JPH02177800A - Automatic controller for sound field effect - Google Patents

Abstract

PURPOSE:To apply a natural sound field effect by providing a differential signal generation circuit to output the difference of two signals which form stereophonic broadcast, and applying the sound field effect on the output of the differential signal generation circuit when an audio signal is set at a voice part. CONSTITUTION:When the part is judged as the voice part, a control signal 17 changes to a low level, and a SW3 and a PT4 are energized and a SW1 and a SW2 are de-energized. Therefore, output from the differential signal generation circuit 21 is inputted to a sound field effect circuit 23. The differential signal generation circuit 21 offsets a signal with in-phase, and derives a signal with different phase as the differential signal output of input signals (1) and (2). The input signals 1 and 2 in the stereophonic broadcast are broadcasted with in-phase so that the voice signal of a chairman, etc., can normally be positioned in the center of two, right and left, speakers, and the cheering of an audience are broadcasted with different phase. Therefore, no voice signal of the chairman, etc., appears on output terminals (c) and (d) since it is offset by the differential signal generation circuit 21. Also, the cheering of the audience appears on the output terminals (c) and (d), and a processing by the sound field effect circuit 23 is applied on it.

Description

[Detailed Description of the Invention] [Objective of the Invention J (Field of Industrial Application) This invention provides a sound field effect adding device for adding sound field effects such as presence (surround effect) and reverberation to an audio signal. The present invention relates to an automatic sound field effect control device that prevents a sound field effect applied to a part from appearing on an audio part.

(Prior Art) Today, technological progress in the field of audio has been remarkable, and technology has been transitioning from monaural to stereo, and even from analog to digital, in order to get closer to the original sound. Furthermore, in recent years, there has been a high demand for technology that processes music sources and the like to form original sound fields according to listeners' preferences.

To meet these demands, there are two types of sound effect devices, for example, called surround systems.

The surround system is as shown in Figure 7.

A sound field effect circuit is added to the audio system.

In FIG. 7, reference numeral 1 denotes an audio input terminal for inputting audio signals from a CD, tape recorder, etc. The audio signal input to audio input terminal 1 is as follows.

The signal passes through a low-pass filter 2 and is converted into a digital signal by an A/D converter 3.

The sound field effect circuit 4 is composed of a d-folder, an adder 2 multiplier, etc., and uses digital processing to generate reverberant sound signals that can be heard from the front and rear of the concert hall or room. These digital original signals and reverberant sound signals are each converted into an analog signal by a D/A converter 5.6, passed through a low-pass filter 7.8° and amplifiers 9 and 10, and then sent to the front left and right speakers 11 and the rear speakers. The sound is amplified by the left and right speakers 12 on the side.

By adding the above sound field effect circuit to the audio system,!
! A sound field is formed to surround the listener, allowing the listener to experience a sense of presence as if they were in a concert hall or sports venue.

By the way, in the above-mentioned sound effect device, for example, when creating an atmosphere equivalent to a concert hall,
It generates reverberant sound for about 1 to 2 seconds, but the reverberant sound is added not only to music scenes, but also to scenes where the presenter appears, making it unnatural and difficult for the listener to hear. There is a problem.

In addition, the platform provides a sense of presence equivalent to that of a sports venue.

The sound field effect circuit 4 generates an echo sound at, for example, several 100 m5ec. Echo sounds are heard not only when the ISJ audience is cheering, but also on the host and commentators.

In order to solve the above-mentioned problems, conventionally, a syllable detection circuit 13 generates a binary signal without indicating which part it is, based on the characteristics of the voice part and musical tone part in the audio signal. For example, we would like to propose a circuit in which a logic circuit 14 determines whether an audio signal is a music part or a voice part of a single person's voice based on the signal. The output of the logic circuit 14 becomes a control signal that controls the sound field effect circuit 4, so that in the case of a musical tone part, a signal with a sound field effect added is output, and in the case of a voice part, a signal with a sound field effect added is output. (See Figure 7).

However, it is difficult to determine whether an audio signal is a musical tone part or a voice part, and accurate control is impossible. For example, in a sports game, the host's voice may be louder than the audience's cheers.

The syllable detection circuit 13 makes an incorrect determination, and the sound field effect circuit 4 outputs the original signal. As a result, the host's voice and the audience's cheers are treated equally, and no sound field effect is applied. The opposite case also occurs. In such a case,
The sound field effect is added to the audio signal, reducing the intelligibility.

(Problems to be Solved by the Invention) In conventional sound field effect devices, it is not easy to accurately determine whether an audio signal is a voice part or a musical tone part and to switch the sound field effect. For this reason, 1. For example, when watching sports, the sound field effect may be applied to the host's voice, making it unclear, or the sound field effect may or may not be applied to the audience's cheers, creating an unnatural sound field. The drawback was that it resulted in effect control.

The object of the present invention is to provide an automatic M field effect control device that eliminates the above problems and provides a natural sound field effect.

[Structure of the Invention] (Means for Solving the Problems) This invention provides a difference signal creation circuit that outputs the difference between two signals for stereo transmission among audio signals consisting of a plurality of channels, and the audio signal is a voice part. At the time,
The present invention is characterized in that a sound field effect is applied to the output of the difference signal generating circuit.

(Function) The audio signal during stereo transmission is produced so that the audio signal of the presenter, etc. is localized at the center of the two left and right speakers by reproduction. Such a signal is transmitted as a two-channel in-phase signal. According to this invention,
By extracting the difference component of the audio signal, only signals with different phases between the two channels can be output from the difference signal generation circuit, and signals with the same phase can be canceled out. Therefore.

In the case of an audio source where the host's voice and the audience's cheers are mixed, such as in a sports scene.

Even if the content of the audio signal is incorrectly determined, the sound field effect is not automatically applied to the host's voice, but is applied to the audience's cheers.

(Example) FIG. 1 is a block diagram showing one embodiment of the present invention.

In FIG. 1, input signals (1) and (2) are two-channel audio signals transmitted by stereo transmission.

Input as a digital signal after A/D conversion. These input signals (2) and (2) become output signals (2) and (2) to the front side bias, but are also input to the syllable detection circuit 24 and the difference signal generation circuit 21.

The difference signal generation circuit 21 is a circuit that inputs the input signals ■ and ■ to a subtracter through input terminals a and b, respectively, and divides the difference signal into two signals and derives them from output terminals c and d.

The two output signals from the difference signal generation circuit 21 are supplied to a switching circuit 22 that selects the signal to be introduced into the sound field effect circuit 23.

That is, the switching circuit 22 is composed of four switches SW1 to SW4. Among these switches SW1 to SW4,
Switches SW1 and SW2 are respectively used in difference signal generation circuit 2.
1 is bypassed, between the input terminal a of the difference signal creation circuit 21 and one input terminal 0 of the sound field effect circuit 23, and between the input terminal of the difference signal creation circuit 21 and the other input of the sound field effect circuit 23. Connect between terminals 1. In addition, switches SW3 and S
W4 is the output terminal C of the difference signal creation circuit 21, the input terminal e of the sound field effect circuit 23, and the difference signal creation circuit 2, respectively.
1 and the input terminal 1 of the sound field effect circuit 23.

The sound field effect circuit 23 is a digital audio processor that adds surround effects, for example, and outputs sound field effect output signals 2, 2,
■Generate.

The syllable detection circuit 24 will be described later.

Utilizing the fact that the voice part and the rakuro part each have characteristic parts, a binary signal indicating the part is output.

This binary ° signal is input to the logic circuit 25. As a result, the logic circuit 25 generates a control signal that determines the switching from the audio part to the musical tone part and the switching from the musical tone part to the audio part. Each of the switches SW1 to SW4 of the switching circuit 22 is controlled to be conductive or non-conductive by a control signal from the logic circuit 25.

Next, a specific example of the syllable detection circuit 24 will be explained with reference to FIG.

This circuit shows a circuit that determines one of the input signals ■ and ■.TF'3G indicates the input signal ■ or ■.

It is supplied to one input terminal of the analog comparator 5.

At the other input terminal of the analog comparator 5, a threshold voltage for detecting the fluctuation part of the envelope is set by a trimmer component such as a variable resistor, in order to distinguish between the musical tone part and the voice part in the input audio signal. is applied. Thereby, a signal is obtained from the analog comparator 15 that distinguishes between a flat part where the amplitude of the input audio signal is larger than the threshold voltage and a fluctuating part where the amplitude is small.

The output of the analog converter 15 is input to a retrigger type monostable multivibrator 16. This monostable multi-byte 16 has outputs Q,
G is taken out, and one output Q is supplied to one input terminal of the Nandts gate 18 via a waveform shaping circuit 16a constituted by a diode, a capacitor, etc., and the output port is supplied to one input terminal of the Nandts gate 11. Said Nantes Gate 18
The output of is fed to a retrigger monostable multivibrator 19 which feeds the output page back to the other input of the Nant gate 18. The monostable multivibrator 19 with this configuration allows
A binary signal in which all the fluctuation parts are detected can be obtained. This binary signal also enters the other input terminal of the sund gate 17 and is logically compared with the output from the monostable multivibrator 16. The monostable multivibrator 19 has a longer metastable period than the monostable multivibrator 16.

As a result, the output of the Nandt gate 17 represents a binary signal in which only the fluctuation part longer than a certain time is picked up as an index. The reason for picking up the variable portions of the binary signal that are longer than a certain time width is based on the characteristics of the audio signal.

Next, the configuration of the logic circuit 25 will be explained.

In FIG. 3, terminal TP5 derives a binary signal from terminal TP4 in FIG. And terminal T
The binary signal from P5 is sent to the flip-flop circuit 31a.
, 31b and an AND gate 31c. In this fall detection circuit 31, each flip 70 knob 31a, 31b is operated by a clock signal from a clock generator 30. A detection pulse indicating the fall of the binary signal is derived from the AND gate 31c and input to the (first) counter 33.

The counter 33 sends the count output to comparators 35 and 36 via a flip-flop 34 with a latch function.
supply to. These comparators 35, 36.

The register values from the registers 37 and 38, each of which has been set in advance, are compared with the count value from the flip-flop array 34. The comparison result of the comparator 35 is input to one end of the latch circuit 41 and the AND gate 44 via the NOT circuit 45, and the comparison result of the comparator 36 is input to the counter 39 via the AND gate 43.

The counter 39 uses the register value set in the register 40 as an overflow value, and outputs the ant gate 4.
The output of the comparator 36, which is inputted through the comparator 36, is counted. Therefore, when the register value set in the output register 40 of the comparator 36 is exceeded, the counter 39 outputs the output as a carry signal to the not circuit 46.
are supplied to the other ends of the latch circuit 41 and the AND gate 44, respectively.

On the other hand, a counter 32a and a flip-flop 32b.

The circuit constituted by 32c is a timing signal generation circuit that operates in response to a clock signal from the clock generator 30. This timing signal generation circuit 32 sends a signal to the flip-flop 32 to clear the counter 33.
From b, a signal - which causes the flip-flop 34 to perform a latch operation is outputted from the flip-flop 32C, respectively.
It supplies the specified circuit.

The audio signal is divided into predetermined unit sections by the outputs of these flip-flops 32b and 32c. Incidentally, the output of the flip-flop 32c is also supplied to the other input terminal of the AND gate 43. The clock generator 30 also drives counters 33 and 39.

Thus, the latch circuits 41 are connected to the comparators 35 and 35, respectively. The output based on the counter 39 is led out to the terminal TP6 via the 7-lip flop block 42. This terminal TP6
The signal derived from this becomes a control signal for controlling the switching circuit 44 in FIG.

Next, the operation of the configuration shown in FIG. 1 will be explained.

First, FIGS. 4 and 5 show timing charts illustrating the operations of the syllable detection circuit 24 and logic circuit 25 described in FIGS. 2 and 3.

In FIG. 4, the signal SO represents the input audio signal at 8
1 is the output of the comparator 15, 82 is the Q output of the monostable multivibrator 16, and 82' is the waveform shaping circuit 16.
33 is the output of the monostable multivibrator 16, 84 is the output of the Nantes gate 18, 85 is the output of the monostable multivibrator 19, and 86 is the 2rfi signal from the syllable detection circuit 24. gate 17
The output of each is shown.

The input audio signal is as shown in SO.

It exhibits waveform parts such as a part x where the amplitude is flat, a part Y where the imaging width is intermittently interrupted, and a part X' where the intervals between the breaks are small but are more continuous than Y. In this embodiment, the X and X' portions are determined to be musical tone parts, and the Y portion is determined to be a voice part.

Based on this, the comparator 15 outputs a pulse every time the amplitude of the input audio signal exceeds a predetermined level. Therefore, the signal S1 becomes a pulse train signal that is continuous or interrupted in a burst shape corresponding to each cycle waveform of the input audio signal. The pulse train portion corresponds to a portion where the input audio signal has an amplitude greater than a predetermined level.

Next, since the monostable multivibrator 16 has a metastable period set based on the maximum frequency of the input audio signal, it exhibits a high level during the period when the pulse train of the signal S1 continues, and a low level during the period when no pulse occurs. The resulting signal S2 is derived as the Q output. The 1-page output S3 is a signal obtained by inverting 82. Furthermore, the signal 82' is
This is a pulse train that detects the rising edge of the signal S2.

On the other hand, the output S4 of the Nandt gate 18 becomes the same signal as 82' if a fluctuation part whose amplitude is interrupted at an interval longer than the metastable period of the monostable multivibrator 19 occurs, but like the X' part, Monostable multivibrator 19
If the pulses corresponding to the first part occur at intervals shorter than the metastable period of the monostable multivibrator 19
The amplitude piece and peripheral part after inverting are not detected. thus,
A binary signal 86 is obtained from the Nant gate 17, which changes to a high level and a low level in response to an amplitude fluctuation part that is longer than a certain time width and a continuous part of the amplitude.

Next, the binary signal generated as described above enters the fall detection circuit 31. In FIG. 5, the same signals as in FIG. 4 are given the same symbols. S7 is the output of the rising edge detection circuit 31, and 88 and 89 are the flip 70 knobs 32c, respectively.
, 32b, S10 the output value of the counter 33, S11 the output of the comparator 35, S12 the output of the comparator 36, S13 the output of the AND gate 43, S14 the output of the AND gate 44, S15 816 indicates the output of the knot circuit 45, 816 indicates the output of the knot circuit 4G, and S11 indicates the control signal of the present invention output from the flip 70 tube 42, respectively.

Now, the signal S7 output from the falling detection circuit 31 is as follows.

Since the falling edge of the binary signal is detected, the signal becomes a pulse every time an amplitude variation portion occurs. This signal S7 is input to the counter 33 and counted. In this case, counter 33 has been cleared by signal S9 from flip 70 knob 32b. Thereby, the counter 33 counts the number of amplitude fluctuation parts within a certain unit period. This is how it was counted. The count value is transferred to the 7-lip flop 34 and outputted at the timing of the signal S8.

Comparators 35 and 36 are connected to the flip-flop 34
The count value from and the register value set in each register 37 and 38 are compared. Here, the value set in the register 37 is determined based on the frequency of occurrence of an amplitude variation portion that can be determined to be a voice part. Further, the register 38 is
It is determined based on the frequency of occurrence of amplitude fluctuation parts that can be determined to be musical tone parts. Specifically, a pulse in signal $7 within a unit period.

If there is less than one, it is determined that it is a musical tone part, and if there are two or more, it is determined that it is a voice part. In FIG. 1, in the musical tone part, 0.1...1.0 are generated, and in the voice part, 4 and 3 are generated.

Now, suppose that a musical tone part is being input, and the control signal S17
Let's proceed from a state in which the state is at a high level. In the musical tone part, both the signals 815 and 316 are at a high level, and the control signal 817 is at a high level.

In the musical tone part, since the frequency of occurrence of the amplitude fluctuation part is low, the output 811 of the comparator 35 shows a low level,
The output 512 of the comparator 36 indicates a high level. The musical part changes to the voice part.

When 4 pulses in signal S7 are counted.

The output S11 of the comparator 35 changes to high level, and the output 812 of the comparator 36 changes to low level. Here, the pulse of the signal 811 is passed through the NOT circuit 45 to the signal S.
15 and enters the latch circuit, so when changing from the musical tone part to the voice part, the signal 816 remains unchanged at the input of the flip-flop 42.

815 changes to low level. Therefore, it is determined that the voice part has been input, and the control signal 817 changes from high level to low level.

Next, the operation of detecting a change from a voice part to a musical tone part will be explained.

The signal 312 is at a low level during the voice part.

Since the AND gate 43 derives an AND output of the signal S12 and the signal @S8, the pulse in the signal S8 is passed during the period determined to be a musical tone part by the comparators 35 and 36. Therefore, the output signal 313 of the AND gate 43 supplies the counter 39 with the pulse P1 in the signal 313 which is generated at a cycle of a unit period during the tone part determination period based on the signal 812. Here, since the counter 39 is loaded by the signal 814 which is the AND output of the signal S15 and the signal 316, the counter 39 is.

The pulse P1 is counted, and this count value is stored in register 4.
When the value exceeds 0, a predetermined carry signal is output and the signal 816 becomes low level.

In this way, since the next time the signal 816 switches to low level is delayed, even if the comparator 35 determines that it is a musical tone part and the signal 815 indicates a high level, there is no change in the operation of the flip-flop 42, and the control signal 81
7 remains at low level.

On the other hand, when the signal 816 becomes low level, since the signal 315 is high level, the flip-flop 42 performs an inverting operation and switches the control signal 817 to high level.

In this way, control signal 817 is generated.

Next, the operation of the audio system that adds a sound field effect will be explained.

When the logic circuit 25 determines that the input signals (1) and (2) are musical tone parts, the control signal 817 is set to a high level.

The switching circuit 22 switches swi and SW2 to a conductive state,
SW3 and SW4 are switched to a non-conducting state. This results in
Input signals (original signals) amplified by the front speakers are supplied to the sound field effect circuit 23. In this way, the sound field effect output from the rear speakers is strongly influenced by the sound field effect.

When it is determined that the input signals ■ and ■ are voice parts, the control signal 11 changes to a low level, SW3 and SW4 become conductive, and SWl and SW2 become non-conductive. Therefore,
In this case, the output from the difference signal generation circuit 21 enters the sound field effect circuit 23.

The difference signal generation circuit 21 cancels out the in-phase signals and derives the signals having one phase difference as the difference signal output of the input signals (1) and (2). Input signal for stereo transmission■.

In (2), the audio signals of the presenter, etc. are transmitted in the same phase so that they are localized to the center of the two left and right speakers in the reproduction mode, and the cheering of the audience is transmitted in the phase ()Y. Therefore, the audio signals of the presenter and the like are canceled out by the difference signal generation circuit 21 and do not appear at the output terminals c and d. Furthermore, the audience's cheers appear at the output terminals c and d, and are processed by the sound field effect circuit 23.

In this way, even in the case of an audio source in which the voice of the presenter and the cheering of the audience are mixed, regardless of the state of the switching circuit 22, the sound field effect is not applied to the voice of the presenter, but the sound field effect is applied to the cheering of the surrounding people. This makes it possible to control the amount of time required.

Therefore, if such a difference signal generation circuit 21 is used, even if the content of the audio signal is determined incorrectly.

You can create a natural sound field effect.

FIG. 6 is a circuit diagram showing an embodiment of the difference signal generating circuit 21.

In this embodiment, a difference signal generation circuit 51 having the same configuration as that in FIG.
In addition, band-removal filters 52 and 54 are provided that bypass this difference signal generation circuit 51. These band elimination filters 52 and 54 have frequency characteristics set so as to remove voice band components. Then, the output of the difference signal generation circuit 51 and the output of the band-rejection filter 52.54 are added by an adder 53.55.

It is designed to be led out to each output terminal c and d.

According to this configuration, the sound field effect circuit 23 can process the in-phase components of the input signals (1) and (2) and the signals outside the audio signal band to apply a sound field effect, resulting in a more natural sense of reality. can get.

Further, the audio signal can be clearly heard by the output signals (1) and (2).

Note that the sound field effect control according to the present invention may be performed at the stage of digital signals as in each of the above embodiments, or may be performed at the stage of analog signals. If you want to do it in an analog way,
An analog integrated circuit is used as the sound field effect circuit.

Furthermore, although the explanation has been made for the case where the input audio signal is a two-channel signal, the same applies to the case where the input audio signal is a multi-channel signal.

The present invention can be applied by outputting the difference component between two signals that include signals in the same phase.

Furthermore, even when using a sound field effect circuit that arbitrarily increases the sound field effect output signal regardless of the number of input audio signals,
produces a similar effect.

[Effects of the Invention] As explained above, according to the present invention, a natural sound field effect can be applied without creating a large difference in the sound field effect between the voice part and the musical tone part.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the automatic sound field effect control device according to the present invention, and FIGS. 2 and 3 are specific circuit diagrams explaining the configuration of FIG. 1 in detail. 4 and 5 are timing charts explaining the invention in detail, FIG. 6 is a circuit diagram showing another embodiment of the invention, and FIG. 7 is a block diagram explaining a conventional sound field effect control method. It is. 21...Left signal creation circuit, 22...Switching circuit, 23
...Sound field effect circuit, 24...Syllable detection circuit, 2
5...Logic circuit. 52, 54...Band elimination filter.

Claims (2)

[Claims] (1) A difference signal creation circuit that outputs the difference between two signals for stereo transmission among audio signals consisting of multiple channels, a line that passes the two signals as they are, and determines the voice part and musical tone part of the audio signal. determining means; a switching circuit for selecting either the output from the difference signal generation circuit or the output from the line depending on the output of the determining means; and adding a sound field effect to the output from the switching circuit. A sound field effect automatic control device comprising a sound field effect circuit. (2) A claim characterized in that the difference signal generation circuit includes a band elimination filter that removes a voice band component from the two signals, and an addition means that adds the output from this filter and the difference output. Item 1. The sound field effect automatic control device according to item 1.