JPS601800B2 - 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 audio playback equipment such as stereo sets, when playing certain program sources, a predetermined reverberation is added to obtain a playback cost that is desirable from a human perspective. A common method is to mix the signal with the original signal at a desired level using a variable 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 already has reverberation. Since the sound is added, reverberation is added, which gives an unnatural feeling to the auditory sense, which is not preferable. 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 better playback conditions in terms of intelligence, and there is a drawback that the user has to make the necessary adjustments.

The present invention has been made in view of the above-mentioned drawbacks, and therefore, it is an object of the present invention to provide a reverberation adding device that can automatically control the level of reverberant sound added depending on the content of an input signal. 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.
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 voltage that is the output of the smoothing circuit 10 is input to a one-input gate circuit 16, and is also inverted by an inverting circuit 14 and input to a 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 input to the voltage comparator circuit 11. - compared with a predetermined reference voltage.

Furthermore, the output of the comparison circuit 11 is inverted by the inverting circuit 13 to control the opening/closing operation of the gate 16. The outputs of the gate circuits 15 and 16 are both connected to a voltage control input terminal of a voltage control attenuation circuit 17, and the amount of attenuation thereof is controlled in accordance with the DC voltage level output from the gate circuit. Voltage control attenuation circuit 1
The inputs 7 and 18 are L and R signals delayed by a predetermined amount from the delay circuits 19 and 20', respectively, and are input to the attenuation circuit 1.
The respective outputs of 7 and 18 are applied to adder circuits 21 and 22 at the next stage, respectively, and are added to the L and R signals, which are the original signals input to input terminals 1 and 2, respectively, and output to output terminals 23 and 24. be done. In addition, the attenuation circuits 17 and 18
The respective outputs are fed back to the respective inputs of delay circuits 19 and 20 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 SS 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.S. This is shown by the following equation. In this), -1 indicates the average value after DC level conversion.

(The same applies hereinafter) On the other hand, since 1 and r are completely separate random signals, it is considered that b+r≠1−r.

Therefore, SAD and SS. , that is, the smoothing circuit 10
The output of can be expressed as: SAD-SS.

〒C ・・・・・・・・・{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 the gate circuit 16
The input to the gate circuit 15 will increase, while the input to the gate circuit 15 will decrease. In this case, if the program source applied to input terminals 1 and 2 is a monaural signal, L=R=*
'2, so S^ can be expressed as in the case of the stereo signal described above.

, SSD and SAD-SSD are expressed as follows. Above '3}
and SS of formula {5}.

It is clear that it is possible to judge whether the input signal is monaural or stereo based on the DC level, so now, assuming that the reference voltage of the reference voltage generator 12 of the voltage comparator 11 is VR, 11r>VR> Select a value of 0 and set it to SS. > The output of the comparator circuit 11 is designed to be at "H" (high) level when it is VR, and to be at "L" (low) level when it is VR like S, and the gate circuits 15 and 16 are If the voltage-controlled attenuation circuits 17 and 18 are opened or conductive, the following two cases will exist regarding the control voltages of the voltage-controlled attenuation circuits 17 and 18. First, when SSD<VR, that is, when the input signal is a monoram, the output of the comparison circuit 11 is “L”.
Therefore, the gate circuit 16 becomes conductive via the inversion circuit 13, and a voltage proportional to the C component becomes the control voltage of the voltage control attenuation circuits 17 and 18. Next, SS.>VR, that is, in the case of stereo The output of the comparison circuit 11 is “H”
' level, the gate circuit 15 becomes conductive, and a DC voltage inversely proportional to the C component in the stereo is applied to the voltage control attenuation circuit 17.
, 18 control voltages. ) voltage control attenuation circuit 17
, 18 are proportional to the control voltage VC, and if the maximum gain is 1, the attenuation circuit input and output voltages are respectively vi
and vo, the following equation holds true.

V.

= Mamoru Vi (VC/k≦1).・・・．・■(6) Here, k' is the voltage-gain conversion coefficient. Therefore, it can be seen from the above equation that the output voltage vo 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, if the C component rises, the L and R signals are the same, and the same signal level rises, so VC increases, and therefore the attenuation circuits 17 and 18 The output voltage vo will also increase.

In other words, in the case of a monaural source, the higher the input, the higher the level of the delayed signal. On the other hand, considering the case where the input signal is a stereo source, when the C component in the stereo signal increases, the control voltage VC decreases, and therefore the attenuation circuit 17,1
8's output voltage vo also decreases.

That is, when the C component level is high, the delay signal is operated to have a low level. That is, if a large amount of reverberation has already been added to the program source, the level of the C component will be high, so this circuit advantageously reduces the reverberation component level. As detailed above, according to the present invention, for a program source with little spread, such as a monaural source, a large reverberation component can be obtained in proportion to the input level, and a natural reverberation effect can therefore be obtained. It will be done.

On the other hand, in the case of a stereo source, the level of the delayed signal is controlled to be small or large according to the magnitude of the C component corresponding to the reverberation included in advance, thereby automatically and effectively adding natural reverberation. In this way, the device of the present invention makes it possible to add reverberation that matches the state of the program source.
Particularly in the case of a monaural source, the reverberation is automatically controlled according to the input level, making it more pleasing to the ear. Furthermore, in the case of additional inputs such as microphone mixing, it is convenient to be able to change the effect of adding reverberation depending on the volume.Furthermore, it can be used not only for reverberation effects, but also for adding other acoustic effects such as phase modulation. It is also possible to develop it into applications. In the above embodiments, L and R
A delay circuit and an attenuation circuit were used for each channel, but L, R
One delay circuit and one attenuation circuit may be provided for synthesizing (for example, adding or subtracting) channel signals and delaying and attenuating the synthesized signal.

Furthermore, the delay circuits 19 and 201 may have different delay times, the attenuation circuits 17 and 18 may have frequency characteristics, or they may have different frequency characteristics. Furthermore, the addition circuit 21,
22, the reverberation effect can also be obtained by directly introducing the outputs of the attenuation circuits 17 and 18 into speakers other than the original L and R channel speakers.

[Brief explanation of drawings]

The figure shows 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 that is controlled by the output of the comparing means and receives the inverted output of the difference signal generating means; and a second gate circuit that is controlled by the inverted output of the comparing means and receives the output of the difference signal generating means. a circuit, a delay means for delaying the first and second channel signals, and a delay means for delaying the first and second channel signals;
and voltage control attenuation means for attenuating the output signal of the delay means while the amount of attenuation is controlled by the output of a second gate circuit, and synthesis for combining the output of the voltage control attenuation means and the first and second channel signals. A reverberation adding device characterized by comprising: means. 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 delay means has first and second delay circuits that respectively delay the first and second channel signals, and the voltage controlled attenuation means has a first and second delay circuit that attenuates each output of the first and second channel signals, respectively. 3. The reverberation adding device according to claim 1, further comprising a first voltage control attenuation circuit and a second voltage control attenuation circuit. 4. The reverberation adding device according to claim 1, wherein the synthesizing means includes an addition circuit that outputs the sum of the output of the voltage-controlled attenuation means and the first and second channel signals.