JPH03280699A - Sound field effect automatic controller - Google Patents

Abstract

PURPOSE:To eliminate noise due to changeover between an audio part and a musical sound part by mixing two signals in stereo transmission and a differential signal and outputting the mixed signals so that the mixture ratio is changed complimentarily in response to the lapse of time from a point of time when the audio part and the musical sound part of an audio signal are switched. CONSTITUTION:A differential signal generating circuit 15 outputs a difference (c) between two signals a, b in stereo transmission in audio signals of plural channels. A mixing circuit 21 mixes the two signals a, b and the output (c) from the differential signal generating circuit 15 and outputs the result so that the mixture ratio is changed complimentarily in response to the lapse of time from a point of time of changeover of the result of decision outputted from a decision means 19 deciding the audio part and the musical sound part of an audio signal are switched. Then a sound field effect circuit 17 provides a sound field effect to an output from the mixing circuit 21. Then the mixture rate where the difference signal (c) is mixed in L, R signals changes gradually from a point of time of the changeover of the audio part and the musical sound part thereby preventing generation of noise.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) This invention is a sound field effect circuit that adds 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 darkening sound field effect from appearing on audio parts.

(Prior art) Technological progress in the field of audio today is remarkable.
From monaural to stereo, and from analog to digital, there has been a shift in technology to get closer to the original sound.Furthermore, in recent years, music has been processed to suit the listener's tastes, and originality has been improved. There is an increasing demand for technology for forming a certain sound field.

To meet these demands, there is, for example, a sound field effect circuit called a surround system.

As shown in FIG. 9, the surround system is one in which a sound field effect circuit is added to the audio system.

In FIG. 9, reference numeral 1 denotes an audio input terminal for inputting audio signals from a CD, tape recorder, etc. This audio input terminal 1 is connected to a low-pass filter 2, and the livestock signal applied to the audio input terminal 1 passes through the low-pass filter 2 and is converted into a digital signal by an A/D converter 3. The digital signal converted by the A/D converter 3 is input to the sound field effect circuit 4, and through digital processing including delay processing, reverberant sound signals heard from the front and rear of a concert hall or other performance venue are processed. It is added and output. These digital original signals and reverberant sound signals are each D/A
The signal is converted into an analog signal by a converter 5.6, passes through a low-pass filter 7.8 and an amplifier 9.10, and is amplified by the left and right speakers 11 on the front side and the left and right speakers 12 on the rear side.

By adding the above-mentioned sound field effect circuit to the audio system, listeners can experience a sense of presence as if they were in a concert hall or sports venue.

By the way, in the above sound field effect circuit, when creating an atmosphere equivalent to a concert hall, for example, the reverberation time is 1.
The reverberation sound is generated for about 1 to 2 seconds, but the problem is that the reverberation 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.

Furthermore, in order to create a sense of presence equivalent to that of a sports venue, the sound field effect circuit 4 generates an echo sound at about 100m5ec, for example, and the sound echoes not only from the cheering of the audience, but also from the voices of the presenters and commentators. There was a sound.

In order to solve the above-mentioned problem, as shown in FIG. 9, a syllable detection circuit 13 generates a binary signal indicating which part it is, based on the characteristics of the voice part and musical tone part in the audio signal. However, a circuit was proposed in which a logic circuit 14 determines whether an audio signal is a music part or a human voice part based on this binary signal (for example, Japanese Patent Application No. 163448/1983).

That is, in FIG. 9, the output of the logic circuit 14 becomes a control signal that controls the operation of the sound field effect circuit 4, and this control signal causes the sound field effect circuit 4 to add a sound field effect during the southeast part. During the audio part, the original signal without any sound field effects is output.

In addition, in the case of a two-channel signal such as a stereo signal, focusing on the fact that audio signals are mainly recorded or transmitted as two-channel in-phase components, the L signal A difference signal between the R signal and the R signal is generated, and this and the R signal are used as the voice part and the musical tone part, respectively.
There is an example in which a sound field effect is applied to a signal that is selectively output in accordance with the result of the determination.

In FIG. 10, the input signals (1) and (2) led to the input terminals TPII and TP12 are a stereo 1 signal and an R signal, respectively. Input signals ■ and ■ are output terminals TP21. T
The output signals ① and ② are directly derived from P22, and a stereo output is obtained.

In addition, the input signals ■ and ■ are input to the difference signal generation circuit 15 (
a, b) and the in-phase signal component is removed from the LR difference signal (
c, d), and these difference signals C1d and input signals a, b
are input to a switching circuit 16 consisting of analog switches SW1 to SW4, and outputs e and f are obtained by either the difference signals c and d or the input signals a and b. A sound field effect by a sound field effect circuit 11 is added to these signals e and f.

Similar to FIG. 9, the syllable detection circuit 18 and the logic circuit 19 determine the binary signal from the syllable detection circuit 18 in the logic circuit 19 to generate a control signal for controlling the switching circuit 16. .

According to the circuit shown in FIG. 10, sufficient sound field effects can be added to the audience's cheers and the southeast part while maintaining the clarity of the host's announcement and the actors' lines.

However, according to the above-mentioned sound field effect device, when switching between the audio part and the southeast part, the change becomes noise and is amplified from the speaker, and the noise may be heard by the listener. That is, when the phase difference between the in-phase component signal and the anti-phase component signal is large, there is an inconvenience that a popping sound appears at the time of the above-mentioned switching.

(Problems to be Solved by the Invention) As described above, the conventional switching method shown in FIG. 10 has the disadvantage that noise appears when switching between the audio part and the southeast part, and the noise is audible to the listener. Ta.

SUMMARY OF THE INVENTION An object of the present invention is to provide an automatic sound field effect control device that eliminates noise caused by switching sound field effects in response to switching between a voice part and a musical tone part, and provides a natural sound field effect.

[Structure of the Invention] (Means for Solving the Problems) The first invention provides a difference signal generation circuit that outputs a difference between two signals for stereo transmission among audio signals consisting of a plurality of channels, and A line to pass through,
a determination means for determining a voice part and a musical tone part of the audio signal, and further for mixing each of the two signals and an output from the difference signal creation circuit, and outputting the mixing ratio from the determination means. The apparatus includes a mixing circuit that outputs an output that changes complementary with the passage of time from the point in time when the result is switched, and a sound field effect circuit that adds a sound field effect to the output from the mixing circuit.

A second aspect of the present invention is characterized in that the mixing ratio of the mixing circuit changes logarithmically in a complementary manner in accordance with the lapse of the spacing from the time point when the judgment result output from the judgment means changes.

(Function) According to the above configuration, the mixing ratio of the difference signal and the R signal changes temporarily from the time of switching between the musical tone part and the voice part, so that noises such as bouncing sounds are generated. will not occur.

(Example) Hereinafter, the present invention will be explained in detail with reference to illustrated examples.

FIG. 1 is a block diagram showing an embodiment of an automatic sound field effect control device according to the present invention.

In FIG. 1, the input signals ■ and ■ are two-channel audio signals transmitted by stereo transmission, and the input terminals TPI1
．． Applied to TP12. These input signals ■, ■ are
As output signals ■ and ■ to the front speakers ~output terminal TP21. It is directly output from the TP22 and input to the syllable detection circuit 18, and is also input to the A/D conversion l52.
It is also input to the difference signal generation circuit 15 via 0.

The difference signal generation circuit 15 inputs inputs a and b corresponding to the input signals ■ and ■ to a subtracter, and derives the difference signal as an output C. Output C from the difference signal generation circuit 15 and signals a and b from the A/D converter 20 are input to a mixing circuit 21.

The mixing circuit 21 is composed of two independent product-sum operation sections. That is, the mixing circuit 21 includes multipliers mO, ml
and an adder A1, and a multiplier mo
, m2 and a second product-sum sieve section consisting of an adder A2. Here, the input signal a to the difference signal generation circuit 15 is input to the multiplier m1, and the output of the multiplier m1 is led to the first input terminal of the adder A1. multiplier m
2 receives the input signal of the difference signal generating circuit 15, and the output of the multiplier m2 is supplied to the first input terminal of the adder A2. The output C from the difference signal generation circuit 15 is input to the multiplier mO, and the output from the multiplier mO is input to the adder A.
1 and A2 are supplied to each second input terminal. Adder A1
The outputs of A2 and A2 become input signals e and f to the sound field effect circuit 17, respectively.

The sound field effect circuit 17 is, for example, a digital audio processor that adds a surround effect, and is connected to the short output terminals TP13. through the D/A converter 22. Sound field effect output signals ■ and ■ are respectively derived from TP14.

As will be described later, the syllable detection circuit 18 utilizes the fact that the voice part and musical tone part each have characteristic parts, and outputs a binary signal corresponding to each part.

The 2fii signal from the syllable detection circuit 18 is input to the logic circuit 19. The logic circuit 19 generates a determination output that determines the switching from the voice part to the musical tone part and the transition from the musical tone part to the voice part. The syllable detection circuit 18 and the logic circuit 19 constitute a determining means for determining whether the part is a musical tone part or a voice part.

The multiplication coefficient generation circuit 23 is connected to the logic circuit 1 as described later.
Based on the output that determines the switching between the musical tone part and the audio part from No. 9, input terminal TP11. A multiplication coefficient is generated to control the mixing ratio of the signals (1) and (2) from the TP 12 and the output signal C from the difference signal generation circuit 15.

Two types of multiplication coefficients are provided corresponding to the two systems of product-sum calculation units. One multiplication coefficient 01 controls multipliers m1 and m2 of the mixing circuit 21, and one multiplication coefficient C2 controls multiplier mO.

Next, a specific circuit of the syllable detection circuit 18 will be explained with reference to FIG.

This circuit shows a circuit that determines one of the input signals (2) and (2). TP3 supplies input signal 1 or 2 to one input terminal of analog comparator 25. The other input terminal of the analog comparator 25 is connected to a trimmer component such as a variable resistor, for example, with a threshold voltage for detecting a fluctuation part of the envelope in order to distinguish between a musical tone part and a voice part in the input audio signal. It is set and applied by. As a result, the analog comparator 25 obtains a signal that distinguishes between a flat part where the amplitude of the input audio signal is greater than the threshold voltage and a fluctuating part where the amplitude is small.

The output of the analog comparator 25 is input to a retrigger type monostable multivibrator 26. This monostable multivibrator 26 has two output terminals Q and U.
is taken out, one output Q is supplied to one input terminal of the Nandts gate 28 via a waveform shaping circuit 26a constituted by a diode and a capacitor, and the output U is supplied to one input terminal of the Nandts gate 28. . The output of the Nant gate 28 is supplied to a retrigger type monostable multivibrator 29, and this monostable multivibrator 2
9 feeds back the output Q to the other input terminal of the Nandt gate 28. With the monostable multivibrator 29 having this configuration, it is possible to obtain a binary signal in which all the fluctuation parts are detected, regardless of the time width of the fluctuation parts of the input audio signal. This binary signal also enters the other input terminal of the Nant gate 27 and is logically compared with the output from the monostable multivibrator 26. Monostable multivibrator 29 is monostable multivibrator 2
A stable period longer than 6 is set, so that the output of the Nant gate 27 represents a binary signal in which only the fluctuation part longer than a certain period of 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 19 will be explained with reference to FIG.

In FIG. 3, the terminal TP5 is the terminal T in FIG.
A binary signal from P4 is derived. The binary signal from the terminal TP5 is sent to the flip-flop circuits 31a, 31b 1
and an AND gate 31C. In this fall detection circuit 31, each flip-flop circuit 31a, 31b is operated by a clock signal from a low clock generator 30.

The detection pulse indicating the fall of the binary signal is detected by the AND gate 3.
It is derived from 1C and enters the first) counter 33.

The counter 33 supplies a count output to comparators 35 and 36 via a knob 70 and a knob 34 with a latch function. These] comparators 35 and 36 compare the register values from the registers 37 and 38, which have been set in advance, with the count value of the flip-flop 34, respectively. The comparison result of the comparator 35 is the not circuit 4.
5 respectively to the latch circuit 41 and the AND gate 4
It is input to one terminal of 4.

The comparison result of the comparator 36 is input to the counter 39 via an AND gate 43. Above counter 3
9 counts the output of the comparator 36 input via the AND gate 43, using the register value set in the register 40 as an overflow value. Therefore, when the register value set in the output register 40 of the comparator 36 is exceeded, the counter 39 supplies an output as a carry signal to the latch circuit 41 and the other terminal of the AND gate 44 via the NOT circuit 46. .

On the other hand, counter 32a1 flip-flop 32b32
The circuit constructed by c constitutes a timing signal generation circuit that operates in response to a clock signal from the clock generator 3o. This timing signal generation circuit sends a signal that clears the counter 33 to the seven lip-flop 32.
From b, the signal to be latched by the flip-flop 34 is set to 7.
The signals are outputted from the lip 70 and the tube 32c and supplied to a predetermined circuit.

The audio signal is divided into predetermined unit sections by the outputs of these flip-flops 32b and 32C.

Note that the output of the flip-flop 32c is also supplied to the other input terminal of the AND gate 43. The stock generator 30 also drives counters 33 and 39.

Thus, the latch circuit 41 outputs outputs based on the comparator 35 and the counter 39, respectively, via the flip-flop 42 to the terminal TP6. This terminal TP6
The signal derived from this is input to the multiplication coefficient generation circuit 23 shown in FIG.

Further, a configuration example of the multiplication coefficient generation circuit 23 will be explained with reference to FIG.

The judgment output generated by the logic circuit 19 is input to the latch circuit 53 from the terminal 51, and further to the latch circuits 54 and 55.
The clock from the clock generator 52 is delayed by three clocks. Output of latch circuit 53 and latch circuit 5
The outputs of 4 are input to exclusive OR gates 55, respectively. The exclusive OR gate 55 forms a signal that exhibits a pulse for one clock cycle from the rise of the clock after the timing at which the level of the determination output changes. This exclusive OR output is input to the counter 59 as a reset signal.

Counter 59 is a multiplication coefficient CI according to the present invention.

This circuit generates a signal that is the source of C2, counts the clock from the clock generator 52, and generates a carry signal at a certain overflow value to enable the count.

The output of the counter 59 is input to the second input terminal group of the selector 57 and the first input terminal group of the selector 58 via the latch circuit 61, and is input to the first input terminal group of the selector 57 via the knot circuit 62. , are input to the second input terminal group of the selector 58. These selectors 57 and 58 selectively output the signals of the first input terminal group and the first input terminal group according to the output of the latch circuit 56, and
．． 64 and the multiplication coefficient 01°C2 are respectively derived.

Note that the output of the counter 59 has an n-bit configuration, and the latch circuit 61 outputs these n bits to the selector 57 .
58 and a NOT circuit 62, respectively, and the NOT circuit 62 inputs n-bit outputs obtained by inverting the n-bits from the counter 59 to the selectors 57 and 58, respectively. Further, the latch circuit 61 receives the output of the exclusive OR gate 55 and the output from the clock generator 52 via an AND gate 60 as latch control.

Thereby, the latch circuit 61 latches the reset output of the counter 59 and then successively latches the counter outputs whose clock timing changes.

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

First, FIGS. 5, 6, and 7 show the syllable detection circuit 18 and logic circuit 1 explained in FIGS. 2, 3, and 4.
9 is a timing chart illustrating the operations of the multiplication coefficient generation circuit 23 and the multiplication coefficient generation circuit 23.

In FIG. 4, the signal SO is the input audio signal S
l is the output of the analog comparator 25, S2 is the output Q of the monostable multivibrator 26, S2' is the output of the waveform shaping circuit 26a, s3 is the output port of the monostable multivibrator 26, and S4 is the output of the Nantes gate 28. output,
S5 is the output signal of the monostable multivibrator 29, and S6 is the output signal of the syllable detection circuit 18, which is the Nant gate 2.
7 output signals are shown respectively.

As shown in SO, the input audio signal has waveform parts such as a part X where the amplitude is flat, a part Y where the amplitude is intermittently interrupted, and a part X' where the interruption interval is small but is more continuous than Y. present. The syllable detection circuit 18 determines that the X and X' portions are musical tone parts, and the Y portion is determined to be a voice part.

The analog comparator 25 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 continues in a burst shape or is interrupted in response to each cycle waveform of the input audio signal. And the pulse train part is
Corresponds to a portion where the input audio signal is greater than a predetermined level.

Next, since the monostable multivibrator 26 has a quasi-stable 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 output Q. Then, the U output S3 becomes a signal obtained by inverting S2. Further, the signal 32' is a pulse train that detects the rising edge of the signal S2.

On the other hand, the output S4 of the Nant gate 28 becomes the same signal as S2' when a fluctuation part in which the amplitude is interrupted at an interval longer than the metastable period of the monostable multivibrator 29 occurs, but the output S4 of the Nant gate 28 becomes the same signal as S2'. Stable multivibrator 29
If the pulses corresponding to the first part occur at intervals shorter than the metastable period of the monostable multivibrator 29
is reversed, and the later amplitude fluctuation opening is not detected. In this way, a binary signal S6 is obtained from the Nant gate 27, which changes to a high level and a low level corresponding to an amplitude fluctuation part longer than a certain time width and a continuous part of amplitude.

The binary signal S6 generated in this manner is input to the fall detection circuit 31 of the logic circuit 19.

In FIG. 6, the same signals as in FIG. 5 are given the same symbols. S7 is the output of the fall detection circuit 31, S8. S
9 represents each output of the flip-flops 32C and 32b.
10 is the output of the counter 33, 811 is the output of the comparator 35, 312 is the output of the comparator 36, S
13 is the output of the AND gate 43, S15 is the output of the NOT circuit 45, S16 is the output of the NOT circuit 4G, S1
7 is an output signal of the logic circuit 19, which is an output signal of the flip-flop 42.

Now, since the signal S7 output from the fall detection circuit 31 detects the fall of a binary signal, it becomes a signal that exhibits a pulse every time a vibration fluctuation section occurs.

This signal S7 is input to the counter 33 and counted by the counter 33. In this case, the counter 33 receives the signal S9 from the flip-flop 32b.
It has been cleared by. Thereby, the counter 33 counts the number of amplitude fluctuation parts within a certain period of imperial reign. The count value thus counted is transferred to the 7 lip flop 34 at the timing of the signal S8.
is transferred to and output.

Comparators 35 and 36 are the flip-flops 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, if the number of pulses in the signal S7 within a unit period is one or less, it is determined that it is a musical tone part.

In the figure, in the musical tone part, 0, 1, . ..., 1. O
This occurs as 4 and 3 in the audio part.

Now, suppose we are inputting a musical tone part and the control signal 317
Let's proceed from a state in which the state is at a high level. In addition,
In the musical tone part, both signals 315 and 316 are at high level, and control signal 817 is at low level.

In the musical tone part, since the amplitude fluctuation part occurs less frequently, the output 811 of the comparator 5 shows a low level,
The output 812 of the comparator 36 indicates a high level. When the musical tone part changes to the voice part and four pulses in the signal S7 are counted, the output 811 of the comparator 35 goes high, and the output 812 of the comparator 36 goes high.
changes to low level. Here, the pulse of the signal 811 is inputted to the latch circuit 41 as a signal 815 via the knot circuit 45, so when changing from the musical tone part to the voice part, the input signal of the flip-flop 42 is
While the signal 816 remains unchanged, the signal 815 changes to low level. Therefore, it is determined that the voice part has been input, and the control signal Sj7 changes from low level to high level.

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

The signal 812 is at a low level during the voice part. Since the AND gate 43 derives an AND output 813 of the signal 812 and the signal s8, the comparators 35 and 36
Accordingly, a pulse in the signal S8 is passed during a period determined to be a musical tone part. Therefore, the signal @s13 output by the AND gate 43 is the signal S1 generated at the cycle of the unit period in the voice part determination period based on the signal 812.
The pulse P1 of 3 is supplied to the counter 39. Here, the counter 39 is put into a loaded state by the signal 814 which is the AND output of the signal 815 and the signal S16, so the counter 39 counts the pulse P1, and when this count value exceeds the value of the register 40, a predetermined A carry signal is output to set the signal 516 to low level.

In this way, the timing at which the signal 816 switches to low level is delayed, so even if the comparator 35 determines that it is a musical tone part and the signal S15 indicates a high level,
There is no change in the operation of the flip-flop 42, and the control signal 817 remains at a high level.

On the other hand, when the signal 816 becomes low level, since the signal @S15 is high level, the flip-flop 42 performs an inverting operation and switches the control signal S17 to low level.

In this way, the control signal S17 is generated, and this control signal S17 is input to the multiplication coefficient generation circuit 23.

In FIG. 7, the same signals as in FIG. 6 are not given the same symbols. S17 is an output of the logic circuit 19 and is a control signal indicating whether the part is a musical tone part or a voice part. For example, the musical tone part is at a low level and the voice part is at a high level.

Further, the determination change interval (to −t4, t
4/~t8) is at least 75m5. This is because the burst-like silence period that occurs in sentences, phrases, and consonants, such as lines in voice parts and announcement speeches, is said to be approximately 75 m5.In the ethical circuit (see Figure 3), This is because such silent sections are not subject to determination. If 8 per minute
75 per character even if you speak at a fast speed of 00 characters.
It takes m5. Sentences, phrases, and consonants are formed by stringing these letters together, so changes actually occur at intervals longer than 75m5. Signal 818 is the output clock of the clock generator 52, 819 is the output signal of the latch circuit 56, 820 is the output signal of the exclusive OR gate 55, 821 is the output signal of the OR gate 60, and 822 is the output signal of the counter 59. 823 is the output of the latch circuit 61, S24 is the output of the NOT circuit 62, 825 is the waveform of the multiplication coefficient 02 output from the multiplication coefficient generation circuit 23, 82
6 shows the waveform of the multiplication coefficient C1 output from the multiplication coefficient generation circuit 23, respectively.

Signal 817 is synchronized by clock pulse s18 and becomes signal 819 delayed by three clocks. Signal S19
The rising time t2 is determined by the clock 81 from the judgment change point 10 from the musical tone part to the voice part in the judgment output S17.
There is a delay of 3 clock periods from the minute time α within one period of 8. Further, the output signal 820 of the exclusive OR gate 55 exhibits a high level pulse P2 for one cycle period from the rising edge of the clock (tl) after the determination change point to of the musical tone part and the voice part. The counter 59 is reset by the pulse P2 of the output signal 820, and the initial value is set to rOJ. The output value S22 of the counter 59 is held in the latch circuit 61. There is a delay of one clock period between the output S23 of the latch circuit 61 and the signal 822.

As mentioned above, the output 823 of the latch circuit 61 is rOJ~
If the signal changes stepwise up to "7", the signal 824 output from the knot circuit 62 will change from "7" to "0".
It gradually changes down to . The selector 57 receives the signal S
The signals of the second input terminal group are selectively output during the high level period of 19, and the signals of the second input terminal group are selectively output during the low level period. Therefore, the signal 819 derived from the control signal 817
In the section of the voice part where the signal changes from low level to high level, the multiplication coefficient 02 is 1, the multiplication coefficient 02 is in the up form as shown at 325, and the multiplication coefficient C1 is in the down form as shown at 826.

Note that the maximum value "7" of the signal 325.826 means the amount of attenuation or the attenuation step width, so the larger the value, the smoother the switching characteristics. In reality, the detection limit for the overall attenuation and auditory level change is 0.2 (dB) (this value is given in the reference book, ``Handbook of Sensory Perceptual Psychology'', p. 709, published by Seishin Shobo). It may be changed by the step width (as described).

As the control signal 817 changes from the voice part to the musical tone part at time t4, the counter 59 is reset at time t5, α time after t4, and the output value becomes "0".

The counter 59 then outputs a signal S22 that increases stepwise from "0" to "7" at time t6 after three zeros have passed since time t5.

Therefore, the output of the latch circuit 61 is rOJ from time t6.
The signal increases step by step to 7.

As mentioned above, the output 823 of the latch circuit 61 is rOJ~
If the signal changes up to "7", the knot circuit 6
The signal S24 output from 2 changes down from "71" to "0". Since the signal S19 is at a low level, the selector 57 selectively outputs the signals of the first input terminal group, and the selector 58 selectively outputs the signals of the first input terminal group. Therefore, in the transition period from the high level to the musical tone part where the signal 819 derived from the request signal @S17 changes from high level to low level, the multiplication coefficient 02 becomes a down-type signal as shown at 825, and the multiplication coefficient 01 becomes a down-type signal as shown at 826. The signal becomes an up-type signal as shown in .

Furthermore, if the attenuation amount is 60 (dB), the number of bits n is 1
It is sufficient if it is about 0, and in that case, 102 clocks are required from time tO to t3. The period of the clock pulse from the clock oscillator 52 is set to approximately 22 μS (
44,1ktlZ), t3~to=23iS. Therefore, the maximum change width from t4 to 10 is 75
The stepping operation ends in a sufficiently shorter period than ilS.

In this way, the multiplication coefficient CI whose up and down changes are complementary
, C2 of the multiplier m1 of the mixing circuit 21.

When m2 and mO are controlled, in the interval from t2 to t2 when the musical tone part changes to the voice part, the attenuation amount for the signals a and b is the minimum, and the attenuation amount for the difference signal C is the maximum. The sound field effect is applied to the output where the amount of attenuation for the signals a and b is maximum and the amount of attenuation for the difference signal C is the minimum. Also, 16~t changes from the voice part to the musical part.
7 are synchronized, so in each sampling period, the output with the maximum attenuation for signals a and b and the minimum attenuation for difference signal C has the minimum attenuation for signals a and b, and the difference The sound field effect is applied to the output where the amount of attenuation for signal C changes to the maximum.

Below, the operation of the audio system that adds the sound field effect will be explained in detail.

The input signals ■ and ■ are input to the syllable detection circuit 18,
Binary code S6 depending on the musical tone part or voice part
Output. Logic circuit 1 that takes in this binary code S6
When the control signal 9 determines that the input signals ① and ② are voice parts, it supplies the control signal 517 to the multiplication coefficient generation circuit 23 at a high level. As a result, the multiplication coefficient 01 of the multiplication coefficient generation circuit 23 gradually becomes rOJ from the maximum value, and the multiplication coefficient C2 gradually becomes the maximum value from 0. On the other hand, since the clock pulse 818 from the multiplier generation circuit 52 of the multiplication coefficient generation circuit 23 is synchronized with the sampling signal of the A/D converter 20, the clock pulse 818 is sent to the multipliers mO to m2 of the mixing circuit 21 for each sampling. Multiplication is performed. Therefore, the output terminals e and f of the mixing circuit 21 receive a signal that changes so that the proportion of the difference signal C from the difference signal generation circuit 15 gradually becomes larger than the output signals a and b of the A/D converter 20. is output. Finally, the multiplier ml of the mixing circuit 21,
m2 becomes non-conductive, multiplier mO becomes conductive, and during the voice part, in-phase signals such as lines and announcements are not supplied to the sound field effect circuit 17, and only the difference signal is supplied.

On the other hand, when the logic circuit 19 again determines that it is a musical tone part, the output C1 of the multiplication coefficient generation circuit 23 is "0".
”, the output C2 gradually reaches the maximum value, and its output C2 gradually reaches rOJ from the maximum value. In addition, the multiplication coefficient generation circuit 23
Since the clock pulse S18 from the clock generation circuit 52 is synchronized with the sampling signal of the A/D converter 20, the multiplier mO~ of the mixing circuit 21 is generated for each sampling.
Multiplication is performed in m2. As a result, the mixing circuit 21
A signal that gradually changes from the output signal C of the difference signal generation circuit 15 to the output signals a and b of the A/D converter 20 is output to the output terminals e and f of. Finally, the multipliers ml and m2 of the mixing circuit 21 become conductive, and the multiplier mO
becomes non-conductive, and signals a and b are supplied to the sound field effect circuit 17 during the musical tone part.

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, it is possible to perform control such that the sound field effect is not applied to the voice of the presenter and the sound field effect is applied to the cheering of the surroundings.

FIG. 8 is a block diagram showing another example of the configuration of the multiplication coefficient generating means.

As shown in FIG. 1, the multiplication coefficient generation circuit 23 uses the same multiplication coefficient as the sidewalk value obtained by the binary counter 59 as shown in FIG. The multiplication coefficients may be obtained by using ROMs 101 and 102 that store tables containing multiplication coefficients obtained by logarithmically transforming the outputs CI and C2 of the coefficient generation circuit 23.

Here, multiplication coefficient values are written in the ROMs 101 and 102 at equal intervals on a logarithm along the address value, so that when the address is selected, the multiplication coefficient is output as data. The outputs CI and C2 of the multiplication coefficient generation circuit 23 are input as address inputs of the ROM 101102. This allows ROM 101.10
2, the multiplication coefficients CI' and C2' are derived, so
These are multiplied by the multiplier m1 of the mixing circuit 21. What is necessary is to give it to m2.

In this way, an attenuation curve with steps of, for example, 0.2 [dB] or an arbitrary attenuation curve can be easily obtained. Further, since the number of bits of the binary counter 59 in the multiplication coefficient generation circuit 23 and the coefficient word length of the multipliers mO to m2 in FIG. 1 can be set to different numbers, more accurate signal processing is also possible.

Moreover, the circuit configuration for doing this also becomes simple. Note that depending on the processing speed, the ROMs 101102 may be used in multiplexed form.

In addition, according to the method of generating multiplication coefficients, the period of the clock pulse used in the multiplication coefficient generation circuit 23 in the embodiment shown in FIG. It may also be a periodic signal. In that case, when the multipliers mO to m2 calculate the sampling values (signals) and coefficient values, it is sufficient to perform processing such that the coefficient values do not change during the same sampling.

Furthermore, since digital processing is used to realize the above multiplication coefficient generation processing method, software processing by a signal processor or a microcomputer can be used.

Although the sound field effect control according to the invention described above is performed at the stage of digital signals as in each of the above embodiments, it may also be performed at the stage of analog signals. When performing analog sound field effect control in this way, analog ! A product circuit (such as a VCA) may be used.

Further, although the explanation has been made for the case where the input audio signal is two channels, the present invention can be applied to multi-channel signals by outputting the difference component between two signals that include signal components of the same window. .

Furthermore, even when using a sound field effect circuit in which the sound field effect output signal is arbitrarily added regardless of the number of input audio signals,
A similar effect occurs.

[Effects of the Invention] As described above, according to the present invention, it is possible to apply a natural sound field effect without creating a large difference in the sound field effect between the audio part and the musical part, and and musical tone parts can be smoothly and naturally switched.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the automatic sound field effect control device according to the present invention, and FIGS.
5, 6, and 7 are timing charts for explaining the present invention in detail. FIG. A block diagram showing another embodiment, FIGS. 9 and 10 are block diagrams showing a conventional automatic sound field effect control device. 15... Difference signal creation circuit, 17... Sound field effect circuit,
18...Syllable detection circuit, 19...Ethical circuit, 2
0...A/D converter, 21...Mixing circuit, 22...
- D/A converter, 23... multiplication coefficient generation circuit. Yuu (@Part-+-1 @P)V

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. a determining means for mixing each of the two signals and an output from the differential signal generating circuit so that the mixing ratio changes complementary with time from a point in time when the determination results outputted from the determining means are switched; 1. An automatic sound field effect control device comprising: a mixing circuit that outputs an output to the mixing circuit; and a sound field effect circuit that adds a sound field effect to the output from the mixing circuit. (2) 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. a determining means for mixing each of the two signals and an output from the differential signal generating circuit, the mixing ratio of which changes logarithmically in a complementary manner over time from a switching point in time between the determination results output from the determining means; What is claimed is: 1. A sound field effect automatic control device comprising: a mixing circuit that outputs a sound field effect as shown in FIG.