JP7270736B2 - Acoustic equipment and self-oscillation determination program - Google Patents

Description

The present invention relates to an acoustic device and a self-oscillation determination program.

Audio equipment such as analog synthesizers processes the basic waveform of the input musical tone signal using a digital filter to generate a new waveform signal that has been processed, and outputs musical tone signals with various tones. do.
For example, in the musical tone signal generator described in Patent Document 1, a filter parameter generator generates a waveform memory according to a key identification signal and a key touch response signal generated according to a keystroke operation on a keyboard, and an operation state of an operation panel. Based on the timbre information read from the , three parameters of bias, depth, and envelope necessary for generating the cutoff frequency, and the resonance value are generated. The generated cutoff frequency and resonance value are input to the filter circuit, which processes the basic waveform of the musical tone signal based on these values and outputs musical tone waveform data.

Japanese Unexamined Patent Application Publication No. 2004-4304

By the way, in such audio equipment, if the operator adjusts the resonance value and processes the basic waveform with a filter circuit, it may oscillate at a frequency unrelated to the input basic waveform. A sound with a pitch different from the keyed sound may be output loudly, resulting in a dissonant sound. This is called a self-oscillation phenomenon.
The self-oscillation phenomenon causes a problem when the pitch of the tapped key and the pitch of the dial tone are close to each other, and the loud dissonance caused by the self-oscillation phenomenon gives the listener discomfort. It is desirable not to listen to it.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an acoustic device and a program for determining self-oscillation that enable an operator to visually recognize the start of a self-oscillation phenomenon before the operator can recognize the self-oscillation phenomenon by ear. .

The audio equipment of the present invention includes filter processing means for processing a waveform of an input signal and outputting the result, adjustment operation means for urging an operator to adjust a control parameter of the filter processing by the filter processing means, and filter processing means. input signal acquisition means for acquiring an input signal to the processing means; output signal acquisition means for acquiring an output signal filtered by the filtering means; frequency components of the acquired input signal and the acquired output signal; self-oscillation determination means for comparing frequency components and determining whether or not self-oscillation has occurred based on the synchronous state of the input signal and the output signal; and self-oscillation has occurred by the self-oscillation determination means. a self-oscillation notification means for notifying the outside when it is determined that

A computer-readable program for determining self-oscillation of the present invention causes a computer to function as the above-described audio equipment.

1 is a block diagram showing the structure of an analog synthesizer as an acoustic device according to an embodiment of the present invention; FIG. 5 is a graph for explaining the self-oscillation phenomenon in the embodiment; 5 is a graph for explaining the self-oscillation phenomenon in the embodiment; 5 is a graph for explaining the self-oscillation phenomenon in the embodiment; 4 is a block diagram showing the structure of self-oscillation determination means in the embodiment; FIG. 4 is a graph for explaining generation of sampling clocks in the embodiment; 6 is a graph for explaining sampling of output signals in the embodiment; 4 is a flow chart for explaining the action of the embodiment; 6 is a flow chart for explaining a second embodiment of the present invention; 4 is a flow chart for explaining the embodiment;

[1] Overall Configuration An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an analog synthesizer 1 as an acoustic device according to one embodiment of the present invention.
The analog synthesizer 1 is a device that processes a generated basic waveform by filtering, amplifies the processed output waveform, and outputs it as an acoustic signal. The analog synthesizer 1 includes a VCO (Voltage Controlled Oscillator) 2, a VCA (Voltage Controlled Amplifier) 3, a VCF (Voltage Controlled Filter) 4, an adjustment operation means 5, an input signal acquisition means 6, an output signal acquisition means 7, and a self-oscillation determination means. 8 and self-oscillation notification means 9 .

VCO2, VCA3, and VCF4 are voltage-controlled, and although not shown in FIG. 1, are controlled by parameters generated by circuits such as an envelope generator, LFO (Low Frequency Oscillator), UI such as keyboard, and sequencer.
The input signal acquisition means 6, the output signal acquisition means 7, the self-oscillation determination means 8, and the self-oscillation notification means 9 are configured as a computer-readable self-oscillation determination program executed on a computer.

A VCO 2 is an oscillation circuit that generates a basic waveform used in the analog synthesizer 1 . Specifically, the VCO 2 generates various basic waveforms according to parameters generated by operating a UI such as a keyboard, for example, basic waveforms such as square waves, sine waves, triangular waves, and sawtooth waves. do. Although not shown in FIG. 1, the basic waveform can be selected by a waveform selection knob provided on the adjustment operating means 5. FIG.
VCA 3 is a circuit that adjusts the volume of sound output from analog synthesizer 1 . Specifically, the VCA 3 is based on four control parameters for the envelope generated by the envelope generator, such as attack, decay, sustain after decay, and release. Controls the time-varying output volume.

The VCF 4 as filtering means is a circuit for processing the basic waveform of the input signal by filtering the basic waveform of the input signal generated by the VCO 2 .
Specifically, the VCF 4 processes the basic waveform of the input signal based on the cutoff frequency and resonance value, which are control parameters.

The cutoff frequency is a control parameter that sets the frequency of sound that passes through the VCF 4, and is generated based on the control parameters for bias, depth, and envelope. The control parameters of the cutoff frequency are adjusted by an operator operating a cutoff frequency adjustment knob 51, which will be described later.
The resonance value is a parameter for adjusting the degree of sound interruption at a frequency cut off at the cutoff frequency, and is adjusted by the operator operating a resonance value adjustment knob 52, which will be described later.

The adjustment operation means 5 prompts the operator to input adjustment values of control parameters to be applied to VCO2, VCA3 and VCF4, and outputs voltage control signals to VCO2, VCA3 and VCF4. The adjustment operating means 5 includes a cutoff frequency adjustment knob 51 , a resonance value adjustment knob 52 , a cutoff frequency adjustment section 53 , a resonance value adjustment section 54 , a resonance adjustment gain change section 55 and an LED light emission section 56 .
Incidentally, in the present embodiment, only the part for adjusting the VCF 4 is described in the adjustment operating means 5. FIG. However, although not shown, the actual adjustment operation means 5 includes a waveform selection knob for the basic waveform of the VCO2 and an adjustment knob for the output sound volume of the VCA3, etc., so that the control parameters to be output to the VCO2 and VCA3 can be adjusted. It is configured.

A cutoff frequency adjustment knob 51 is a knob for adjusting the reference frequency cut off by the VCF 4 . Specifically, the cut-off frequency adjustment knob 51 uses the upper limit frequency when the VCF 4 is LPF (Low Pass Filter), the lower limit frequency when HPF (High Pass Filter), and the center frequency when BPF (Band Pass Filter) as the reference frequency. adjust.
The resonance value adjustment knob 52 changes the resonance value to adjust the degree of enhancement of the band around the cutoff frequency. The resonance value adjustment knob 52 allows the resonance value to be adjusted in multiple steps. Specifically, when the position of the resonance value adjustment knob 52 is 0, the band around the cutoff frequency is not emphasized. As the position of the resonance adjustment knob 52 is raised, the emphasis of the band around the cutoff frequency gradually increases.

A cutoff frequency adjustment unit 53 generates a control parameter based on the cutoff frequency adjusted by the cutoff frequency adjustment knob 51 and gives a control voltage value CV (Control Voltage) to the VCF 4 .
The resonance value adjusting section 54 generates a control parameter based on the resonance value adjusted by the resonance value adjusting knob 52 and gives the control voltage value CV to the VCF 4 .

The resonance adjustment gain changing section 55 changes the gain per unit adjustment amount of the resonance value adjustment knob 52 . That is, the resonance adjustment gain changing unit 55 adjusts the gain of the resonance value when the resonance adjustment knob 52 is changed by one scale, and the gain is set small in the vicinity of the self-oscillation region described later, and the gain is set in the other portions. can be set larger. In this embodiment, the gain change in the resonance adjustment gain changing section 55 is changed based on the control signal from the self-oscillation notification means 9 .

The LED light emitting section 56 is provided near the resonance value adjusting knob 52, and lights up to notify the operator when self-oscillation occurs due to the operation of the resonance value adjusting knob 52. FIG. Lighting control of the LED light emitting section 56 is performed based on a control signal from the self-oscillation notification means 9 . The LED light emitting unit 56 may notify the operator by turning on and off a single-color LED, but may notify the operator by changing the light emission color of the LED so as to change from green light emission to red light emission. may

[2] Self-Oscillation Phenomenon Next, the self-oscillation phenomenon will be described with reference to FIGS. 2 to 4. FIG. 2 to 4, graph (A) is the frequency spectrum of the input/output signal of the VCF 4, graph A1 is the frequency spectrum of the input signal, and graphs A2 to A4 are the frequency spectrum of the output signal. Graph (B) represents temporal changes in the signal level of the input signal, and graph (C) represents the signal level of the output signal corresponding to the time of graph (B).

When the resonance value of the VCF 4 is changed, the VCF 4 outputs an output signal with a frequency different from that of the key identification signal generated by the operator's pressing of the keyboard or the basic waveform generated based on the selected basic waveform. For example, in FIG. 2A, an output signal frequency spectrum graph A2 having a frequency peak P1 that does not exist in the input signal is detected for the input signal frequency spectrum graph A1.
FIG. 2 shows the case where the adjustment amount of the resonance value adjustment knob 52 is small, and the signal level of the peak P1 of the frequency different from the frequency of the original output signal is also small. Therefore, with respect to the basic waveform of the input signal shown in graph (B), the waveform of the output signal shown in graph (C) is almost in sync with the waveform of graph (B) without being affected by the peak P1. state.

FIG. 3 shows a case in which the adjustment amount of the resonance value adjustment knob is increased more than in the case of FIG. there is
However, as can be seen from graph (A), the signal level of peak P2 is approximately the same as the signal level peak of graph A3 of the frequency spectrum of the output signal. Therefore, with respect to the basic waveform of the input signal shown in graph (B), the waveform of the output signal shown in graph (C) has a signal level peak synchronized with the basic waveform of the input signal and a non-synchronous signal level peak. It is detected in a mixed manner with a peak, and becomes a waveform in a state where the self-oscillation phenomenon begins to occur.

On the other hand, FIG. 4 shows the case where the adjustment amount of the resonance value adjustment knob 52 is maximized. You will gain levels. Therefore, in the waveform of the output signal shown in graph (C), a frequency different from the scale of the output signal corresponding to the basic waveform of the input signal is detected, and its period becomes asynchronous with the basic waveform, causing a self-oscillation phenomenon. state.

[3] Structure of Self-Oscillation Determining Means 8 An input signal input to the VCF 4 is obtained by an input signal obtaining means 6 , and an output signal after filtering output from the VCF 4 is obtained by an output signal obtaining means 7 .
The input signal acquisition means 6 detects the signal output from the VCO 2, performs FFT (Fast Fourier Transform) analysis, and generates a frequency spectrum like graph A1 in graphs (A) of FIGS. , a temporal change in signal level as shown in graph (B) is detected, and the result is output to the self-oscillation determining means 8 .

Similarly, the output signal acquisition means 7 detects the signal output from the VCF 4, performs FFT analysis, and generates frequency spectra such as graphs A2 to A4 in graphs (A) in FIGS. , a temporal change in the signal level as shown in graph (C) is detected, and the result is output to the self-oscillation determining means 8 .

The self-oscillation determination means 8 is based on the frequency component of the input signal input to the VCF 4 acquired by the input signal acquisition means 6 and the frequency component of the output signal output from the VCF 4 acquired by the output signal acquisition means 7. , and VCF 4 are self-oscillating.
The self-oscillation determining means 8 includes a sampling clock generating section 81, an output signal sampling section 82, a sampling result holding section 83, a synchronization state detecting section 84, and an oscillation determining section 85, as shown in FIG.

The sampling clock generator 81 generates a sampling clock SC for sampling the output signal based on the basic waveform of the input signal. Specifically, as shown in FIG. 6, the sampling clock generation unit 81 detects the time of the zero cross point of the input signal in the temporal change of the input signal shown in graph (B), A sampling clock SC with a period T2 is generated. In this embodiment, the sampling clock SC is generated based on the zero cross point, but the sampling clock SC may be generated by detecting the time when the input signal takes the maximum value.

The output signal sampling section 82 samples the signal level of the output signal output from the VCF 4 based on the sampling clock SC generated by the sampling clock generation section 81 . Specifically, as shown in FIG. 7, the output signal sampling unit 82 samples the signal level from the output signal of the graph (C) output from the VCF 4 at the sampling period T1 and the sampling period T2. A sampling result is output to the sampling result holding unit 83 .
The sampling result holding unit 83 accumulates and holds the sampling results sampled by the output signal sampling unit 82 for a predetermined period. The retained sampling results are averaged and output to the synchronization state detector 84 .

A synchronous state detection unit 84 detects whether the output signal output from the VCF 4 is in a synchronous state or asynchronous state with the input signal based on the sampling result held by the sampling result holding unit 83 . Specifically, the synchronization state detection unit 84 detects that the signal levels of the input signal and the output signal obtained by the input signal obtaining means 6 and the output signal obtaining means 7 are equal to or higher than a predetermined threshold. A synchronized state is detected when any of the following cases apply.

[Synchronous state detection conditions]
(1) The sampling clock SC is generated from the input signal to VCF4.
(2) The signal level of the sampling result is constant with no change. That is, the signal level of the sampled output signal should match at each sample, and the input and output signals should be perfectly synchronized.
(3) Changes are observed in the signal level of the sampling results, but they are periodic changes. In other words, the frequency of the output signal is the second overtone and the third overtone with respect to the scale based on the frequency of the input signal.

However, the above detection condition requires that the input to the VCF 4 is a waveform composed only of harmonically related components. For example, the output from VCO2 corresponds to a single sawtooth wave or triangular wave.
When there are two or more inputs from the VCO 2, the detection condition can be satisfied if the respective inputs are synchronized by the SYNC function or the like.
It is also necessary that the point from which the input signal is extracted should be purely the output of VCO2. This is because the input signal must be extracted from a portion of the VCF 4 that is not affected by feedback for resonance.
The synchronization state detection section 84 outputs the detection result to the oscillation determination section 85 .

The oscillation determining section 85 determines whether or not self-oscillation is occurring based on the synchronous or asynchronous state of the sampling result detected by the synchronous state detecting section 84 . Specifically, the oscillation determination unit 85 determines that the self-oscillation phenomenon occurs when all of the following conditions are met.
[Self-oscillation criteria]
(1) When the synchronous state detection unit 84 detects that it is asynchronous.
(2) when the signal level of the input signal acquired by the input signal acquisition means 6 is equal to or higher than a predetermined threshold;
The oscillation determination section 85 outputs the determination result to the self-oscillation notification means 9 .

The self-oscillation notification means 9 outputs a control signal for changing the adjustment gain to the resonance adjustment gain changing section 55 and a lighting/lighting control signal to the LED light emitting section 56 based on the determination result of the oscillation determination section 85 . Specifically, when the oscillation determination unit 85 determines that the self-oscillation phenomenon is occurring, the self-oscillation notification unit 9 outputs a control signal for changing the adjustment gain to the resonance adjustment gain change unit 55, and the LED A control signal is output to cause the light-emitting portion 56 to turn on in a lighting state when the self-oscillation phenomenon occurs. If it is determined that the self-oscillation phenomenon has not occurred, no control signal is output to the resonance adjustment gain changer 55 and a control signal for maintaining the current lighting state is output to the LED light emitter 56 .

The resonance adjustment gain changer 55 adjusts the gain of the resonance value adjustment knob 52 based on the control signal from the self-oscillation notification means 9 . Specifically, when the oscillation determination unit 85 determines that the self-oscillation phenomenon is occurring, the resonance adjustment gain change unit 55 reduces the gain per unit adjustment amount of the resonance value adjustment knob 52 to finely adjust the resonance. Allows adjustment of values. If it is determined that the self-oscillation phenomenon has not occurred, the resonance adjustment gain changing section 55 does not perform gain adjustment.

[4] Actions of the Embodiment Next, actions of the present embodiment will be described with reference to the flowchart shown in FIG.
When an operator operates a UI such as a keyboard, a key identification signal giving a keyed scale is input to the VCO 2 (step S1). The VCO 2 generates an input signal having a preselected basic waveform based on the key identification signal (step S2).
The input signal generated by the VCO 2 is input to the VCF 4, which adjusts the basic waveform of the input signal based on the cutoff frequency adjusted by the cutoff frequency adjustment knob 51 and the resonance value adjusted by the resonance adjustment knob 52. Processing is performed (step S3).

The input signal acquisition means 6 acquires the input signal input to the VCF 4 generated by the VCO 2, performs FFT analysis and the like, and outputs the signal to the self-oscillation determination means 8 (step S4).
The output signal acquiring means 7 acquires the output signal output from the VCF 4, performs FFT analysis and the like, and outputs it to the self-oscillation determining means 8 (step S5).

The sampling clock generator 81 generates the sampling clock SC based on the input signal obtained by the input signal obtaining means 6 (step S6).
The output signal sampling unit 82 samples the signal level of the output signal based on the generated sampling clock SC (step S7).

The synchronous state detector 84 detects whether or not the input signal and the output signal are in a synchronous state based on the signal level of the sampled output signal (step S8). The synchronization state detection unit 84 determines whether or not any of the synchronization state detection conditions described above is met.
Synchronization state detection section 84 determines that the input signal and the output signal are in a synchronization state when either of the two synchronization conditions is met, and outputs the detection result to that effect to oscillation determination section 85 .

The oscillation determination unit 85 determines self-oscillation according to self-oscillation determination conditions based on the detection result input from the synchronization state detection unit 84, the resonance value set by the resonance value adjustment knob 52, and the signal level of the input signal. A determination is made (step S9).
If any of the self-oscillation determination conditions are not satisfied, the oscillation determination unit 85 concludes that the self-oscillation phenomenon has not occurred and terminates the process.
When it is determined that all the self-oscillation determination conditions are satisfied, the oscillation determination section 85 outputs a determination result to the effect that self-oscillation is occurring to the self-oscillation notification means 9 .
The self-oscillation notification means 9 outputs a control signal to the resonance adjustment gain changing section 55 based on the determination result that the self-oscillation phenomenon has occurred, and also outputs a control signal to the LED light emitting section 56 when the self-oscillation phenomenon has occurred. A control signal for turning on the lighting state is output to inform the operator that the self-oscillation phenomenon is occurring (step S10).

[5] Effects of the Embodiment According to the present embodiment, the following effects are obtained.
The analog synthesizer 1 includes self-oscillation determination means 8 and self-oscillation notification means 9 . Therefore, depending on the adjustment state of the cutoff frequency adjustment knob 51 and the resonance value adjustment knob 52, it is determined whether or not self-oscillation occurs in the VCF 4, and the operator is made to recognize it by causing the LED light emission part 56 to emit light, and the analog It is possible to prevent the synthesizer 1 from generating dissonance.

The self-oscillation determination means 8 includes a sampling clock generation section 81 and an output signal sampling section 82 . Therefore, the sampling clock SC can be immediately generated from the input signal, and the signal level of the output signal corresponding to the sampling clock SC can be detected to easily detect the synchronous state of the input signal and the output signal.

The oscillation determination unit 85 is operated based on the detection result of the synchronization state of the synchronization state detection unit 84, the resonance value obtained by the resonance value adjustment knob 52 being equal to or higher than a predetermined threshold value, and the signal level of the input signal being equal to or higher than a predetermined threshold value. , to determine whether or not the self-oscillation phenomenon has occurred. Therefore, it is determined that the self-oscillation phenomenon has occurred only when the output acoustic signal has a volume equal to or higher than a predetermined volume and the resonance value at the cutoff frequency is equal to or higher than a predetermined threshold. Therefore, since the occurrence or non-occurrence of the self-oscillation phenomenon is determined under limited conditions, the operator can recognize the self-oscillation phenomenon under the limited conditions, and the limitation of sound creation by the analog synthesizer 1 can be prevented. can be kept to a minimum.

The determination result of whether or not the self-oscillation phenomenon has occurred by the oscillation determining section 85 is output to the resonance adjustment gain changing section 55 via the self-oscillation reporting means 9 . Then, when the self-oscillation phenomenon occurs, the resonance adjustment gain changing section 55 reduces the adjustment gain per operation amount of the resonance value adjustment knob 52 . Therefore, when it is determined that the self-oscillation phenomenon is occurring in the VCF 4, by reducing the gain per operation amount, it becomes possible to finely adjust the resonance value, and the operability of the resonance value adjustment is improved.

[6] Second Embodiment Next, a second embodiment of the present invention will be described. In the following description, the description of the same parts as those already described will be omitted.
In the above-described first embodiment, the synchronous state detector 84 determines whether the signal levels of the detected input signal and output signal match completely or, even if a change is recognized, is a periodic change. , is determined to be synchronized. The oscillation determination unit 85 determines that the synchronous state detection unit 84 is asynchronous, the adjustment amount of the resonance value is equal to or greater than a predetermined threshold value, and the input signal is at a predetermined level, self-oscillation occurs. was determined to be

On the other hand, in the present embodiment, as shown in FIG. 9, a sound generated by combining the resonance value (RES) and the cutoff frequency (FREQ) in advance is output, and the listener is allowed to listen to the sound. The difference is that the listener is made to judge whether or not oscillation is occurring, the judgment result is stored, and whether or not self-oscillation is occurring is judged from the stored judgment result.
Specifically, the self-oscillation determining means sets the number of resonance value patterns before the analog synthesizer plays (step S11), and then sets the number of cutoff frequency patterns (step S12).

Next, the self-oscillation determining means sets the resonance value and the cutoff frequency to the initial values of the set pattern (step S13).
Based on the set values, the UI such as the keyboard is pressed to output sound based on the set resonance value and cutoff frequency (step S14).
The listener is made to listen to the output sound, determine whether or not self-oscillation is occurring, and is prompted to input the determination result (step S15). Note that the determination result can be obtained by prompting the user to operate a predetermined button on the analog synthesizer.

When the determination result that self-oscillation occurs is input, the self-oscillation determination means writes in a storage device such as a memory that self-oscillation occurs with the set combination of the resonance value and the cutoff frequency (step S16). .
When the determination result that self-oscillation does not occur is input, the self-oscillation determination means writes in a storage device such as a memory that self-oscillation does not occur with the combination of the set resonance value and cutoff frequency (step S17). ).

The self-oscillation determining means determines whether or not determination has been completed for all combinations of resonance values and cutoff frequencies (step S18).
If determination has been completed for all combinations, the self-oscillation determining means terminates the processing.
If determination has not been completed for all combinations, the self-transmitting determination means updates either the resonance value or the cutoff frequency to a new setting (step S19), and repeats steps from step S14.

After the above pre-performance preparations are completed, the operator is notified of the determination result of self-oscillation based on the flow chart shown in FIG. 10 during the performance by the operator.
First, the self-oscillation determination means obtains the resonance value set by the operator by operating the resonance value adjusting knob (step S20).
The self-transmission determining means acquires the cutoff frequency set by the operator by operating the cutoff frequency adjusting knob (step S21).

The self-oscillation determining means determines whether or not self-oscillation occurs based on the combination of the resonance value and the cutoff frequency set by the operator (step S22). The determination is made based on the determination result stored in a storage device such as a memory in preparation before the performance, based on whether or not the value set by the operator self-oscillates.
If it is determined that self-oscillation does not occur, the process proceeds to the next step S24 without displaying the self-oscillation state.
If it is determined that self-oscillation occurs, the self-oscillation notification means displays that it is in the self-oscillation state (step S23).

The self-oscillation determining means prompts the operator whether or not it is necessary to change the set value of the resonance value or the cutoff frequency (step S24).
When the operator determines that the set value needs to be changed, the self-oscillation determining means prompts the operator to operate the resonance adjustment knob or the cutoff frequency adjustment knob to change the resonance value or the cutoff frequency (step S25). Repeat from S20.
If it is determined that the setting value does not need to be changed, a voice is output by keying on the UI (step S26).

In the present embodiment, self-oscillation is determined based on a combination of cutoff frequency and resonance value patterns, but the present invention is not limited to this. Parameters related to self-oscillation include cutoff frequency, resonance value, envelope amount, sustain, etc., so self-oscillation may be determined using a quaternary array matrix combining these parameters.

According to this embodiment, the same effects as those described above can be obtained.
In addition, since the listener judges the self-oscillation state by listening, the judgment standard can be set in a state close to human hearing, and the self-oscillation state can be judged with higher accuracy.
Furthermore, since it is possible to inform the operator whether or not the self-oscillation state occurs before voice output by keying on the UI, it is possible to reliably prevent the listener from hearing dissonance caused by the self-oscillation phenomenon.

[7] Modifications of the Embodiments The present invention is not limited to the above-described embodiments, but includes the following modifications.
Although the analog synthesizer 1 has been described in the above embodiment, the present invention is not limited to this. For example, the present invention may be applied to audio equipment such as DJ mixers and samplers equipped with VCFs similar to those of the above-described embodiments. The present invention may also be applied to measures against oscillation in audio amplifiers and measures against self-oscillation in high-frequency transmitters.

In the above-described embodiment, the signal level of the output signal is sampled by the sampling clock SC generated from the input signal to detect the synchronous state, but the present invention is not limited to this.
That is, the control voltage value CV of the cutoff frequency of the VCF and the control voltage value CV of the resonance value are measured in advance, and the point at which the self-oscillation phenomenon occurs is grasped in advance and stored in a storage device such as a memory. During operation, these control voltage values CV may be detected in real time and compared with the control voltage values at which the self-oscillation phenomenon occurs in the storage device to determine self-oscillation. However, in this case, errors caused by temperature changes cannot be dealt with.

In the above-described embodiment, whether or not the self-oscillation phenomenon occurs is determined based on the input signal and output signal of one VCF 4 used in the analog synthesizer 1, but the present invention is not limited to this. .
That is, another VCF is prepared in parallel with VCF4, and the same input signal is input to the two VCFs from VCO2. The other VCF is set to have the same cutoff frequency as VCF4, but the resonance value is set to a value around 0.65 that does not cause the self-oscillation phenomenon. Then, the signal levels of the output signals output from the two VCFs are detected, and if the signal level of the output signal of the VCF becomes significantly larger than that of another VCF connected in parallel (if it exceeds a predetermined threshold value) , it may be determined that the self-oscillation phenomenon has occurred.

In the above-described embodiment, when it is determined that the self-oscillation phenomenon has occurred, the operator is notified of the occurrence of the self-oscillation phenomenon by turning on the LED light emitting unit 56. However, the present invention is limited to this. can't For example, the operator may be made aware of the occurrence of the self-oscillation phenomenon by an acoustic signal or by vibrating the resonance value adjustment knob 52 .
In addition, the specific structure, shape, and the like in carrying out the present invention may be other structures and the like as long as the object of the present invention can be achieved.

DESCRIPTION OF SYMBOLS 1...Analog synthesizer 2...VCO 3...VCA 4...VCF 5...Adjustment operation means 6...Input signal acquisition means 7...Output signal acquisition means 8...Self-oscillation determination means 9...Self-oscillation notification means , 53... Cut-off frequency adjusting section, 54... Resonance value adjusting section, 55... Resonance adjusting gain changing section, 56... LED light emitting section, 81... Sampling clock generating section, 82... Output signal sampling section, 83... Sampling result holding section , 84 . Sampling clock, T1... Sampling period, T2... Sampling period.

Claims (6)

a filter processing means for performing filter processing for processing the waveform of an input signal and outputting the waveform;
adjustment operation means for allowing an operator to adjust control parameters for filtering by the filtering means;
an input signal obtaining means for obtaining an input signal to the filtering means;
an output signal obtaining means for obtaining an output signal filtered by the filtering means;
Self-oscillation determination for determining whether or not self-oscillation occurs based on the synchronization state of the input signal and the output signal by comparing the acquired frequency component of the input signal and the acquired frequency component of the output signal. means and
self-oscillation notification means for notifying the operator of the occurrence of self-oscillation when the self-oscillation determination means determines that self-oscillation is occurring;
Acoustic equipment with In the acoustic device according to claim 1,
The self-oscillation notifying means is an acoustic device that visually recognizes the operator. In the acoustic equipment according to claim 1 and claim 2,
The self-oscillation determination means is
a sampling clock generator that generates a sampling clock from the obtained waveform of the input signal;
an output signal sampling unit for sampling the signal level of the acquired output signal by the sampling clock generated by the sampling clock generation unit;
a synchronization state detection unit for detecting a synchronization state based on the signal level of the input signal according to the sampling clock generated by the sampling clock generation unit and the signal level of the output signal sampled by the output signal sampling;
an oscillation determination unit that determines whether or not self-oscillation occurs based on the synchronization state detected by the synchronization state detection unit;
Acoustic equipment with In the acoustic device according to claim 3,
The oscillation determining section detects when the periods of the signal level of the input signal and the signal level of the output signal detected by the synchronization state detecting section are the same, or when the periods are different but are synchronized in a predetermined period. Also, an acoustic device that determines that self-oscillation does not occur. In the acoustic equipment according to claim 3 or claim 4,
The oscillation determination unit determines that the synchronization state detected by the synchronization state detection unit is asynchronous, and self-oscillation occurs when the signal level of the input signal input to the filtering unit is equal to or higher than a predetermined threshold. audio equipment that determines that A computer-readable self-oscillation determination program that causes a computer to function as the acoustic device according to any one of claims 1 to 5.

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