between the coefficient value GsA [k] (vertical axis) and the localization variable α (horizontal axis) of the processing coefficient sequence GsA after adjustment by the coefficient adjustment unit 66. As shown in part (B) of FIG. 4, when the coefficient value Gs [k] of the processing coefficient sequence Gs exceeds the threshold value Gs_TH, the coefficient adjustment unit 66 sets the adjusted coefficient value GsA [k] to a predetermined value. When the coefficient value Gs [k] is lower than the threshold value Gs_TH, the coefficient value GsA [k] is set to a predetermined value Gs_min.

The predetermined value Gs_max is set to 1, for example, and the predetermined value Gs_min is set to 0, for example. Therefore, when the localization variable α is set within a predetermined range A including a numerical value (0.5) corresponding to the center direction, the frequency component LAk (is multiplied by the predetermined value Gs_min (GsA [k] = 0). e ^jω ) and frequency component RAk (e ^jω ) are suppressed (removed), and when the localization variable α is set to a value outside the range A, multiplication by a predetermined value Gs_max (GsA [k] = 1) The frequency component LAk (e ^jω ) and the frequency component RAk (e ^jω ) are maintained.

  Although the adjustment of the processing coefficient sequence Gs has been exemplified above, the enhancement processing coefficient sequence Ge is also adjusted by the same method. That is, as shown in part (A) and part (B) of FIG. 5, the coefficient adjustment unit 66 adjusts the coefficient value after adjustment when the coefficient value Ge [k] of the processing coefficient sequence Ge exceeds the threshold value Ge_TH. GeA [k] is set to a predetermined value Ge_max (for example, 1), and when the coefficient value Ge [k] is lower than the threshold value Ge_TH, the coefficient value GeA [k] is set to a predetermined value Ge_min (for example, 0). The signal processing unit 38 generates the frequency spectrum LB and the frequency spectrum RB by applying the processing coefficient sequence GeA or the processing coefficient sequence GsA processed by the coefficient adjusting unit 66 to the frequency spectrum LA and the frequency spectrum RA.

  The threshold value Ge_TH and the threshold value Gs_TH are variably set according to an instruction from the user to the input device 16, for example. The range of the localization variable α in which the localization component is emphasized / suppressed changes according to the threshold value Ge_TH and the threshold value Gs_TH. That is, the larger the threshold value Ge_TH, the narrower the range of the localization variable α in which the localization component is emphasized, and the larger the threshold value Gs_TH, the wider the range of the localization variable α in which the localization component is emphasized.

  In the second embodiment, the same effect as in the first embodiment is realized. In the second embodiment, the coefficient value Gs [k] is adjusted to the coefficient value GsA [k] (Gs_max, Gs_min), and the coefficient value Ge [k] is changed to the coefficient value GeA [k] (Ge_max, Ge_min). Since it is adjusted, it is possible to clearly define the range of the localization variable α from which the localization component is removed.

<C: Modification>
Each of the above forms can be variously modified. Specific modifications are exemplified below. Two or more aspects arbitrarily selected from the following examples can be appropriately combined.

(1) Modification 1
In each of the above embodiments, as understood from the equation (4), the ratio of the amplitude of the acoustic signal SIN_L (frequency component LAk (e ^jω )) and the acoustic signal SIN_R (frequency component RAk (e ^jω )) is a localization variable. Although the difference component S is calculated so as to change linearly according to α, as illustrated in the following embodiments, the calculation method of the sum component M and the difference component S and the relationship with the localization variable α are appropriately determined. Be changed.

<First aspect>
^LAk (e jω) | | ² and the power of the acoustic signal ^SIN_R | RAk (e jω) | power of the acoustic signal SIN_L configured to calculate the ² from the sum component M and the difference component S may be employed. Specifically, the sum component generation unit 52 generates the sum component M (complex spectrum composed of frequency components M1 (e ^jω ) to MK (e ^jω )) by the calculation of the following formula (8a), and the difference The component generation unit 54 generates a difference component S (a complex spectrum composed of frequency components S1 (e ^jω ) to SK (e ^jω )) by calculation of the following formula (8b). Therefore, in the difference component S, the power ratio between the acoustic signal SIN_L and the acoustic signal SIN_R changes linearly according to the localization variable α. Symbols e ^jL in equation (8a) and Equation (8b) denotes the phase of the frequency spectrum LA, symbol e ^jR means the phase of the frequency spectrum RA.

When the sum component M and the difference component S are generated by the above method, the first generation unit 62 of the coefficient sequence generation unit 60 generates a power spectrum P (power P [k]) in which the localization component is emphasized by the following formula ( The coefficient values Ge [k] of the processing coefficient sequence Ge are calculated by the calculation of the formula (10) using the power spectrum P, which is generated by the calculations of 9a) and (9b). The method by which the second generation unit 64 generates the processing coefficient sequence Gs from the processing coefficient sequence Ge is the same as in the first embodiment (Formula (7)). With the above configuration, the same effect as that of the first embodiment is realized.

<Second aspect>
A configuration in which the position (direction) of the localization component is controlled according to the function f (α) of the localization variable α can be adopted. Specifically, the sum component generation unit 52 generates the sum component M (frequency components M1 (e ^jω ) to MK (e ^jω )) by the calculation of the following formula (11a), and the difference component generation unit 54 The difference component S (frequency components S1 (e ^jω ) to SK (e ^jω )) is generated by the calculation of the following formula (11b). Therefore, the ratio of the amplitudes of the acoustic signal SIN_L and the acoustic signal SIN_R in the difference component S changes according to the function f (α) of the localization variable α. The coefficient sequence generation unit 60 uses the same method as in the first embodiment (Formula (5), Formula (6a), Formula (6b), Formula (7)), and the sum component M of Formula (11a) and Formula (11b) The processing coefficient sequence Ge and the processing coefficient sequence Gs are calculated from the difference component S).

In Equation (6a), the difference between the power of the sum component M | Mk (e ^jω ) | ² and the power of the difference component S | Sk (e ^jω ) | ² is calculated as the power P [k]. As shown in the equation (6c), a configuration is also employed in which the difference between the amplitude | Mk (e ^jω ) | of the sum component M and the amplitude | Sk (e ^jω ) | of the difference component S is calculated as the amplitude P [k]. obtain. In the configuration in which the amplitude P [k] is calculated using the equation (6c), the first generation unit 62 calculates the coefficient value Ge [k] of the processing coefficient sequence Ge by the calculation of the equation (5a).

(2) Modification 2
In each of the above embodiments, the processing coefficient sequence Ge is calculated by subtraction of the power spectrum (Formula (6a), Formula (9a)) or subtraction of the amplitude spectrum (Formula (6c)). Is optional. For example, if the localization component included in the sum component M is assumed to be a signal component and the difference component S is assumed to be a noise component, the generation of the processing coefficient sequence Ge using the sum component M and the difference component S may include a noise component (difference). A known speech enhancement technique for generating a numerical sequence (processing coefficient sequence Ge) for emphasizing a signal component (localization component) by suppressing the component S) can be similarly applied.

  Examples of technologies that can be applied to the generation of the processing coefficient sequence Ge include speech enhancement using a Wiener filter and speech enhancement using an MMSE-STSA method or a MAP (maximum a posteriori estimation) estimation method. Can be done. For the MMSE-STSA method, see Y. Ephraim and D. Malah, "Speech enhancement using a minimum mean-square error short-time spectral amplitude estimator", IEEE ASSP, vol.ASSP-32, no.6, p.1109- 1121, Dec. 1984, MAP estimation method is described in T. Lotter and P. Vary, "Speech enhancement by MAP spectral amplitude estimation using a Super-Gaussian speech model", EURASIP Journal on Applied Signal Processing, vol.2005 , no, 7, p.1110-1126, July 2005.

(3) Modification 3
In each of the above embodiments, the processing coefficient sequence Gs is generated by the calculation (Formula (7)) using the processing coefficient sequence Ge. However, the coefficient sequence generation unit 60 performs the sum component M in the same manner as the generation of the processing coefficient sequence Ge. A configuration in which the processing coefficient sequence Gs is directly generated from the difference component S can also be adopted. Specifically, when the sum component M and the difference component S in each of the above-exemplified formulas are replaced with each other to generate the processing coefficient sequence Ge, the processing coefficient sequence Gs for suppressing the localization component can be generated. It is.

  However, according to the configuration of the first embodiment in which the processing coefficient sequence Gs is calculated using the processing coefficient sequence Ge, processing for directly calculating the processing coefficient sequence Gs from the sum component M and the difference component S is not necessary. . Therefore, there is an advantage that the processing load by the coefficient sequence generator 60 is reduced. A processing coefficient sequence Gs is directly generated from the sum component M and the difference component S, and each coefficient value Gs [k] of the processing coefficient sequence Gs is subtracted from a predetermined value (for example, 1) in the same manner as the equation (7). Thus, a configuration for generating the processing coefficient sequence Ge (coefficient value Ge [k]) may be employed.

(4) Modification 4
In each of the above embodiments, the processing coefficient sequence G (Ge, Gs) is generated for each unit section, but the generation cycle of the processing coefficient sequence G is arbitrary. For example, a configuration in which the signal processing unit 38 applies the processing coefficient sequence G sequentially generated by the coefficient sequence generation unit 60 with a set of a predetermined number of unit intervals as a cycle may be adopted for a plurality of unit intervals in the cycle. In each of the above embodiments, the processing coefficient sequence G generated for each unit section is applied to the processing of the frequency spectrum (LA, RA) of the unit section. However, the processing coefficient sequence G of each unit section is used as the unit section. A configuration applied to the processing of the frequency spectrum (LA, RA) of each unit section after elapse of time can also be adopted.

(5) Modification 5
In each of the above embodiments, the processing coefficient sequence G (Ge, Gs) is multiplied by the frequency spectrum (LA, RA) of the acoustic signal SIN, but the content of processing by the signal processing unit 38 is appropriately changed. For example, a configuration in which the acoustic signal SOUT (SOUT_L, SOUT_R) is generated by subtracting the processing coefficient sequence G (Ge, Gs) from the frequency component LAk (e ^jω ) and the frequency component RAk (e ^jω ) may be employed. In contrast to the processing coefficient sequence Ge of the first embodiment, the processing coefficient sequence Ge for emphasis in the above configuration is set to a value closer to 0 as the coefficient value Ge [k] of the frequency fk where the power of the localization component is large. The The same applies to the processing coefficient sequence Gs for suppression. Contrary to the processing coefficient sequence Gs of the first embodiment, the coefficient value Gs [k] of the frequency fk having a large localization component power is set to a value closer to 1. The

(6) Modification 6
A configuration in which the localization component is emphasized / suppressed by limiting to components within a predetermined frequency band is also preferable. For example, the processing in each of the above modes is executed only for the frequency band (for example, 100 kHz to 8 kHz) in which the power of human voice is concentrated in the acoustic signal SIN (reproduction is performed without processing for other bands).

(7) Modification 7
In each of the above embodiments, the coefficient sequence generation unit 60 generates both the processing coefficient sequence Ge for emphasizing the localization component and the processing coefficient sequence Gs for suppression, but the coefficient sequence generation unit 60 generates the processing coefficient sequence Ge and the processing coefficient. A configuration that generates only one of the columns Gs may also be employed. Therefore, for example, the second generation unit 64 in each of the above forms can be omitted.

(8) Modification 8
A configuration in which the coefficient β (Equation (6b), Equation (9b)) in each of the above embodiments is variably set according to an instruction from the user to the input device 16, for example, is also suitable. As the coefficient β is smaller (closer to 0), the degree of suppression of the localization component is strengthened and the degree of enhancement of the localization component is reduced. When the coefficient β is large, the coefficient value Gs [k] of most of the frequencies fk other than the localization component in the processing coefficient sequence Gs for suppression becomes a sufficiently small value, so that the acoustic signal SOUT (SOUT_L, SOUT_R) may be insufficient. Therefore, when the localization component is suppressed by setting the coefficient β to a large numerical value, a configuration in which the volume of the acoustic signal SOUT is increased is preferable. Similarly, when the coefficient β is small, the coefficient value Ge [k] of most of the frequencies fk in the emphasis processing coefficient string Ge can be a sufficiently small numerical value. When emphasizing the component, a configuration that increases the volume of the acoustic signal SOUT is preferably employed.

DESCRIPTION OF SYMBOLS 100 ... Sound processing device, 12 ... Signal supply device, 14 ... Sound emission device, 16 ... Input device, 22 ... Arithmetic processing device, 24 ... Memory | storage device, 32 ... Variable setting part, 34 ... Frequency analysis unit 36... Coefficient setting unit 38... Signal processing unit 40... Waveform synthesis unit 52 52 Sum component generation unit 54. Difference component generation unit 60 60 Coefficient sequence generation unit 62 ... First generation unit, 64... Second generation unit, 66.

Claims (6)

Sum component generating means for generating a sum component by adding the first acoustic signal and the second acoustic signal in stereo format;
Difference component generation means for generating a difference component in which a localization component at a specific position is suppressed by subtraction between the first acoustic signal and the second acoustic signal;
A coefficient sequence generation means configured to generate a processing coefficient sequence composed of coefficient values for each frequency and emphasizing or suppressing the localization component from the sum component and the difference component;
Signal processing means for causing each coefficient value of the processing coefficient sequence to act on each frequency component of each of the first acoustic signal and the second acoustic signal ;
The coefficient sequence generation means includes
First generation means for generating a first processing coefficient sequence corresponding to one of emphasis and suppression of the localization component from the sum component and the difference component;
And a second generation unit that generates a second processing coefficient sequence corresponding to the other of the localization component enhancement and suppression by subtracting each coefficient value of the first processing coefficient sequence from a predetermined value . The coefficient sequence generation means includes coefficient adjustment means for changing each coefficient value of the processing coefficient sequence to a first value or a second value depending on whether the coefficient value exceeds a threshold value.
The sound processing apparatus according to claim 1 . Sum component generating means for generating a sum component by adding the first acoustic signal and the second acoustic signal in stereo format;
Difference component generation means for generating a difference component in which a localization component at a specific position is suppressed by subtraction between the first acoustic signal and the second acoustic signal;
A coefficient sequence generation means configured to generate a processing coefficient sequence composed of coefficient values for each frequency and emphasizing or suppressing the localization component from the sum component and the difference component;
Signal processing means for causing each coefficient value of the processing coefficient sequence to act on each frequency component of each of the first acoustic signal and the second acoustic signal ;
The coefficient sequence generation means includes acoustic coefficient processing that includes coefficient adjustment means for changing each coefficient value of the processing coefficient sequence to either the first value or the second value depending on whether the coefficient value exceeds a threshold value. apparatus.   The coefficient sequence generation means variably sets the threshold value according to an instruction from a user.
  The sound processing apparatus according to claim 2 or 3. Comprising variable setting means for variably setting a localization variable indicating the specific position;
The difference component generation means subtracts the other from one of the first acoustic signal and the second acoustic signal at a ratio according to the localization variable set by the variable setting means.
The sound processing apparatus according to claim 1 .   The difference component generation means subtracts the other from one of the first acoustic signal and the second acoustic signal at a ratio according to the localization variable, and a numerical value obtained by subtracting the localization variable and the localization variable from a predetermined value. Divide by the maximum of and
  The sound processing apparatus according to claim 5.

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