JPH0370234B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tuner applied to tuning a sounding body such as a guitar string, and more particularly to a tuner that can stabilize the tuning display state of the sounding body on a display.

Musical instruments must be tuned accurately, and this tuning has a great effect on the sound of the performance, especially when played in ensemble with other instruments. Therefore, performers pay sufficient attention to the tuning of their instruments, and professional tuners are in charge of tuning work during important performances. For example, when tuning a guitar, listen to the sound produced by a tuning fork that generates a vibration sound of 4A = 440Hz, and use this as a reference to tune the strings of 5A = 110Hz. Next, based on this 5A string note, the other strings are tuned while performing operations such as generating notes of other scales while performing fret operations.

However, this tuning requires adjustment with an accuracy of a frequency difference of 1/50 to 1/100 of a semitone, but it is generally extremely difficult to discern the range of such minute frequency differences.

To solve this problem, a tuner is used that electronically measures the frequency difference between the reference frequency and the generated sound, and displays the amount of deviation between the two on a meter.

FIG. 1 is a circuit diagram showing an example of a tuner commonly used in the past, and specifically shows a tuner for guitars. This tuner is configured such that a musical tone signal converted by an acoustoelectric transducer such as a microphone (not shown) is supplied to an input end 1, and the musical tone signal supplied to this input end 1 is The signal is amplified in an amplifier 2 as shown in FIG. 2a and then supplied to a synchronous oscillator 3 as a fundamental wave signal sending circuit. The synchronous oscillator 3 is provided to extract the fundamental wave component contained in the musical tone signal, and by oscillating in synchronization with the fundamental wave component, it generates a rectangular wave signal with the fundamental wave period shown in FIG. 2b. Send out. In this case, the synchronous oscillator 3 needs to oscillate in synchronization with the musical tone signals generated by each string, but this results in an extremely wide frequency range for all strings, resulting in loss of synchronization. For this purpose, the synchronous oscillator 3 is connected to the terminal by the switch 4a.
By selectively connecting a resistor for setting the free-running frequency between _K1 and _K2 , the free-running frequency is switched in accordance with the tuning string to prevent synchronization.

In this way, the rectangular wave signal of the fundamental wave period of the musical tone signal shown in FIG. 2b, which is sent out from the synchronous oscillator 3, has its rising part differentiated in the differentiating circuit 5, and the rectangular wave signal shown in FIG. A narrow differential pulse train synchronized with the rising edge of the pulse is supplied to the one-shot circuit 6. The one-shot circuit 6 is triggered by the differential pulse supplied from the differentiating circuit 5, and has a width corresponding to the value of the time constant determining resistors 6a to 6f selected by the switch 4b and is synchronized with the differential pulse. The pulse shown in FIG. 2d is sent out. Therefore, from the one-shot circuit 6, the selection resistors 6a to 6 are selected by the switch 4b, as shown in FIG.
A pulse having a pulse width T ₁ corresponding to f and a period T ₂ of the fundamental wave component of the input musical tone signal is transmitted. The output pulse of the one-shot circuit 6 generated in this manner is smoothed in an integrating circuit 7 and then supplied to an indicator 8, where its voltage value V is indicated. Then, the output value V of the integrating circuit 7 in this case is V=K・T ₁ /T ₂ =K・T ₁・f ₀ (1), and the frequency f ₀ of the fundamental wave component of the musical tone signal A voltage proportional to will appear. Since this frequency f ₀ is divided into multiple types of tuning frequencies depending on each string of a guitar, for example, in order to display the tuning state of each string using the same indicator 8, it is necessary to use the above equation (1). The proportionality constant must be adjusted by switching the pulse width T ₁ depending on the string so that the zero position is the same. The relationship between the frequency f ₀ and the pulse width T ₁ is as follows: f′ ₀ ·T′ ₁ =f ₀ ·T ₁ (2), and they are inversely proportional to each other. To switch this pulse width _T1 , in conjunction with the switch 4a that selects the free-running frequency setting resistors 3a-3f corresponding to the tuning string, the time constant determining resistors 6a-66
This is done by switching the switch 4b which selects f.

Therefore, in the tuner constructed in this way, a musical tone is generated by switching the switches 4a, 4b corresponding to the tuned string and then plucking the tuned string. Then, the instruction state of the indicator 8 with respect to the musical tone generated from the tuned string is confirmed, and tuning is performed so that the instruction becomes a zero instruction and the error becomes zero, thereby completing the tuning.

However, the tuner with the above configuration is configured so that a common indicator and indicating point can be used for each string by switching the constant KT ₁ with respect to the output voltage for driving the indicator. Since the constant is adjusted by switching the time constant of the one-shot circuit, it is extremely difficult to adjust, and it fluctuates greatly as the temperature changes. On the other hand, the basic unit of music is a semitone, which corresponds to a frequency difference of about 6%, but human hearing generally has the ability to distinguish between 1/50th and 1/100th of a semitone. Therefore, tuning using the above-mentioned tuning device has low accuracy and is unstable, so it is not practical.

The purpose of this invention is to eliminate the above-mentioned drawbacks of the conventional instruments, make it possible to measure frequency differences of 1/50 to 1/100 of a semitone with high accuracy, eliminate instability such as resistance fluctuations, and It is an object of the present invention to provide this type of tuner that is highly practical by minimizing the influence of frequency fluctuations and making it easy to use.

Hereinafter, one embodiment of the tuner according to the present invention will be described in detail with reference to FIG. 3 and subsequent figures.

FIG. 3 is a circuit diagram showing an embodiment of the tuner according to the present invention, and the same parts as in FIG. 1 are shown using the same symbols. In the figure, 10 is amplifier 2
A synchronous oscillator serving as a fundamental wave signal sending circuit that sends out a rectangular wave signal with a fundamental wave period synchronized with a fundamental wave signal included in a musical tone signal supplied from the synchronous oscillator, which is configured as shown in FIG. 4, for example. . That is, this synchronous oscillator 10 has open collector type comparators A ₁ and A ₂ , and comparator A ₁ has a resistor R ₁ between its output terminal and inverting input terminal, and also has an inverting input terminal. A capacitor for charging and discharging is connected between the end and ground.
C ₁ is connected. Furthermore, the musical tone signal from the amplifier 2 is supplied to the non-inverting input terminal of the comparator _A1 via the coupling capacitor _C2 , and the reference voltage obtained by dividing the power supply Vcc by the resistors _R2 and _R3 is supplied. Voltage is applied. In addition, a resistor R4 is connected between the output terminal of the comparator _A1 and the power supply +Vcc, which acts as a load resistor and also serves as a charging resistor for the capacitor _C1 when the output of the comparator _A1 is at the "H _" level. has been done.

On the other hand, the comparator A ₂ uses the output of the comparator A ₁ as a non-inverting input, and a reference voltage obtained by dividing the power supply Vcc by resistors R ₅ and R ₆ is applied to the inverting input. Further, the comparator _A2 stabilizes its operation by feeding back its output to the non-inverting input of the comparator _A1 via the resistor _R7 .

In the synchronous oscillator 10 configured as described above, the output of the comparator _A1 is normally at the "H" level, and when the comparator _A1 becomes "H", the output is connected to the capacitor via the resistors _R4 and _R1 . C ₁ is charged in response to a time constant determined by C ₁ (R ₁ +R ₂ ). Then, when the charging voltage of this capacitor C ₁ rises above the reference voltage obtained by dividing the power supply Vcc by resistors R ₂ and R ₃ ,
The output of comparator _A1 is inverted to "L" level.
Then, when the output of comparator _A1 becomes "L" level, the electric charge stored in capacitor _C1 is transferred to the resistance
It is discharged through R ₁ and one cycle of operation is completed, and the output change of comparator A ₁ is waveform-shaped in comparator A ₂ and then sent out from the output terminal OUT, and this rectangular The wave output is synchronized with the fundamental wave signal included in the musical tone signal supplied via the coupling capacitor _C2 .

In this case, the charging time constant is determined by the resistors R ₁ and R ₄ and the capacitor C ₁ , and the masking time is set accordingly.

Therefore, by setting the value of the resistor _R4 in accordance with the tuning string, a free running frequency corresponding to the frequency of the input musical tone signal is set. In the circuit shown in FIG. 3, the free-running frequency setting circuit 11 corresponding to the resistor _R4 is configured by a ladder connection of resistors 11a to 11f having different values, and the resistors 11a to 11f are selected. The free running frequency (masking time) is adjusted by doing this. 12 is a tuning string specifying circuit, 1E, 2
It is composed of string designation switches 12a to 12f, each of which designates the strings B, 3G, 4D, 5A, and 6E, and one end of which is commonly connected to the power supply +Vcc.
Reference numeral 13 is a central processing unit (hereinafter referred to as CPU) that performs various calculations and control processing, and is a central processing unit (hereinafter referred to as CPU) that performs various calculations and control processing, and is connected to each string designation switch 12a to 12 of the tuning string designation circuit 12.
The string designation signal output from f is input to ports i ₈ to _{i 13.}
and outputs the calculation output to ports i ₈ to _{i 13.}
The calculation output is sent from the output port _Os to the indicator 8 having an LCD structure, and the output of the synchronous oscillator 10 is also taken in via the interrupt input terminal INTO. 14 is an oscillator having a crystal oscillator 15; 16 is a binary counter which receives the output pulse of the oscillator 14 as a clock input; its parallel outputs _Q1 to _Q8 are supplied to input ports _i0 to _i7 of the CPU 13; ing. Further, this counter 16 has a configuration in which data can be read out in parallel, and is reset-controlled by the output port _Os of the CPU 13, and the most significant bit output _Q8 is sent to the CPU 1 via an inverter 17a and a NAND gate 18.
3 interrupt input port 1. Note that the other input terminal of the NAND gate 18 is
A signal sent from the output port _O7 of the CPU 13 is supplied via the inverter 17b. 19 connects the most significant bit output of the counter 16 to the inverter 17
a as a clock input, and inverter 1
It is a flip-flop which uses the output of 7b as a reset input, and its set output Q is supplied to the input port _i14 of the CPU 13. And above
For example, as shown in FIG. 5, the CPU 13 includes a ROM,
It has a generally well-known configuration including RAM, ALU, program counter, instruction decoder, input/output ports, interrupt input, etc. In this case, an LCD driver with an LCD configuration is built-in, but it may be provided externally.

In the tuner configured as described above, when the string designation switches 12a to 12f of the tuning string designation circuit 12 are selectively operated in accordance with the string to be tuned,
A string designation signal is supplied to the CPU 13 from the operated string designation switches 12a to 12f. CPU1
3 calculates the reference frequency for the target string by taking in this string designation signal, and selects the corresponding output port O ₁ to O ₆ to generate an oscillator synchronized with the fundamental wave component included in the musical tone signal of that band. Resistors 11a to 11f of the free-running frequency setting circuit 11 necessary for making the free-running frequency setting circuit 10 run freely are selected.
In this state, when a musical tone signal emitted from the tuned string is supplied to the input terminal 1, this musical tone signal is amplified by the amplifier 2 and then sent to the synchronous oscillation circuit 10.
supplied to As described above, the synchronous oscillation circuit 10 sequentially generates the rectangular wave signal shown in FIG.
13 interrupt input port INT0. CPU1
3 is the interrupt input port INT0 from the synchronous oscillator 10
During one period of the square wave signal supplied to the oscillator 14
The difference between the frequency of the fundamental wave component of the musical tone signal and the reference frequency for the string designated by the string designation switches 12a to 12f is calculated by counting the number of clock pulses output from the clock pulses and calculating the time. The indicator 8 is giving instructions. In this embodiment, as also shown in FIG. 6a, the period T/6 is calculated by measuring the time T for n periods of the rectangular wave signal. In this case, the time is measured by counting the output pulses of the oscillator 14 supplied to the counter 16 during the time period T, but the time is measured by 1/50 to 1/100 of a semitone (approximately 0.06%). ), it is necessary to count a large number of high-frequency pulses, and if counting is performed in this state, a counter with an enormous number of digits will be required. Therefore, in this case, only a counter having the minimum necessary number of bits is provided inside the CPU 13, and the carry signal of the external counter 16 is used.
CPU13 by interrupting CPU13.
This number of interrupts is stored in its internal RAM. That is, from the output port _O8 of the CPU 13 to FIG.
A reset pulse shown in is sent to the counter 16.
During the period T from when the counter 16 is reset to when the predetermined number n of square wave signals shown in FIG. 6a is counted, the output terminal _Q8 of the counter 16 is
The number of falling edges of the signal shown in FIG. 6c sent from the controller is stored. Therefore, Fig. 6 a, c
The square wave signal shown in and the output terminal of the counter 16
In response to the output of _Q8 , the CPU 13 outputs the interrupt input ports INT0 and INT0 at the timing shown in Figure 6d and e.
Process the INT1 signal as an interrupt. When the number of interrupts to the interrupt input port INT0 reaches a predetermined number n times by the output of the synchronous oscillator 10, the CPU 13 reads the remaining count x of the counter 16 and performs the calculation shown in the following equation. The time T is calculated accordingly.

T=n・t+x+y ₁ −y ₂ ...(3) However, t is the sixth output from counter _Q8 .
The period of the pulse shown in Figure c, _y1 is the delay time from the start of the interrupt until the counter 16 is reset.
_y2 is the delay time from the start of the interrupt until reading the remainder of the counter value, and both are constants.

In this way, when measurements are performed using two types of interrupt processing, these interrupt inputs may overlap each other because they are input asynchronously. In general, a CPU can handle multiple interrupts, but if the processing starts with a signal from the interrupt input port, for example,
Configured by RAM inside the CPU13
At the very least, the count up for the INT1 counter must be executed. Therefore, during this period, the interrupt processing for INT0 cannot be performed, and as a result, the processing for INT0 is made to wait, as shown by the dot in FIG. 6d. If this overlap occurs at the timing when the value of the counter 16 is finally read, the value x of the counter 16 will not be read accurately, and as a result, the above-mentioned accuracy of 0.06% cannot be obtained. I end up. Therefore, in this embodiment, as shown in FIG. 6f, the CPU 1
By outputting a masking signal for interrupt 1 from the output port O ₇ of the CPU 13 a little before the final interrupt INT0 is input from the output port O ₇ of the CPU 13, the NAND gate 18 is closed and the next input interrupt 1 is output. Prohibits one dose. The start timing of this masking is determined by the accuracy guaranteed range of the indicator 8, and starts from the time when interrupt signal 1 arrives, just before the time when interrupt signal INT0 arrives at the highest frequency within the guaranteed range. . In this case, the human ear is 0.06%
Since it is possible to distinguish between sounds with an accuracy of 0.06%, the frequency measurement accuracy of the tuner must also be 0.06%.
On the other hand, since the value displayed on the indicator 8 is read visually by the tuner, it is sufficient to ensure an accuracy of about ±0.5.
Therefore, the interrupt timing of INT0 mentioned above is
If the point where the INT1 interrupt timing overlaps is in the middle of the predetermined number of INT0 interrupts, the error due to overlap delay is ±0.5
There is no problem as long as the display accuracy is within the range of about 100%.
However, if the overlap occurs when the scheduled number of interrupts for INT0 is reached, the accuracy of the tuner cannot be guaranteed.

Therefore, as shown in Fig. 6e, the interrupt signal 1 (period measurement pulse) synchronized with the falling edge of the output _Q8 of the most significant bit of the counter 16 (see Fig. 6C) is applied once before and after the scheduled number of times. One by one (total of 2 cycles)
If you measure with interrupts disabled, the problem of overlap will disappear. Instead, if the period measurement pulse time x during the period in which interrupts are prohibited is determined and corrected, an accuracy of 0.06% can be guaranteed, and the accuracy of the indicator can also be guaranteed.

Figures 7 to 9 are enlarged time charts showing before and after the scheduled number of interrupts INT0 is input, and each shows three cases of f > f ₀ , ff ₀ , and f < f ₀ . There is. However, f is the measurement frequency, f ₀
is the fundamental frequency of the string.

First, FIGS. 7a to 7c are cases where f>f ₀ , and before masking of interrupt 1 starts at the timing shown in FIG. is input. Then, the value counted by the counter 16 during a period corresponding to time x is taken into the CPU 13. 8a to 8c show the case where f≈f ₀ , and the final interrupt INT0 is input during masking for interrupt 1 after entering the guaranteed accuracy range.

Further, FIGS. 9A to 9D show the case where f< _f0 , and the final interrupt INT0 is input after the masking period for the interrupt INT1 ends. In this way, when the final interrupt INT0 is input after the end of the masking period of 1, the number of interrupts of 1 is always reduced by one. Therefore, in this case, by setting the C flag in the memory of the CPU 13 as shown in FIG. 9(d) at the same time as masking is completed, it is possible to make corrections by looking at this C flag.

As is clear from FIG. 9d, the masking period t _M
must be in the range t<t _M <2t. Therefore, the setting of the masking period t _M is such that after the masking start interrupt 1 arrives and the predetermined processing is completed, the interrupt is
This is achieved by configuring a loop in software that waits for a certain period of time with INT0 enabled and interrupt 1 disabled.

Furthermore, as a special case, as shown in Figures 10a to 10d, an interrupt is generated during the masking period and after a request 1 for which interrupts are disabled is received.
This is the case when INT0 is input. In this case,
Even though the C flag is "0" as described above, the accurate frequency f cannot be determined unless the interrupt request portion marked with an "X" is added to the count value. For this purpose, flip-flop 19 in FIG. 3 is utilized. That is, when a request for interrupt 1 occurs during the masking period, the flip-flop 19 changes its set output Q from "L" to "H".
invert it. Therefore, in the above case, by reading the set output Q of the flip-flop 19 from the input port _i14 of the CPU 13, the interrupt INT1
It can be seen that the request existed before the final interrupt INT0.

In this way, when the final interrupt INT0 is input and processed, the value of the external counter 16 is changed to the CPU 1.
3, and arithmetic processing for display begins. Then, during this period, the next interrupt
A mask signal is sent to prohibit all requests for interrupt 1 until INT0 arrives.

If we represent this kind of operation in a flowchart,
As shown in FIGS. 11 to 13.

FIG. 11 shows the flow of the main routine. It starts with a reset operation such as turning on the power, initializes in step S1, and then outputs interrupt signals while monitoring each switch input in step S3.
Wait for INT0, 1. And step S4
When a switch input is detected in , the constant f′ ₀ ,
m, n ₀ are set in step S6, and according to this process, the synchronous oscillator 10 and the charge up resistor 11 are
A to 11f are selected in step S7. The constant to be set is: m: Number of SIG pulses during measurement period T f′ ₀ = f ₀ /m: Center frequency of selected string/SIG
The number of pulses n ₀ is the number of interrupts of 1 to start masking of 1, and the period T is approximately constant in order to keep the accuracy constant for each string. Since m changes approximately in proportion to the string frequency, the center frequency of the string is
Rather than using f ₀ as is, setting it as f ₀ /m makes it easier to reduce the dynamic range of data and ensure calculation accuracy. Here,
The S-FLAG in steps S2 and S8 indicates that the next interrupt INT0 is the start of the measurement period T, and the interrupt disabling and interrupt enabling in steps S5 and S9 are performed by interrupt control executed on software. In some cases, INT0 and INT1 interrupts are disabled or enabled at the same time.

FIG. 12 is a flowchart showing the processing contents of step 1. In step S11, n is a number counter of 1 and corresponds to the upper bit of the external counter 16, and the process in step S15 is a waiting loop until the masking period reaches _tM . In other words, the content of this flow is that when 1 request is accepted, the number counter is incremented in step S11.
1, it is checked in step S13 whether or not it is equal to the set value _n0 , and if it is not equal, the process returns, and if it is equal, the mask signal is set to "H" in step S14, and the masking period wait loop step S15 is performed. If there is no request for INT0 until the masking period elapses, step S
At step 16, the mask signal is returned to "L" and C-FLAG is set to "1".

FIG. 13 is a flowchart showing the processing contents of INT0. When the process starts, first step S21
Then, it is checked whether the interrupt signal INT0 is the first INT0 of measurement, and if it is the first INT0, the process executes the measurement start process shown in steps S22, S23, and S24, and then returns. Then, for subsequent INT0, step S2
After incrementing the pulse counter by 1 in step S27, it is checked whether it is equal to the set value m,
Return until they are equal. When the count value of the pulse counter reaches the set value m, the value x of the external counter 16 is read in step S28.
In order to know at what timing INT0 entered, first check C-FLAG in step S29, and if this C-FLAG is set to "1", then 1 will definitely be missed once. Therefore, in step S30, n is unconditionally incremented by 1, and then the counter value is checked in step S32.
Proceed to. Also, even if C-FLAG is not set, D
- If the Q output of F/F23 is set, an interrupt request of 1 is received before the external counter 16 is read, causing the interrupt to be missed. Therefore, in step S31, input port _i14 is set to " If it detects that it is H”, n is unconditionally +
1, and then proceeds to step S33.
1 and the input port _i14 is "L", the process directly advances to step S32.

Here, the check process in step S32 is necessary for the following reason. That is, as described above, from the start of INT0 processing, the external counter 16
There is a delay of y ₂ before the value of is read. This is due to the number of instruction machine cycles from start to read. Therefore, the first
As shown in Figure 4, if an interrupt request of 1 is made between the start of mth INT0 and the reading of the counter, 1 will be prohibited until the calculation and display are finally completed, so n will be 1. The count ends up being low. Therefore, it is checked whether the value x of the external counter 16 is smaller than the count value _x1 , which corresponds to the number of machine cycles from the start of INT0 to the counter reading. In other words, we add +1 to .

After correcting the value of n according to the timing in this way, the value of the period T expressed by the above equation (3) is calculated in step S34. In this equation (3), n・t
The term +x can be directly obtained as a series of data concatenated with the value x of the external counter 16 using the value of the number counter N as the upper bit.

Further, the process of averaging the values T obtained in this manner is performed as follows. That is,
As mentioned above, the output frequency of musical instruments such as guitars has a fluctuation of about 0.5%, so displaying this as it is will not allow you to tune with 0.05% accuracy, which is the initial goal. is completely impossible, and some kind of averaging process is required here.

As mentioned earlier, according to the measurement method in this embodiment, the period T is measured by averaging several pulses of the original frequency, so averaging has been achieved to a certain extent. However, for long-term fluctuations that exceed the measurement period of T, the data will still be displayed in a fluctuating manner. And to reduce this fluctuation,
It is possible to do this by making the measurement period sufficiently long, but on the other hand, there is a problem with the response speed, so this measurement period cannot be made unnecessarily long. According to experiments, in the case of a guitar, the upper limit of this measurement period is about 0.2 to 0.3 seconds.

Considering the ease of use as a tuner based on these matters, when the measured frequency deviates significantly from the center frequency, emphasis should be placed on responsiveness, and when it is somewhat close to the center frequency, the averaging period should be lengthened. It is considered that an averaging method that satisfies the condition of suppressing fluctuations by increasing the That is, when the rough tuning is completed, the measurement period is equivalently lengthened by averaging to suppress fluctuations.

However, as a practical means of averaging the levers,
A method is adopted in which the cumulative average value of the measurement data up to the previous time and the average value of the current measurement data are taken, and this process is executed in steps S35 to S41.
That is, in step S35, A is selected which indicates that the period T is within a certain range around the center frequency period _T0 .
-FLAG is checked, and this A-FLAG is set and reset in steps S39 to S41 based on the cumulative average value of the measurement cycles up to the previous time, and the cumulative average value T is within a certain range.
It is set if T ₁ <T < T ₂ , and reset otherwise. Also, in step S35,
- If FLAG is set, step S3
6. Go to S37 and perform averaging calculation T←(T+
Execute T′)/2. Here, T' is the cumulative average value up to the previous time. Next, in step S38, the obtained T is transferred as the cumulative average value T',
At the same time, the aforementioned set/reset of A-FLAG is determined and executed based on the value of T.

The arithmetic processing for obtaining display data from the value of T obtained and averaged in this way is performed as follows. Generally, this type of tuner uses cents C as a display unit, and conversion to cents is defined as C=1200log ₂ (f/f ₀ ) (5). As can be seen from this equation (5), f
If it matches f ₀ , it will be 0 cents, and the deviation of a semitone will be 100 cents. Transforming equation (5), C=1200log ₂ (f/f ₀ ) = −1200log ₂ (f ₀ /f) = −1200log ₂ (f ₀・T/m) = −1200log ₂ (f′ ₀・T) . . . (6), and the contents in the box are the multiplications of T and the preset number _f'0 , and this multiplication is executed in step S42. Since the calculation time for logarithmic conversion is limited, a table reference method is used for logarithmic conversion. That is, Z
=f′ ₀・Calculate the value of T and the value of C in advance,
Store it in ROM as a correspondence table and proceed to step S.
According to the value of Z obtained by the calculation in step S42, the corresponding value of C is obtained, and this process is executed in step S43.

Further, the display data obtained through this processing is output and displayed on the indicator 22 in step S44, and then the number counter and pulse counter are initialized to "0" in steps S45 and S46, and the display data is outputted and displayed on the indicator 22 in step S47. After setting FLAG, it enters the standby state for the next measurement. Thereafter, the processing operations of steps S44 to S48 are repeatedly executed.

Although the above embodiment has been described with reference to the case where the present invention is applied to tuning a guitar, it goes without saying that the present invention can also be applied to tuning pianos and other musical instruments.

As described in detail above, according to the present invention, the number of cycles of a signal synchronized with the fundamental wave component included in the sounding body to be tuned is measured during a predetermined interval, and the amount of deviation from the reference scale frequency signal cycle is calculated. In the case of detection by the central processing unit, when the frequency of the signal corresponding to the sounding body falls within a certain range around the tuning center frequency, the cycle of averaging processing of the measurement data is lengthened. Therefore, we can minimize the difficulty in reading the indicator due to fluctuations in the measurement frequency, and also eliminate instability due to fluctuations in R, C, etc., providing this type of highly practical tuning device. It is possible.

[Brief explanation of drawings]

Figure 1 is a circuit block diagram showing a conventional tuner.
Fig. 2 is an operating waveform diagram of each part of Fig. 1, Fig. 3 is a circuit block diagram showing an embodiment of the tuner according to the present invention, Fig. 4 is a circuit diagram showing an example of the same synchronous oscillator, and Fig. 5 6, 7, 8, 9, 10, and 14 are operational waveform diagrams of the circuit shown in FIG. 3, and FIG. 11, FIGS. 12 and 13 are flowcharts of the same. 2...Amplifier, 10...Synchronous oscillator, 11...
Free-running frequency setting circuit, 11a to 11f...resistance,
12... Tuning string designation circuit, 12a to 12f... String designation switch, 13... Central processing unit, 14
...Oscillation circuit, 15...Crystal resonator, 16...Counter, 17a, 17b...Inverter, 18...
...Nandgate, 19...Flip Flop.

Claims (1)

[Claims] 1. A signal sending circuit that oscillates a signal synchronized with the fundamental wave component included in the sounding body to be tuned, and setting an oscillation constant in the signal sending circuit according to the pitch of the sounding body to be tuned. a central processing unit that calculates the difference between the frequency of the fundamental wave component of the musical tone signal and the reference frequency of the tuned sounding body as tuning measurement data; display means for displaying the tuning state of the sounding body, and for averaging the tuning measurement data when the frequency of the signal sent from the signal sending circuit falls within a certain range around the tuning center frequency of the sounding body. 1. A tuner characterized in that a processing means for lengthening the measurement cycle of the central processing unit is added to the central processing unit.