JPS6060071B2 - 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, the original signal content is
For example, if the input signal is a vocal, etc., reverberation has already been added to the input signal itself, so it is necessary to add more reverberation. This is not desirable since it gives an unnatural feeling to the hearing. Furthermore, in the case of monaural or small-separation program sources, such as AM broadcasting, it is possible to obtain a pleasant playback sound by adding reverberation components, but as mentioned earlier, the level of mixing of reverberation components is adjusted manually by the user. 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 and the level of reverberant sound added according to the contents of an input signal. It is an object. Hereinafter, the present invention will be explained in detail using the accompanying 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, both . Addition circuit 3 and subtraction circuit 4
is input to.

Therefore, the output of the addition circuit 3 becomes the (L+R) signal, and the output of the subtraction circuit 4 becomes the (L-R) signal. The two signals are applied to rectifier circuits 5 and 6 and integration circuits 7 and 8 having predetermined time constants, respectively, so that (L+R) and ! (L-R) signal is converted to a DC level according to the signal. Therefore, the signal conversion means is constituted by an addition or subtraction circuit, a rectification circuit, and an integration circuit. 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. Therefore, the subtraction circuit 9 and the smoothing circuit 10 constitute a difference signal generation means. The differential signal voltage that is the output of the smoothing circuit 10 is input to the single-powered gate circuits 16 and 30, and is also inverted by the inverting circuit 14 and input to the single-powered gate circuits 15 and 31. On the other hand, a voltage having a DC level according to the (LR) signal, that is, an integrating circuit 8
The output is input to a voltage comparison circuit 11 and compared with a predetermined reference voltage from a reference voltage generation circuit 12.

The comparison output signal of the comparison circuit 11 is directly used as a signal to control the opening and closing operations of the gates 16 and 31, and the output of the comparison circuit 11 is inverted by the inverting circuit 13 to control the opening and closing operations of the gates 15 and 30. . Gate circuit 1
The outputs of 5 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 in accordance with the DC voltage level output from the gate circuit. The output signal of the oscillation circuit 17 becomes a shift clock signal for delay circuits 18 and 19, such as BBD, which are composed of analog shift registers, and the L and R input signals are respectively processed by the delay circuits 18 and 19 according to the shift clock signal frequency. Delayed. On the other hand, the outputs of the gate circuits 30 and 31 are both connected to the voltage control input terminals of the voltage control attenuation circuits 20 and 21, and the amount of attenuation thereof is controlled according to the DC voltage level output from the gate circuits.

In this embodiment, the L and R input signals are first delayed by delay circuits 18 and 19, respectively, and then the next stage attenuation circuits 20 and 21 are connected in series to each of the delay circuits.
to attenuate it. The attenuated outputs are input to adder circuits 22 and 23, which are combining means, to be combined with the L and R input signals, respectively. Furthermore, the outputs of the attenuation circuits 20 and 21 are fed back to the inputs of the delay circuits 18 and 19, respectively, so that L and R signals to which appropriate reverberation has been added are obtained from the output terminals 24 and 25 of the adder circuits 22 and 23, respectively. It will be done. 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.

L=l+112C R=r+112C In equation (1), 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 SA and S of the addition and subtraction circuits 3 and 4 are expressed by the following equations. Therefore, SA and Ss are rectifier circuits 5 and 6.
and integrating circuits 7 and 8 both generate DC voltages SAD and S$
D and is expressed by the following formula.

In this), 1 indicates the average value after DC level conversion (the same applies below).

On the other hand, since l and r are completely separate random signals, l
It is considered that +r:1-r.

Therefore, the difference voltage between SAO and S, O, that is, the smoothing circuit 10
The output of can be expressed as: As can be seen from the above equation (4), the output of the smoothing circuit 10, that is, the gate circuit 1
A voltage level corresponding to the center localization component C is obtained at inputs 5 and 16.

In other words, when the C component in the input signal is large, the level of C also rises, so the inputs to the gate circuits 16 and 31 increase, while the inputs to the gate circuits 15 and 30 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=3C/2, so SAD, SSD and SAO-S,O is the following formula? Since it is clear that it is possible to determine whether the input signal is mono, dual, or stereo based on the SSD of equations (3) and (5) above, the reference voltage generator of the voltage comparator 11 Assuming the reference voltage of 12 as ■R. 1-r>V
Select a value such that R>0, and when S, D>VR, the comparator circuit 1
The output of gate circuit 1 is designed to be at the ゛゜H゛ (high) level, and to be at the ゜゜L゛ (low) level when S, D < VR, and the gate circuits 15 and 16 are opened when the control input is at the ``゜H'' level. That is, if it is brought into a conductive state, the following two cases will exist regarding the control voltage of the voltage controlled oscillation circuit 17.

First, in the case of SSD R, that is, when the input signal is monaural, the output of the comparator circuit 11 becomes the "゜L" level, so the gate circuit 15 becomes conductive via the inverting circuit 13, and the signal becomes inversely proportional to the C component. The resulting voltage becomes the control voltage of the voltage controlled oscillation circuit 17.

Next, in the case of S$D>VR, that is, 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 the stereo is applied to the voltage controlled oscillation circuit 17. This becomes the control voltage.

Here, the voltage-to-frequency conversion coefficient of the voltage controlled oscillation circuit 17 is set to KO1, and the control voltage from the gate circuits 15 and 16 is set to Vc,
If the oscillation frequency is FO and the shift register stages of the delay circuits 18 and 19 are N, the delay time Td of the delay circuit is expressed by the following equation.

That is, it can be seen that the delay time τd is inversely proportional to the control voltage ■C.

Considering the case where the input signal is a monaural source from the above relationship, when the C component increases, that is, the L and R signals are the same and the same signal level increases, Vc decreases, and therefore the delay circuits 18 and 19 The delay time τd will increase.

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, as the C component in the stereo signal increases, the control voltage Vc also increases, and therefore the delay time τd of the delay circuits 18 and 19 decreases.

That is, when the C component level is high, the signal delay time is shortened. That is, if a large amount of reverberation has already been added to the program source, the C component level is high, so the delay time by this circuit is shortened, which is advantageous. Next, in order to make the gate circuits 30 and 31 conductive in the case of the control signal ゜゜H゛ as in the case described above, the control voltage of the voltage control attenuation circuits 20 and 21 is also determined by the following two steps.
There are two cases.

In the case of SSD〈■R, that is, when the input signal is monaural, the output voltage of the comparator circuit 11 becomes ゛L゛, so the gate circuit 30 becomes conductive via the inverting circuit 13, and a voltage proportional to the C component is generated. This becomes the control voltage for the voltage control attenuation circuits 20 and 21.

Next, in the case of SSD>VR, that is, stereo, the output of the comparison circuit 11 becomes ``H'' level, the gate circuit 31 becomes conductive, and a DC voltage inversely proportional to the C component in the stereo is applied to the voltage control attenuation circuits 20 and 21. This becomes the control voltage.

In this case, the gain of the voltage control attenuation circuits 20 and 21 is equal to the control voltage V.
If the maximum gain is 1 and the input and output voltages of the attenuation circuit are υi and VO, respectively, the following equation holds true.

In this), K is a voltage-gain conversion coefficient.

Therefore, from the above equation (6), it can be seen that the output voltage (2)0 of the attenuation circuit is proportional to the control voltage Vc.

Considering the case where the input signal is a monaural source from the above relationship, the C component increases, that is, the L and R signals are the same and the same signal level increases, so that ■C increases and the output of the attenuation circuits 20 and 21 Voltage VO will also increase.

That is, in the case of a monaural source, the higher the input, the higher the level of the delayed output signal of the delay circuits 18 and 19 becomes. On the other hand, when the input signal is a stereo source, when the C component in the stereo signal increases, the control voltage ①C decreases, and therefore the output voltage VO of the attenuation circuits 20 and 21 also decreases.

That is, when the C component level is high, the delay output signals of the delay circuits 18 and 19 operate to have low levels. As detailed above, according to the present invention, a reverberation signal with a high reverberation component level and a long delay time in proportion to the input level is added to a program source with little spread, such as a monaural source. A natural reverberation effect can be obtained.

On the other hand, in the case of a stereo source, the level of the delayed signal is increased or decreased depending on the magnitude of the C component corresponding to the reverberation included in advance, and the delay time is controlled to be short or long to automatically and effectively create a natural sound. Reverberation sound is added. In this way, the device of the present invention makes it possible to add reverberation that matches the state of the program source, and especially in the case of a monaural source, the level and delay time of the reverberant sound are automatically controlled according to the input level, which improves the auditory sense. This makes it more desirable. Further, in the case of additional input such as microphone mixing, the effect of adding reverberation can be changed depending on the volume, which is advantageous. Furthermore, it can be used not only for reverberation effects but also for other acoustic effects such as phase modulation. In the above embodiment, the attenuation circuits 20 and 21 are connected to the next stage of the delay circuits 18 and 19, but conversely, the attenuation circuits 20 and 21 first control the level, and then the delay circuits are connected to the next stage. Of course, the same effect can be obtained by connecting 18 and 19 to control the delay time.

In addition, a delay circuit is provided for each of the L and R channels.
Although an attenuation circuit is used, it is also possible to combine (for example, add or subtract) the L and R channels and use a series connection circuit of one delay circuit and an attenuation circuit for the combined signal.

Further, the delay circuits 18 and 19 may have different delay times, and the attenuation circuits 20 and 21 may have different frequency characteristics. Furthermore, the same reverberation effect can be obtained by directly introducing the outputs of the attenuation circuits 20 and 21 into speakers provided separately from the original L and R channel speakers instead of the adder circuits 22 and 23. Of course.

l Brief description of the drawing The figure is a block diagram showing an embodiment of the present invention.

Claims (1)

[Claims] 1. A first signal converting means 3, 5, which generates a DC signal having a level corresponding to the sum of the first and second channel signals.
7, and second signal converting means 4 for generating a DC signal having a level corresponding to the difference between the first and second channel signals.
, 6, 8, and difference signal generating means 9, which generates a signal according to the difference between the DC signals from the first and second signal converting means.
10, comparing means 11 for comparing the DC signal from the second signal converting means and a predetermined reference voltage, and a first gate controlled by the output of the comparing means and receiving the output of the difference signal generating means as input. 16, a second gate 15 which is controlled by the inverted output of the comparing means and receives the inverted output of the difference signal generating means; and a second gate 15 which is controlled by the inverted output of the comparing means and receives the output of the difference signal generating means. a third gate 30 that is controlled by the output of the comparison means and receives the inverted output of the difference signal generation means as an input;
, a voltage controlled oscillation circuit 17 whose oscillation frequency is controlled by the first and second gate outputs, and a delay means 1 whose delay time is controlled by the output signal of the voltage controlled oscillation circuit.
8, 19, voltage-controlled attenuation means 20, 21 whose attenuation amount is controlled by the third and fourth gate outputs and which are connected in series with the delay means, and a series-connected circuit of the delay means and the voltage-controlled attenuation means. A reverberation adding device characterized in that it includes synthesis means 22 and 23 for synthesizing an output signal obtained by applying the first and second channel signals and the first and second channel signals. 2. The reverberation adding device according to claim 1, wherein the series connection circuit is configured such that the output of the delay means is connected to the input of the voltage controlled attenuation means. 3. The delay means includes first and second delay circuits that delay the first and second channel signals, respectively, and the voltage control attenuation means attenuates the output voltages of the first and second delay circuits, respectively. the combining means includes first and second voltage-controlled attenuation circuits that add the outputs of the first and second voltage-controlled attenuation circuits and the first and second channel signals, respectively; 3. The reverberation adding device according to claim 2, characterized in that it has two adder circuits. 4. The reverberation adding device according to claim 1, 2, or 3, wherein the delay means comprises an analog shift register that uses the output signal of the voltage controlled oscillation circuit as a shift signal.