JPS601799B2 - Reverberation adding device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reverberation adding device, and more particularly to a reverberation adding device capable of adding reverberation to stereo and monaural audio signals.

In sound reproduction equipment such as stereo sets, when playing certain program sources, a predetermined reverberation is added to obtain a reproduction sound that is pleasing to the ear. A common method is to mix the signal with the original signal at a desired level using a resistor or the like.

However, with this method, a constant level of reverberation is added regardless of the original signal content, so for example, if the input signal is a vocal, etc., the input signal itself may already have reverberation. Since sound is added, reverberation is added, which gives an unnatural feeling, which is not desirable. Furthermore, in the case of monaural or program sources with small separation, such as AM broadcasting, it is possible to obtain a pleasant playback sound by adding reverberation components, but as mentioned earlier, the mixing of reverberation components requires the user to manually adjust the level. Therefore, it is necessary to create playback conditions that are better for audibility, and there is a drawback that the adjustment is troublesome on the user's side.

The present invention has been made in view of the above-mentioned drawbacks, and it is therefore an object of the present invention to provide a reverberation adding device that can automatically control the amount of delay of reverberant sound to be added depending on the content of an input signal. Hereinafter, the present invention will be explained in detail using additional drawings.

The figure is a block diagram showing an embodiment of the present invention. In the figure, left and right channel signals (hereinafter abbreviated as L and R signals) of a stereo signal, which is a program source, are input to input terminals 1 and 11, respectively.
and 2, and both are input to the addition circuit 3 and the subtraction circuit 4.

Therefore, the output of the addition circuit 3 becomes a (L+R) signal, and the output of the subtraction circuit 4 becomes a (L-R) signal. These two signals are applied to rectifier circuits 5 and 6 and integration circuits 7 and 8 having predetermined time constants, respectively, and are converted into DC levels according to the (L+R) and (LR) signals. These DC signals are both input to the DC subtraction circuit 9, and a voltage corresponding to the difference between the two is outputted via the subtraction circuit 9 and the next stage smoothing circuit 10. The difference signal that is the output of the smoothing circuit 10 is input to the one-input gate circuit 16, and is also input to the inverting circuit 1.
4 and is similarly input to the one-input gate circuit 15. On the other hand, the voltage having a DC level corresponding to the (LR) signal, that is, the output of the integrating circuit 8 is output to the voltage comparator circuit 11.
and is compared with a predetermined reference voltage.

The comparison output signal of the comparison circuit 11 is directly used as a signal to control the opening/closing operation of the gate 16.
1 is inverted by an inverting circuit 13 to control the opening/closing operation of the gate 15. The outputs of the gate circuits 15 and 16 are both connected to a voltage control input terminal of a voltage controlled oscillation circuit 17, and the oscillation frequency thereof is controlled according to the DC voltage level output from the gate circuit. The output signal of the oscillation circuit 17 is composed of an analog shift register, for example, BBD.
It becomes a shift clock signal for delay circuits 18 and 19 such as
The L and R input signals are delayed by delay circuits 18 and 19, respectively, according to their shift clock signal frequencies. The output amplification circuits 20 and 21 amplify the signals to a predetermined level and lower the impedance, respectively, and output the signals to output terminals 22 and 23. The outputs of the delay circuits 18 and 19 are fed back to their respective inputs via predetermined attenuation circuits 24 and 25, respectively, and are combined to obtain L and R signals to which appropriate reverberation has been added. The operating principle and effects of the above-mentioned circuit will be described below.

When the input signal is a stereo signal, the L and R signals can be expressed as follows.

In this), 1 and r are sound image components localized to the left and right, respectively, during stereo reproduction, and c is a sound image component localized to the left and right center as a virtual image.

Therefore, the outputs S^ and S3 of the addition and subtraction circuits 3 and 4 are expressed by the following equations. Therefore, S^ and SS are rectifier circuits 5 and 6
and DC voltage S^ by integral circuits 7 and 8.

and S skin, which is expressed by the following equation. In this), -1 indicates the average value after DC level conversion (the same applies below).

On the other hand, since 1 and r are completely separate random signals, 1
It is thought that 10 r nee r becomes.

Therefore, S^. and S.S. , that is, the smoothing circuit 10
The output of can be expressed as: S^.

-SS. nik ”””…[4' Above {4}
As can be seen from the equation, a voltage level corresponding to the center localization component c is obtained at the output of the smoothing circuit 10, that is, at the input of the gate circuits 15 and 16. In other words, if the c component in the input signal is large, the level of c also increases, so gate circuit 1
The input of gate circuit 15 will increase, while the input of gate circuit 15 will decrease. In this case, if the program source applied to input terminals 1 and 2 is a monaural signal, it can be expressed as L=R=pine/2, so S^ can be expressed in the same manner as in the case of the stereo signal described above. , SS. and S^. -SS.
is the following formula. S^D=SS.

Secondary (>0) SS.

=L-R20. ．． ．． ...(5)S^. =L
+R (>0) Since it is clear that it is possible to determine whether the input signal is monaural or stereo based on the SSD in equations '3} and {5) above, the voltage comparator 11 The reference voltage of the reference voltage generator 12 is set as VR, and a value of 1r>VR>0 is selected.

>When in VR, the output of comparison rotation 11 is “H” (high) level, SS. <The voltage controlled oscillation circuit should be designed so that it is at the "L" (low) level during VR, and the gate circuits 15 and 16 are open or in a conductive state when the control input is at the "H" level. The following two cases will exist regarding the 17 control voltages. First of all, SS.

<In the case of VR, that is, if the input signal is monaural,
The output of the comparator circuit 11 becomes "L" level, the gate circuit 15 becomes conductive via the inversion circuit 13, and a voltage inversely proportional to the c component becomes the control voltage of the voltage controlled oscillation circuit 17.
Next is SS.

>VR, that is, in the case of stereo, the output of the comparator circuit 11 becomes "H'' level, the gate circuit 16 becomes conductive, and a DC voltage proportional to the c component in stereo becomes the control voltage of the voltage controlled oscillation circuit 17. ), the voltage controlled oscillation circuit 1
The voltage-frequency conversion coefficient of 7 is Ko, gate circuit 15,1
If the VC oscillation frequency of the control voltage from 6 is fo, and the shift register stage of the delay circuits 18 and 19 is N, the delay time 7d of the delay circuit is expressed by the following equation.

＼? d=Rare=Red CI----.-. Side-separated control voltage V.

It can be seen that the delay time 7d is inversely proportional to the delay time 7d. Considering the above relationship, if the input signal is a monaural source,
When the c component increases, that is, when the L and R signals are the same and the same signal level increases, VC decreases, and therefore the delay time 7d of the delay circuits 18 and 19 increases.

In other words, in the case of a monaural source, the signal delay time increases as the input becomes larger. On the other hand, considering the case where the input signal is a stereo source, when the c component of the stereo signal increases, the control voltage VC also increases, and the delay time 7d of the delay circuits 18 and 19 decreases.

That is, when the c component level is high, the signal delay time is operated to be short. That is, when a large amount of reverberation has already been added to the program source, the level of the c component is high, so the delay time by this circuit is shortened, which is advantageous. As detailed above, according to the present invention, for a program source with little spread, such as a monaural source, a long delay time can be obtained in proportion to the input level, and therefore a natural reverberation effect can be obtained. In a stereo program source, natural reverberation can be automatically and effectively added by controlling the delay time to be short or long according to the magnitude of the c component corresponding to the pre-included reverberation.

In this way, the device of the present invention makes it possible to add reverberation that matches the state of the program source, and in particular, in the case of a monaural source, the reverberation is automatically controlled according to the input level, which is preferable from a user's perspective. . Furthermore, in the case of additional inputs such as microphone mixing, it is convenient to be able to change the degree of effect of adding reverberation depending on the amount of input. It is also possible to develop applications such as adding acoustic effects such as phase modulation. In the above embodiment, a delay circuit was used for each of the L and R channels, but it is also possible to combine the L and R channels (for example, by addition or subtraction) and provide one delay circuit for the combined signal. Good too.

Furthermore, the delay circuits 18 and 19 may have frequency characteristics, or may have different frequency characteristics. The outputs of the delay circuits 18 and 19 are fed back to the input via the attenuation circuits 24 and 25, and the L and R channel signals and the delayed signals are synthesized, respectively, and output signals including reverberation are obtained at the terminals 22 and 23. It is also possible to obtain a reverberation effect by directly introducing the signals of the output terminals 22 and 23 to the original L and R channel speakers, respectively, to the 8U speakers.

Furthermore, the same effect can be obtained by providing adder circuits after the terminals 22 and 23, respectively, and adding and combining the L and R channel signals and the output signals of the output terminals 22 and 23.

[Brief explanation of drawings]

The figure is a block diagram showing an embodiment of the present invention.

Claims (1)

[Scope of Claims] 1. A first signal conversion means for generating a DC signal having a level corresponding to the sum of first and second channel signals, and a first signal converting means for generating a DC signal having a level corresponding to the difference between the first and second channel signals. a second signal converting means for generating a DC signal having a
and a difference signal generating means for generating a signal corresponding to the difference between the DC signals from the second signal converting means, and a comparing means for comparing the DC signal from the second signal converting means and a predetermined reference voltage; a first gate circuit controlled by the output of the comparing means and receiving the output of the difference signal generating means; and a second gate circuit controlled by the inverted output of the comparing means and receiving the inverted output of the difference signal generating means. a voltage-controlled oscillation circuit whose oscillation frequency is controlled by the outputs of the first and second gate circuits; and a voltage-controlled oscillation circuit whose oscillation frequency is controlled by the output signals of the voltage-controlled oscillation circuit; and the first and second channel signals whose delay times are controlled by the output signals of the voltage-controlled oscillation circuit. 1. A reverberation adding apparatus comprising: a delay means for delaying the delay means; and a synthesis means for synthesizing the output of the delay means and the first and second channel signals. 2. The first signal conversion means includes an adder circuit that outputs the sum of the first and second channel signals, a first rectifier circuit that rectifies the output of the adder circuit, and integrates the output of the first rectifier circuit. a first integrating circuit, and the second signal converting means includes a subtracting circuit that outputs the difference between the first and second channel signals, a second rectifying circuit that rectifies the output of the subtracting circuit, and the second signal converting means 2. The reverberation adding device according to claim 1, further comprising a second integrating circuit that integrates the output of the rectifying circuit. 3. The reverberation adding device according to claim 1 or 2, wherein the delay means is an analog shift register that uses the output signal of the voltage controlled oscillation circuit as a shift signal. 4. Reverberation addition according to claim 1, 2, or 3, wherein the delay means includes first and second delay circuits that respectively delay the first and second channel signals. Device.