JP2017130868A - Acoustic device and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acoustic device capable of preventing the "center missing" phenomenon where the vocals, localized in the center, sound lean.SOLUTION: Input signals of left and right channels are filtered by corresponding highpass filters 10,12 and inputted to a crosstalk cancellation processing section 410. The processed signal on one channel side is then filtered by a low shelving filter 40 (42), and the filtered signal is added to the signal on the other channel side filtered by a lowpass filter 20 (22). An operating section 60 obtains a control factor k for controlling a crosstalk cancellation amount, based on the input signals of the left and right channels. Each multiplication section 70, 72 multiplies the control factor k and the output signal from a FIR filter 30, 32 before being outputted to an adder 52, 52.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a device having a stereo sound expansion function, and more particularly, to an audio device that maintains the expansion function while allowing the amount of crosstalk cancellation to be controlled.

  As shown in FIG. 7, when a stereo signal composed of a left channel signal and a right channel signal is output from the left speaker 300 and the right speaker 310, if the two left and right speakers 300, 310 are close to each other, a wide stereo feeling is obtained. Although it cannot be obtained, the sound image of the stereo sound output from both speakers 300 and 310 can be expanded by applying the crosstalk cancellation process. The output sound of the left speaker 300 reaches the left ear Z1 and right ear Z2 of the listener M, and the output sound from the right speaker 310 also reaches the left ear Z1 and right ear Z2 of the listener M, as shown in the figure. In addition, four paths “G11, G12, G21, G22” where the output sounds from both speakers 300, 310 reach the ears Z1, Z2 of the listener M are made. Here, “crosstalk” is a path (G12, G21) in which the output sound from the left speaker 300 and the right speaker 310 reaches the far ear of the listener M.

By performing the crosstalk canceling process for canceling the crosstalk, the sound that the output sound of the left speaker 300 reaches the right ear Z2 is suppressed, so that the volume difference between the left ear Z1 and the right ear Z2 is reduced. The sound image is heard from the left direction, becoming larger than when it is not processed. As a result, it feels as if sound is being output from the virtual left speaker 305. Similarly, it is felt that the sound from the right speaker 310 is output from the virtual right speaker 315 by performing the crosstalk cancellation process.

  Patent Documents 1 and 2 disclose devices that perform sound image adjustment using crosstalk cancellation processing. The circuit described in Patent Document 1 is a crosstalk cancellation circuit that realizes localization of a sound image in a wide range, and delays and attenuates the tone of one channel of stereo to invert the phase, and outputs from the other channel. The circuit includes a control circuit that controls at least the attenuation amount according to the localization of a musical sound signal input in stereo (see, for example, Patent Document 1). That is, in this crosstalk cancellation circuit, the amount of cancellation is increased or decreased depending on the position of the musical sound, and a clear sense of localization is maintained.

  Further, according to the apparatus described in Patent Document 2, the sound field effect applying means generates a sound signal of two left and right channels by applying a three-dimensional sound field effect to the input sound signal, and further crosstalk. When the canceling means emits the sound signal of each channel from two speakers located in front of the listener, each cancels the sound signal so as to reach the left and right ears of the listener without causing crosstalk. By performing the arithmetic processing, the sound field effect corresponding to the three-dimensional acoustic space is obtained by only two speakers (for example, see Patent Document 2).

  FIG. 8A shows a configuration example of the crosstalk cancellation processing unit. According to the crosstalk cancellation processing unit 400, an input signal of the left channel (Lch) is received by each of an FIR (Finite Impulse Response) filter 100 and an FIR filter 110. Similarly, the right channel (Rch) input signal is filtered by each of the FIR filter 120 and the FIR filter 130. Then, the output signal of the FIR filter 100 and the output signal of the FIR filter 120 are added by the adder 200, and this added signal is output from the right speaker 310, while the output signal of the FIR filter 110 and the output signal of the FIR filter 130 are output. The output signal is added by the adder 210, and this added signal is output from the left speaker 300. Thereby, the path G21 and the path G12 are cancelled. The transfer functions of the FIR filter 100, the FIR filter 110, the FIR filter 120, and the FIR filter 130 are H11, H12, H21, and H22.

FIG. 8B shows a configuration example of the simplified crosstalk cancellation processing unit 410 in which the number of filters in the crosstalk cancellation processing unit 400 in FIG. The adder 202 adds the input signal of the left channel (Lch) and the signal obtained by filtering the input signal of the right channel (Rch) by the FIR filter 120, and the addition signal is output from the right speaker 310. Similarly, the adder 212 adds the input signal of the right channel (Rch) and the signal obtained by filtering the input signal of the left channel (Lch) by the FIR filter 110, and this addition signal is output from the left speaker 300. .

Even this simple crosstalk cancellation circuit 410 can suppress the crosstalk components (G12, G21). When the transfer function of each filter in FIG. 8A is divided by, for example, H11, the transfer function of each FIR filter 100, 110, 120, 130 is “1, (H12 / H11), (H21 / H11), 1 (∵ From the symmetry, H11 = H12) ”, and it can be easily imagined that even the simple configuration shown in FIG. 8B has a crosstalk cancellation function. However, in the crosstalk cancellation processing unit 400 shown in FIG. 8A, it is guaranteed that the crosstalk can be erased according to the mathematical expression, but in the crosstalk cancellation processing unit 410 in FIG. Does not guarantee that the crosstalk can be completely erased. However, this is not a problem in the following application example.

  Now, FIG. 9 shows a configuration of a conventional apparatus having a stereo extension function to which the crosstalk cancellation processing unit 410 shown in FIG. 8B is applied. In this conventional apparatus, the FIR filter 30, the FIR filter 32, the adder 50, and the adder 52 constitute a crosstalk canceling unit 410 shown in FIG. The left channel side (Lch) input signal L0 is filtered by the high pass filter 10 and the filtered signal L1 is input to the FIR filter 30, and the right channel side (Rch) input signal R0 is filtered by the high pass filter 12. The filtered signal R1 is input to the FIR filter 32. The adder 50 adds the signal L1 and the signal R2 after the signal R1 is filtered by the FIR filter 32, and outputs the addition result as a signal L3. Similarly, the adder 52 outputs the signal R1 and the signal R1. The signal L2 after being filtered by the L1 FIR filter 30 is added, and the addition result is output as a signal R3.

  That is, in the low sound range, the wavelength of the sound wave becomes long and the effect of canceling the crosstalk is difficult to be exhibited. Therefore, the stereo input signal is divided into two bands by the low-pass filters 20 and 22 and the high-pass filters 10 and 12, and On the other hand, simple crosstalk cancellation processing is performed. Then, the adder 54 adds the signal L5 after the signal L0 is filtered by the low-pass filter 20 and the signal L4 after the signal L3 is filtered by the low shelving filter 40, and the addition result is defined as a signal L6. On the other hand, the adder 56 adds the signal R5 after the signal R0 is filtered by the low-pass filter 22 and the signal R4 after the signal R3 is filtered by the low shelving filter 42, and outputs the addition result as a signal. Output as R6.

Thus, the signal L0 and the signal R0 are input as the input signals for the left channel and the right channel, respectively, and the signal L6 and the signal R6 are the left channel output signal (Lch output) and the right channel output signal (Rch output), respectively. It was. In other words, when the left and right speakers are close to each other, as a result of performing a simple crosstalk cancellation process, the low frequency range tends to attenuate. Therefore, a low shelving filter amplifies a signal below a predetermined frequency, The separated bass signal was added and output.

Japanese Patent Laid-Open No. 5-41900 (page 2-3, FIG. 1) JP-A-10-70798 (page 3-4, FIG. 4)

  However, the main processing in the stereo expansion function described above is the crosstalk cancellation processing. However, when the input stereo signal has a large amount of monaural components, the volume of the mid-low range is not processed. (That is, compared with the case where the crosstalk cancellation process is not performed). As a result, the sound localized at the center may be smaller than the sound localized at the left and right. In other words, there is a case where a “hollow-out” occurs where a vocal or the like localized at the center can be heard thinly.

  The present invention has been made to solve such a conventional problem, and it is an object of the present invention to provide an audio device and a program capable of adjusting and controlling the amount of crosstalk cancellation to prevent “missing” and to prevent timbre deterioration. And

In order to achieve the above object, the present invention provides a crosstalk cancellation processing unit that performs processing for canceling crosstalk on each of the input signals of the left channel and the right channel,
A control coefficient calculation unit for obtaining a control coefficient for controlling the amount of crosstalk cancellation based on each of the input signals,
The crosstalk cancellation processing unit
There are two sets for the left channel and the right channel, each of which includes an FIR filter, a multiplier that inputs the output of the FIR filter, and an adder that inputs the multiplication result of the multiplier.
The multiplier for each channel is
A multiplication result obtained by multiplying the control coefficient obtained by the control coefficient calculation unit by the output of the corresponding FIR filter;
The adder for one channel is configured to add the input signal of the other channel and the multiplication result corresponding to the one channel.

In the present invention, “one channel” is a left channel (or right channel), and “the other channel” is a right channel (or left channel). That is, “one channel” is the case of the left channel and the case of the right channel, and in each case, the “other channel” is the right channel and the left channel.

According to this configuration, the crosstalk cancellation processing unit performs crosstalk cancellation processing on each of the left channel and right channel input signals. The control coefficient calculation unit obtains a control coefficient for controlling the amount of crosstalk cancellation based on the left channel and right channel input signals. The multiplier for each set of both channels multiplies this control coefficient by the output of the FIR filter for the corresponding channel, and inputs the multiplication result to the adder for the corresponding channel. The adder adds the input signal on the one channel side and the multiplication result of the corresponding multiplier for the other channel. As a result, the crosstalk cancellation amount can be controlled by the control coefficient k.

Therefore, for example, in the case of monaural sound, the control coefficient k is reduced to reduce the amount of crosstalk cancellation. On the other hand, in the case of stereo sound, the control coefficient k is increased to increase the amount of crosstalk cancellation. While maintaining the sound expansion function, it is also possible to prevent suppression of the volume of the mid-low range relative to the monaural sound. As a result, it is possible to prevent “missing” and to prevent deterioration of the timbre. In this specification, “monaural sound” means “sound with the same signal in the left and right channels”, and “stereo sound” means “sound with low correlation between the signals in the left and right channels, that is, the sound spreading left and right”. say.

Further, a more specific form of the above-described acoustic device is a configuration in which the crosstalk cancellation processing unit performs processing for canceling crosstalk on a filtered signal obtained by filtering each of the input signals with a corresponding high-pass filter. ,
A signal obtained by filtering the one channel side signal output from the crosstalk cancellation processing unit after being processed by the low shelving filter and the signal obtained by filtering the input signal on the other channel side by the low pass filter are added. The configuration includes an adder.

  That is, in this configuration, the frequency band of the input signal is divided into two bands by the high-pass filter and the low-pass filter, and the high sound side is input to the crosstalk canceling unit, while the low sound side is input to the output signal of the low shelving filter. Since the addition is performed, the crosstalk cancellation processing is not performed for the low sound range where the crosstalk canceling effect is difficult to be exhibited, and the low sound range is used for addition at the time of device output. As a result, it is possible to further prevent “missing” and sound quality degradation.

As another form, the control coefficient calculation unit may use the filtered signal instead of each of the input signals, and obtain the control coefficient based on the filtered signal. Also with this configuration, it is possible to prevent “missing” by obtaining the control coefficient using the filtered signal in the high-pass filter.

Further, the control coefficient calculation unit includes an instantaneous cross-correlation calculation unit that performs a calculation of “CC = L × R / (L ² + R ² )” where L and R are input signals of the left channel and the right channel, An envelope detection unit that obtains the envelope of the calculated value CC and a coefficient conversion unit that obtains the control coefficient based on the obtained envelope can also be used. According to this configuration, the instantaneous cross-correlation calculation unit calculates “CC = L × R / (L ² + R ² )” by setting the left channel and right channel input signals to L and R, respectively, and the envelope detection unit Obtains the envelope of the computed value CC, and the coefficient conversion unit obtains the control coefficient based on the obtained envelope, so that it is possible to realize a control coefficient computing unit capable of reducing the amount of computation with a simple configuration.

When the cross-correlation functions of the input signals of both channels are calculated correctly, the amount of calculation is considerable. Therefore, in the present invention, it is confirmed that a sufficient effect can be obtained by introducing a cross-correlation operation of “CC = L × R / (L ² + R ² )” as a simple cross-correlation function. doing. Here, CC is referred to as “instantaneous cross-correlation”, and its envelope value CE is referred to as “instantaneous cross-correlation value”. If the coefficient conversion unit is configured to obtain the control coefficient by a linear expression for the envelope value CE obtained by the envelope detection unit, the amount of calculation can be further reduced.

  In this acoustic apparatus, the signal immediately before the input of the control coefficient calculator is thinned by 1 / n, and the signal immediately after the output of the control coefficient calculator is n times (n is an integer of 2 or more). This is preferable because the amount of calculation for calculating the control coefficient can be further reduced.

According to another aspect of the present invention, a set of an FIR filter, a multiplier that inputs an output of the FIR filter, and an adder that inputs a multiplication result by the multiplier is used for the left channel and the right channel. In the sound device having two sets,
A crosstalk cancellation function that performs crosstalk cancellation processing for each of the left channel and right channel input signals;
A control coefficient calculation function for obtaining a control coefficient for controlling the amount of crosstalk cancellation based on the input signals of the left channel and the right channel;
A multiplier function for each of the multipliers for the left channel and the right channel to multiply the control coefficient obtained by the control coefficient calculation function and the output of the corresponding FIR filter and output a multiplication result;
The adder for one channel is a program for realizing an addition function for adding the filtered signal for the other channel and the multiplication result corresponding to the one channel.

  This program is recorded on a recording medium such as a ROM, for example, and a processor such as a CPU or DSP executes the program recorded on the recording medium while using a work area such as a RAM. As a result, various functions such as an input function, an addition function, and a control coefficient calculation function are realized, so that a control coefficient for controlling the amount of crosstalk cancellation can be obtained based on the input signals of the left channel and the right channel. This program can also prevent “missing” and sound quality degradation.

  According to the present invention, it is possible to provide an acoustic device or the like that can prevent “slow-out” in which a vocal or the like localized at the center can be heard and can be prevented from being deteriorated.

It is a lineblock diagram of acoustic device 1 of a 1st embodiment. 3 is a block diagram showing a configuration of a control coefficient calculation unit 60. FIG. It is a graph which shows the relationship between CE and the control coefficient k. It is a block diagram of the audio equipment 2 of 2nd Embodiment. It is explanatory drawing of the adjustment effect of a control coefficient. It is a graph which shows time changes, such as CE and a control coefficient. It is explanatory drawing of the image of a stereo expansion. 4 is a configuration diagram of crosstalk cancellation processing units 400 and 410. FIG. It is a block diagram of a conventional apparatus. It is a block diagram which shows the basic composition of an audio equipment.

  Embodiments of the present invention will be described below with reference to the drawings.

(Basic configuration / operation)
FIG. 10 is a basic configuration diagram of an acoustic device according to an embodiment of the present invention. This acoustic device is a two-channel stereo input of a left channel (Lch) input signal L0 and a right channel (Rch) input signal R0. This acoustic apparatus has a crosstalk canceling unit 410 that performs a crosstalk canceling process on a stereo signal. The crosstalk cancellation processing unit 410 includes a set for the left channel including the FIR filter 30, a multiplication unit 70 that inputs the output of the FIR filter 30, and an adder 52 that inputs the multiplication result of the multiplication unit 70. Two sets of sets for the right channel, each of which includes an FIR filter 32, a multiplier 72 that inputs the output of the FIR filter 32, and an adder 50 that inputs a multiplication result by the multiplier 72, are provided. Yes.

  The adder 50 adds the multiplication result X1 of the multiplication unit 72 and the input signal L0 of the left channel, while the adder 52 adds the multiplication result Y1 of the multiplication unit 70 and the input signal R0 of the right channel. It is configured as follows. That is, the adder 50 (or 52) for one channel adds the input signal L0 (or R0) of the other channel and the multiplication result Y1 (or X1) corresponding to the one channel. Then, the control coefficient calculation unit 63 obtains a control coefficient k for adjusting and controlling the amount of crosstalk based on the input signals L0 and R0 of both the left and right channels, and outputs this to the multiplication units 70 and 72. It is a configuration.

The multiplication unit 70 that has received the control coefficient is configured to supply the adder 52 with a value Y1 obtained by multiplying the output result of the FIR filter 30 by the received control coefficient k. Similarly, the multiplication unit 72 is configured to supply a value X1 obtained by multiplying the received control coefficient k and the output result of the FIR filter 32 to the adder 50. That is, the multiplier 50 (52) for each channel outputs a multiplication result obtained by multiplying the control coefficient obtained by the control coefficient calculator 63 and the output of the corresponding FIR filter 32 (30). Yes.

  Next, the operation will be described. First, when a stereo signal is input, it is input to the crosstalk cancellation processing unit 410. The left channel signal L0 is filtered by the FIR filter 30 to become a filtered signal L1, which is input to the multiplier 70. Similarly, the right channel signal R 0 is filtered by the FIR filter 32 to become a filtered signal R 1, which is input to the multiplier 72. On the other hand, the control coefficient calculation unit 63 obtains the control coefficient k based on the left channel signal L0 and the right channel signal R0, and the obtained control coefficient k is supplied to both multiplication units 70 and 72. Then, the multiplier 70 multiplies the output signal L1 of the FIR filter 30 and the control coefficient k, and outputs the multiplication result Y1 to the adder 52. Similarly, the multiplier 72 multiplies the output signal R1 of the FIR filter 32 and the control coefficient k and outputs the multiplication result X1 to the adder 50. The addition result of the adder 50 becomes the device output signal (Lch) on the left channel side, and the addition result of the adder 52 becomes the device output signal (Rch) on the right channel side.

Here, as will be described later, since the control coefficient calculation unit 63 performs control to change the control coefficient, it is possible to control the adjustment control for canceling the crosstalk amount for both channel signals. As a result, it is possible to prevent “missing” and timbre deterioration. As will be described in detail later, the control coefficient calculation unit 63 obtains an “instantaneous correlation function” that is not a general correlation function for both channel signals, and is a value for the obtained “instantaneous correlation function (CC)”. The control coefficient k is obtained by detecting the “instantaneous correlation function value (CE)” and performing coefficient conversion on the detected value (CE). In this way, the amount of calculation can be reduced as much as possible by using the instantaneous correlation function value.

  Below, the structure, operation | movement, effect, etc. of the audio apparatuses 1 and 2 of 1st, 2nd embodiment are demonstrated as a more concrete application structure with respect to this basic structure.

(First embodiment)
(Constitution)
FIG. 1 is a configuration diagram showing the configuration of the acoustic device 1 according to the first embodiment of the present invention. The audio device 1 is a two-channel stereo input of a left channel (Lch) input signal L0 and a right channel (Rch) input signal R0. The acoustic device 1 includes a high-pass filter 10 that passes the high band (high sound range) of the input signal L0, a high-pass filter 12 that passes the high band (high sound range) of the input signal R0, and an output signal L1 of the high-pass filter 10 FIR filter 30 that filters the output signal R1 of the high-pass filter 12, a multiplier 70 that receives the output signal L2 of the FIR filter 30, and a multiplier that receives the output signal R2 of the FIR filter 32 72, an adder 52 that inputs the multiplication result of the multiplier 70, and an adder 50 that inputs the multiplication result of the multiplier 72.

The FIR filter 30, the FIR filter 32, the multiplier 70, the multiplier 72, the adder 52, and the adder 50 constitute a crosstalk cancellation unit 410 that cancels crosstalk. That is, the crosstalk cancellation processing unit 410 is a set (set) for the left channel including the FIR filter 30, the multiplication unit 70 that inputs the output of the FIR filter 30, and the adder 52 that inputs the multiplication result by the multiplication unit 70. ), A multiplier 72 for inputting the output of the FIR filter 32, and an adder 50 for inputting the result of multiplication by the multiplier 72, there are two sets of sets for the right channel. doing.

When only the left channel signal is input, the FIR filter 30 has a listener M (not shown in FIG. 1) facing the front in the left direction of the drawing in FIG. 1 and left and right speakers arranged in the vertical direction of the drawing. Assuming that the sound is left, the sound from the left speaker is a filter for allowing the sound to reach only the left ear. Similarly, the FIR filter 32 is a filter for allowing sound to reach only the right ear of the listener M when only the right channel signal is input. Thus, the crosstalk processing unit 410 can cancel (strictly attenuate) the crosstalk.

  Further, the control coefficient calculation unit 60 receives the input signal L0 of the left channel (Lch) and the input signal R0 of the right channel (Rch) and obtains a control coefficient k for controlling the amount of crosstalk cancellation. The control coefficient k obtained by the control coefficient calculator 60 is input to each of the multiplier 70 and the multiplier 72. The multiplier 70 multiplies the output signal L2 of the FIR filter 30 and the control coefficient k and outputs the multiplication result Y1 to the adder 52. Similarly, the multiplier 72 outputs the output of the FIR filter 32. The multiplication result X1 is output to the adder 50 by multiplying the signal R2 and the control coefficient k.

  In addition, a low shelving filter 40 that filters the signal L3 indicating the addition result of the adder 50 in a predetermined pass frequency band to obtain the signal L4 is provided. Similarly, the signal R3 indicating the addition result of the adder 52 is specified. A low shelving filter 42 is provided which is filtered in the pass frequency band to be a signal R4. Furthermore, a low-pass filter 20 that filters the low band (low sound range) of the left channel input signal L0 to the signal L5, and a low pass filter 20 that filters the low band (low sound range) of the right channel input signal R0 to the signal R5. And a filter 22.

  An adder 54 that adds the output signal L4 of the low shelving filter 40 and the output signal L5 of the low-pass filter 20 is included, and a signal L6 indicating the addition result of the adder 54 is This is an output signal on the channel (Lch) side. Similarly, an adder 56 that adds the output signal R4 of the low shelving filter 42 and the output signal R5 of the low-pass filter 22 is provided, and the signal R6 indicating the addition result of the adder 56 is The output signal is on the right channel (Rch) side.

  FIG. 2 is a block diagram showing a configuration of the control coefficient calculation unit 60. The control coefficient calculation unit 60 includes an instantaneous cross correlation calculation unit 62, an envelope detection unit 64, and a coefficient conversion unit 66. In general, it is known that a cross-correlation function of two time functions f1 (t) and f2 (t) can be obtained by calculation as in the following equation (1). N is the number N of sections obtained by dividing the time interval T for calculating the cross correlation.

  C (τ) = (1 / (N + 1)) × Σf1 (t) · f2 (t + τ) (Formula 1) (where Σ is the sum from t = 0 to N)

  In the calculation according to Equation 1, since a signal in a certain section T is used, at least a delay in that section occurs. Therefore, in the present invention, it has been confirmed that if “C (0)”, which is an instantaneous cross-correlation coefficient, is obtained in order to shorten time and reduce the amount of calculation, accuracy is sufficient. Therefore, this is called “instantaneous cross-correlation” and the value is called “instantaneous cross-correlation coefficient”.

The instantaneous cross-correlation calculation unit 62 calculates “L × R / (L ² + R ² ) (Equation 2)” where “L” is an input signal of the left channel and “R” is an input signal of the right channel. This is output as CC. That is, the calculation for obtaining CC is instantaneous cross-correlation as referred to in the present invention. Next, the envelope detector 64 detects the envelope for the CC obtained by the instantaneous cross-correlation calculator 62 and sets this as CE. CE is an instantaneous cross-correlation coefficient referred to in the present invention. The envelope detector 64 can be realized by a simple low-pass filter, for example. Specifically, the value of CE is “−0.5 to +0.5”, “+0.5” in the case of a monaural signal in which the left and right signals are the same, “0” if uncorrelated, and vice versa. A phase signal is “−0.5”.

  In addition, the coefficient conversion unit 66 performs conversion using a primary conversion formula (including constants) on CE to obtain a control coefficient “k”. That is, since the control coefficient “k” can be obtained from the CE by a linear function expression “k = −a × CE + z (Expression 3)”, it can be realized with a very simple configuration. The maximum value of the control coefficient “k” is “1.0”, and as the control coefficient “k” increases, the effect of canceling the crosstalk is exhibited. On the other hand, the effect decreases as the control coefficient “k” decreases (closer to “0”). The maximum value of the control coefficient “k” is “1.0”. If the input stereo signal has a low correlation, it is determined that the left / right spread is large, and the control coefficient is brought close to “1.0”. On the other hand, if the correlation between the input signals is high, there are many monaural components. Perform processing to lower the coefficient. However, the control coefficient “k” is provided with a lower limit to maintain a certain effect.

As an example, when the constants a and z in (Expression 3) are “2” and “1.3”, respectively, the coefficient conversion expression is (Expression 4) next.
“K = −2 × CE + 1.3 (0.15 <CE <0.35),
k = 1.0 (CE ≦ 0.15),
k = 0.6 (CE ≧ 0.35) (Formula 4) ”

  FIG. 3 is a graph showing the relationship between the instantaneous cross-correlation coefficient CE and the control coefficient k. When the value of CE is “0.15” or less, the value of the control coefficient k is a constant value “1.0”, and when the value of CE is “0.35” or more, the value of the control coefficient k Becomes a constant value “0.6”. Further, when CE is larger than “0.15” and smaller than “0.35”, a value obtained by a conversion formula “k = −2 × CE + 1.3” is obtained. The control coefficient “k” has a minimum value “0.6” and a maximum value “1.0”. As can be seen from FIG. 3, basically, the larger the CE, the smaller the value of the control coefficient “k”. In this way, the control coefficient calculator 60 can obtain the control coefficient “k” based on the input signals of the left and right channels.

  In the acoustic device 1, as an example, the cutoff frequencies of the high-pass filter 10, the high-pass filter 12, the low-pass filter 20, and the low-pass filter 22 are set to “500 (Hz)”, respectively. The cutoff frequencies of the filters 10, 12, 20, and 22 are determined according to the characteristics of the speaker, and may be set to a cutoff frequency of 300 to 500 (Hz), for example. Further, in order to reduce the amount of calculation, the signal immediately before the input of the control coefficient calculation unit 60 can be thinned by 1 / n, and the signal immediately after the output of the control coefficient calculation unit 60 can be multiplied by n (where n is 2 or more). Integer).

(Operation)
Next, the operation will be described. First, the left channel (Lch) input signal L0 is filtered by the high-pass filter 10 and input to the crosstalk canceling unit 410 (signal L1). Next, the signal L1 input to the crosstalk cancellation unit 410 is filtered by the FIR filter 30. Then, the filtered signal L2 from the FIR filter 30 is input to the multiplication unit 70. Similarly, the right channel (Rch) input signal R 0 is filtered by the high-pass filter 12 and the FIR filter 32, and the output signal R 2 of the FIR filter 32 is input to the multiplier 72.

  Further, the control coefficient calculation unit 60 inputs the input signals L0 and R0 of the left channel (Lch) and the right channel (Rch), and obtains the control coefficient k as described above. The control coefficient k is output to each of the multiplication unit 70 and the multiplication unit 72. Then, the multiplier 70 receives the signal L2 and the control coefficient k, performs multiplication, and inputs a signal Y1 indicating the multiplication result to the adder 52. Similarly, the multiplier 72 receives the signal R2 and the control coefficient k, performs multiplication, and inputs a signal X1 indicating the multiplication result to the adder 50.

  The adder 50 adds the signal L1 and the signal X1 and inputs the addition result signal L3 to the low shelving filter 40. The adder 52 adds the signal R1 and the signal Y1 and adds the addition result signal. R3 is input to the low shelving filter 42. The adder 54 adds the output signal L4 of the low shelving filter 40 and the output signal L5 of the low-pass filter 20. Thus, the addition result signal L6 becomes an output signal (Lch output) on the left channel side of the acoustic device 1. Similarly, the adder 56 adds the output signal R4 of the low shelving filter 42 and the output signal R5 of the low pass filter 22, and the addition result signal R6 is an output signal (Rch) on the right channel side of the acoustic device 1. Output). Thus, for example, the acoustic device 1 can output the musical tone signals of the guitar as the input signals L0 and R0 of both the left and right channels, and output the signals L6 and R6 as the left channel side and the right channel side, respectively. Similarly, vocal sounds and the like can be applied to the apparatus 1.

  FIG. 5 is a graph of a simulation result showing the control effect by the control coefficient k. In this example, a monaural input is assumed in which the left channel input signal and the right channel input signal are the same signal. The horizontal axis represents frequency (Hz) and the vertical axis represents output relative amplitude (dB). The frequency characteristic with respect to the control coefficient “1.0” is represented by the symbol A, and the frequency characteristic with respect to the control coefficient “0.6” is represented. This is indicated by symbol B. When a monaural sound is input, as indicated by reference numeral A, the amplitude decreases in the frequency band of about 400 (Hz) to 2 k (Hz), resulting in a “hollow”. It can be seen that the reduced amplitude can be raised by controlling the amount of crosstalk cancellation to be reduced by lowering the coefficient to “0.6” (see symbol B). Thus, it can be seen that the crosstalk amount adjustment control by the control coefficient k is effective in a device having a stereo expansion function.

6 (a) to 6 (d) are experiments showing temporal changes of the left channel input signal (left signal), the right channel input signal (right signal), the instantaneous cross-correlation coefficient CE, and the control coefficient k, respectively. It is a value, and the horizontal axis represents time (t) and the vertical axis represents quantity. When signals are input to the left channel and the right channel, the instantaneous cross-correlation coefficient CE gradually increases overall, and as a result, the control coefficient k tends to gradually decrease from “1.0”. I can see the situation.

  According to this embodiment, in the case of a monaural sound in which each of the two stereo channels is the same sound, the control coefficient k is reduced to reduce the amount of crosstalk cancellation, while the correlation between the signals of the left and right channels is reduced. In the case of a stereo sound that is low, that is, a sound that spreads to the left and right, it is possible to perform control to increase the crosstalk cancellation amount by increasing the control coefficient k. As a result, while suppressing the stereo sound expansion function, it is also possible to suppress the suppression of the volume of the mid-low range with respect to the monaural sound, thereby preventing “missing” and the deterioration of the timbre.

(Second Embodiment)
(Constitution)
FIG. 4 is a configuration diagram showing the configuration of the acoustic device 2 according to the second embodiment of the present invention. Parts having the same reference numerals as those in FIG. 1 have the same functions as those in FIG. The acoustic device 2 is characterized in that a control coefficient computing device 2 is provided instead of the control coefficient computing device 1 in the acoustic device 1. The control coefficient calculation unit 2 is characterized in that the control coefficient k is obtained based on the outputs of the high-pass filter 10 and the high-pass filter 12. The control coefficient calculator 2 receives the output signals L1 and R1 of the high-pass filter 10 and the high-pass filter 12, and obtains the control coefficient k using the input signals L1 and R2. The specific configuration of the control coefficient calculator 2 includes an instantaneous cross-correlation calculator 62, an envelope detector 64, and a coefficient converter 66, as shown in FIG.

That is, the instantaneous cross-correlation calculating unit 62 obtains a cross-correlation CC (“CC = L1 × R1 / (L1 ² + R1 ² )”) from the signal L1 and the signal R2 using (Expression 2), and then detects the envelope The unit 64 obtains the CC envelope CE, and the coefficient conversion unit 66 obtains and outputs the control coefficient k from the envelope CE using the equation (4). The control coefficient k output from the control coefficient calculator 61 is output to each of the multiplier 70 and the multiplier 72. As a result, the multiplication unit 70 can input the signal L2 and the control coefficient k, and obtain and output the multiplication result of both. Similarly, the multiplier 72 can receive the signal R2 and the control coefficient k, obtain the result of multiplication of both, and output the result. Signals Y1 and X1 indicating the multiplication results by the multiplication unit 70 and the multiplication unit 72 are output to the adders 52 and 50, respectively. Since the crosstalk cancellation is applied to the band excluding the low frequency range, in the second embodiment, the control coefficient k is generated based on the signal excluding the low frequency range. is there. On the other hand, in the first embodiment, since the input to the control coefficient calculation unit does not pass through the high-pass filter, a quick reaction is possible without being affected by the delay caused by the filter.

Therefore, the adder 50 adds the signal L1 and the signal X1, and the signal L3 indicating the addition result is input to the low shelving filter 40. Similarly, the adder 52 adds the signal R1 and the signal Y1, and the signal R3 indicating the addition result is input to the low shelving filter 42. The rest of the configuration is the same as that of the acoustic device 1 shown in FIG. Further, in order to reduce the calculation amount, the signal immediately before the input of the control coefficient calculation unit 61 can be thinned by 1 / n, and the signal immediately after the output of the control coefficient calculation unit 61 can be multiplied by n (similarly) N is an integer of 2 or more).

(Operation)
Next, the operation will be described. First, the left channel (Lch) input signal L0 is filtered by the high-pass filter 10 and input to the crosstalk canceling unit 410 (signal L1). Next, the signal L1 input to the crosstalk cancellation unit 410 is filtered by the FIR filter 30. Then, the filtered signal L2 from the FIR filter 30 is input to the multiplication unit 70. Similarly, the right channel (Rch) input signal R 0 is filtered by the high-pass filter 12 and the FIR filter 32, and the output signal R 2 of the FIR filter 32 is input to the multiplier 72.

  Further, the control coefficient calculation unit 61 receives the output signals L1 and R1 of the high-pass filter 10 and the high-pass filter 20 and obtains the control coefficient k. The obtained control coefficient k is output to each of the multiplier 70 and the multiplier 72. Then, the multiplier 70 inputs the signal L2 and the control coefficient k, performs multiplication, and inputs a signal Y1 indicating the multiplication result to the adder 52. Similarly, the multiplier 72 receives the signal R2 and the control coefficient k, performs multiplication, and inputs a signal X1 indicating the multiplication result to the adder 50. The adder 50 adds the signal L1 and the signal X1, inputs the addition result signal L3 to the low shelving filter 40, and the adder 52 adds the signal R1 and the signal Y1, and outputs the addition result signal. R3 is input to the low shelving filter 42.

  The adder 54 adds the output signal L4 of the low shelving filter 40 and the output signal L5 of the low-pass filter 20. Thus, the addition result signal L6 becomes an output signal (Lch output) on the left channel side of the acoustic device 2, and similarly, the adder 56 outputs the output signal R4 of the low shelving filter 42 and the output signal R5 of the low pass filter 22. And the addition result signal R6 becomes an output signal (Rch output) on the right channel side of the acoustic device 2. In this way, like the audio device 1, the audio device 2 uses, for example, the guitar tone signal as the input signals L0 and R0 for both the left and right channels, and the signals L6 and R6 as the signals for the left and right channels, respectively. Can be output. Similarly, vocal sounds can be applied to the apparatus 2.

  Even in the acoustic device 2 having such a configuration, similarly to the acoustic device 1, it is possible to prevent “slow-out” in which a vocal or the like localized at the center can be heard and to prevent timbre deterioration.

  The apparatus described above can be realized as a circuit by hardware or can be realized by software. In the case of software, a processor (CPU, DSP, etc.) executes a program recorded on a recording medium (ROM, etc.) while using a work area (RAM, etc.), so that the audio device 1 and the audio device 2 are It is possible to realize.

  Various modifications can be made to the embodiment of the present invention described above. For example, it is possible to slightly change the cutoff frequency and frequency characteristics of each filter.

  As described above, according to the present invention, it can be used for a musical tone signal of a guitar, for example.

DESCRIPTION OF SYMBOLS 1 Acoustic apparatus 2 Acoustic apparatus 10 High pass filter 12 High pass filter 20 Low pass filter 22 Low pass filter 30 FIR filter 32 FIR filter 40 Low shelving filter 42 Low shelving filter 50 Adder 52 Adder 54 Adder 56 Adder 60 Control coefficient calculation Unit 61 Control coefficient calculation unit 63 Control coefficient calculation unit 62 Instantaneous cross-correlation calculation unit 64 Envelope detection unit 66 Coefficient conversion unit 70 Multiplication unit 72 Multiplication unit 410 Crosstalk cancellation processing unit

Claims (8)

A crosstalk cancellation processing unit that performs processing for canceling crosstalk for each of the left channel and right channel input signals;
A control coefficient calculation unit for obtaining a control coefficient for controlling the amount of crosstalk cancellation based on each of the input signals,
The crosstalk cancellation processing unit
There are two sets for the left channel and the right channel, each of which includes an FIR filter, a multiplier that inputs the output of the FIR filter, and an adder that inputs the multiplication result of the multiplier.
The multiplier for each channel is
A multiplication result obtained by multiplying the control coefficient obtained by the control coefficient calculation unit by the output of the corresponding FIR filter;
The acoustic device in which the adder for one channel adds the input signal of the other channel and the multiplication result corresponding to the one channel. The acoustic device according to claim 1,
The crosstalk cancellation processing unit
The input signal is configured to perform processing for canceling crosstalk on a filtered signal obtained by filtering each of the input signals with a corresponding high-pass filter,
A signal obtained by filtering the one channel side signal output from the crosstalk cancellation processing unit after being processed by the low shelving filter and a signal obtained by filtering the input signal on the other channel side by the low pass filter are added. An acoustic device comprising the adder. The acoustic device according to claim 2,
The control coefficient calculator is
Instead of each of the input signals, use the filtered signal,
An acoustic device for obtaining the control coefficient based on the filtered signal. The acoustic device according to any one of claims 1, 2, and 3,
The control coefficient calculator is
An instantaneous cross-correlation calculating unit for calculating “CC = L × R / (L ² + R ² )”, where L and R are input signals of the left channel and the right channel,
An envelope detector for obtaining an envelope of the calculated value CC;
And a coefficient conversion unit for obtaining the control coefficient based on the obtained envelope. The acoustic device according to claim 4,
The coefficient converter is
The acoustic apparatus, wherein the control coefficient is obtained by a linear expression with respect to the envelope value CE obtained by the envelope detector. The acoustic device according to any one of claims 1, 2, 3, 4 and 5,
A sound apparatus characterized in that the signal immediately before the input of the control coefficient calculation unit is thinned to 1 / n and the signal immediately after the output of the control coefficient calculation unit is multiplied by n (n is an integer of 2 or more). The acoustic device according to any one of claims 1, 2, 3, 4, 5 and 6.
The input signals of the one channel and the other channel are
An acoustic device characterized by including a musical tone signal of a guitar and a vocal sound. In an acoustic apparatus having two sets for a left channel and a right channel, each set includes an FIR filter, a multiplier that inputs an output of the FIR filter, and an adder that inputs a multiplication result of the multiplier.
A crosstalk cancellation function that performs crosstalk cancellation processing for each of the left channel and right channel input signals;
A control coefficient calculation function for obtaining a control coefficient for controlling the amount of crosstalk cancellation based on the input signals of the left channel and the right channel;
A multiplier function for each of the multipliers for the left channel and the right channel to multiply the control coefficient obtained by the control coefficient calculation function and the output of the corresponding FIR filter and output a multiplication result;
A program for realizing an addition function in which the adder for one channel adds the filtered signal for the other channel and the multiplication result corresponding to the one channel.

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