JPS6237880B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal processing circuit, and particularly to a signal processing circuit suitable for use in a stereo signal processing circuit.

Among stereo playback devices, particularly small tape recorders and FM stereo receivers, there is a drawback in that the speaker spacing is small, resulting in a lack of sound spaciousness and the inability to obtain a sufficient stereo effect. Various measures have been proposed to solve this problem, but they are not sufficient. For example, there is a method in which a general listening position is set and the transfer function is corrected at that position to create a sense of spaciousness in the sound field, as if the speakers were installed at wide intervals. The effect changes greatly depending on the condition, which is not preferable.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a signal processing circuit that generates a signal for improving the sense of sound spread from a speaker system in a small stereo reproduction device and enhancing the sense of stereo realism.

The present invention utilizes the fact that the perceptual spread of sound corresponds to the inter-signal correlation coefficient, and its feature is that when an audio signal or the like is stationary, the input signal is irregular (hereinafter referred to as stationary). (referred to as an irregular signal) and a delayed signal of this input signal to generate uncorrelated first and second signals whose correlation coefficients are zero, and convert the first and second signals into the first and a second variable attenuator, the outputs of both attenuators are added together, the inverted output of the first attenuator and the output of the second attenuator are added, and the first and second variable attenuators are attenuated. The purpose of this invention is to control the ratio of both attenuation amounts of the device so that the correlation coefficient between these summed signal outputs can be selected as desired.

The present invention will be explained below using the drawings.

FIG. 1 is a circuit block diagram of an embodiment of the present invention, in which two signals OUT-1 and OUT-2 having a predetermined correlation coefficient with each other are obtained from a steady irregular signal IN. That is, the steady irregular signal e(t) becomes one input of the adder circuit 2 via the delay element 1, which is, for example, a comb filter, and is also inverted by the phase inverter circuit 3 and becomes one input of the adder circuit 4. ing. The steady irregular signal is also input to the direct adder circuits 2 and 4. The respective outputs A(t) and B(t) of these adder circuits are applied to variable attenuators 5 and 6 whose attenuation amounts α and β are respectively controlled by respective control signals CONT, and are attenuated. The output of the attenuator 5 directly serves as one input of the adder circuit 7, and also becomes one input of the adder circuit 9 after being phase-inverted by the inverter circuit 8. The output of the attenuator 6 is also input to the adder circuits 7 and 9, and the outputs of the adder circuits 7 and 9 are OUT-1 and OUT-1, respectively.
OUT-2 is used as two signals having a desired correlation coefficient with each other.

Here, the signal delay time in delay circuit 1 is τ
Then, the outputs A(t) and B(t) of the adder circuits 4 and 2 are as shown in the following equations.

Then, there are generally two stationary non-random signals x
The correlation coefficient R between (t) and y(t) is expressed by the following equation.

Here, () ² and () ² are each x(t)
² , y(t) indicates the time average of ² , and ()・
(t) indicates the time average of x(t)·y(t). Therefore, the correlation coefficient of the two signals shown in equation (1) is as follows.

If we transform the numerator of formula (3), we get Since e(t) and e(t-τ) are stationary random signals, the above molecule becomes zero, and A(t),
It can be seen that the two signals B(t) are mutually uncorrelated signals with a correlation coefficient of zero.

Further, the outputs e ₀₁ (t) and e ₀₂ (t) of the adder circuits 7 and 9 are expressed by the following equations.

Therefore, the correlation coefficient between both outputs is expressed as follows using equation (2).

Here, Applying the relational expression to equation (5) and rearranging it, the following equation is obtained.

R=1−H ² /1+H ² ...(7) When H (=β/α) in equation (7) is changed from zero to +∞, the output between e ₀₁ (t) and e ₀₂ (t) The correlation coefficient R changes continuously from -1 to +1. Therefore, by controlling the attenuation amounts α and β using the control signals CONT of the attenuators 5 and 6 and appropriately selecting the ratio H=β/α, one stationary irregular signal e(t) can be obtained. It becomes possible to generate two signals e _01(t) and e ₀₂ (t) having arbitrary correlation coefficients from .

FIG. 2 shows a circuit block in which stereo reproduction signal processing is performed using the signal processing circuit 10 of FIG. 1 to obtain a sense of expansion of the sound field. In the figure, parts equivalent to those in FIG. 1 are designated by the same reference numerals. Reproduction 2-channel stereo signal L(t), R
(t) is BEF (band elimination filter) 1
1 and 12 respectively of adder circuits 13 and 14
It becomes input. Also, both channel signals L(t), R
(t) is L(t)+R(t) in the adder circuit 15.
and is applied to a BPF (band pass filter) 16. The output of this BPF 16 becomes the stationary irregular signal e(t) of the signal processing circuit 10 according to the present invention, and two signals e _01(t) and e ₀₂ (t) whose mutual correlation coefficients can be set arbitrarily are obtained. becomes. These two signals serve as inputs to the adder circuits 13 and 14, respectively, and the addition outputs of the adder circuits 13 and 14 are the left and right channel reproduction signals subjected to signal processing, respectively.
L'(t) and R'(t) drive the speaker system.

By doing this, it is possible to create a sense of sound expansion even in a stereo system with narrow spacing. Basically, the attenuator 5,
The attenuation ratio H of 6 is controlled.

In addition, the steady irregular signal is BEF11, 12 and
It is divided into three by BPF16, but in order to prevent the low range from being affected by the timbre change due to the effect of the comb filter as delay element 1, and to prevent the high range from contributing particularly greatly to the sense of spaciousness, the BEF
11 and 12 allow it to pass through as is. Then, the signal processing circuit 10 performs signal processing on the intermediate band that contributes most to the sense of spaciousness of the sound using the BPF 16, thereby making the stereo sense of presence even more effective.

As described above, according to the present invention, an uncorrelated signal generation circuit that obtains signals that are uncorrelated with each other can be easily constructed, and the entire signal processing circuit can also be constructed with a simple circuit configuration, so that it can be used for stereo radio cassettes with narrow speaker spacing, etc. TV
A signal processing circuit that can expand the reproduction sound field of a stereo reproduction system such as an audio multiplex receiver can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of an example of a stereo reproduction system using the circuit block of FIG. 1. Explanation of symbols of main parts, 1...delay circuit, 2,
4, 7, 9... adder circuit, 5, 6... variable attenuator.

Claims (1)

[Claims] 1 An uncorrelated first signal whose correlation coefficient is zero using an irregular input signal and a delayed signal of this input signal
and uncorrelated signal generating means for generating a second signal, first and second variable attenuation means for attenuating the first and second signals, respectively, and outputs of the first and second variable attenuation means. and a second addition means that adds the inverted output of the first variable attenuation means and the output of the second variable attenuation means, The signal processing circuit is configured to control the ratio of both attenuation amounts of the variable attenuation means to select a desired correlation coefficient between each output signal of the first and second addition means, the signal processing circuit comprising: The signal generating means includes a delay means for delaying the input signal, an addition circuit for adding the delayed signal and the input signal, and an addition circuit for adding the inverted signal of the delayed signal and the input signal, A signal processing circuit characterized in that each output of these adder circuits is used as the first and second signals, respectively.