Abstract:
The tuning device also includes an input unit for inputting a sound of an instrument to be tuned or a musical sound signal, a conversion information storing portion in which a plurality of pieces of information on filters for tuning are stored, a control unit for extracting the piece of information on an arbitrary one of the filters from the conversion information storing portion, and a conversion unit for converting a signal of the input unit into a signal of an arbitrary frequency band in response to a signal from the control unit. Owing to this structure, even if ambient noise has mixed with a sound of the instrument to be tuned, the sound is filtered into a signal component of a target scale or a target pitch name. By extracting a pitch from this signal component, the number of erroneous tuning operations can be reduced.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a tuning device for measuring and displaying a difference between a fundamental frequency of an instrumental sound or a musical sound signal and a reference frequency serving as a criterion for comparison. 
   2. Description of the Related Art 
   It has been generally known to remove a certain quantity of unnecessary components such as noise and harmonic components outside a range enabling the tuning of an instrument sound or a musical sound signal (i.e., a range from low pitch sounds to high pitch sounds) by means of a passive filter composed of a resistor and a capacitor, an active filter constructed of an operational amplifier, or the like, as disclosed in JP 9-6341 A (page, 4 FIG. 1). 
   A conventional tuning device is a fixed filter designed to remove noise and harmonic components outside a tuning-permitting range (i.e., a tonal range from low pitch sounds to high pitch sounds) and thus cannot exercise a filtering effect on unnecessary sounds within a range enabling the tuning of sounds other than those of an instrument to be tuned. As this phenomenon, it is possible to mention tuning in an environment surrounded by many instruments as in the case of, for example, a brass band. In such an environment, the tuning device is susceptible to the influence of ambient sounds and quite often makes an erroneous determination as a response to sounds of an instrument to be tuned. 
   Further, there is also a method of performing tuning by attaching a piezoelectric pickup to an instrument to avert the influence of ambient sounds and inputting an output signal from the piezoelectric pickup. However, the piezoelectric pickup may pick up not only the musical sounds to be tuned but also the sounds of other instruments in the neighborhood, including brass instruments resounding at high volume, as conductive noise. This constitutes a factor behind erroneous determinations made by the tuning device. 
   Still further, in the case of Taisho harps or in school lessons, there are often several performers lined up along a single desk to play instruments. In tuning the instruments in such situations, the above-mentioned conductive noise or vibrating sound causes erroneous determinations noticeably. 
   SUMMARY OF THE INVENTION 
   In consideration of the aforementioned circumstances, it is an object of the present invention to provide a tuning device capable of reducing the number of erroneous determinations on tuning resulting from noise. 
   A tuning device of the present invention has a conversion means for converting a signal inputted from the outside into a signal within a desired frequency band, a conversion information storing portion in which parameters corresponding to a filter suited for a frequency of a scale or pitch name as a tuning target are stored, and a control means for controlling the conversion means on the basis of a desired piece of information fetched from the conversion information storing portion. Owing to this structure, even if ambient noise has mixed with a sound of an instrument to be tuned, filtering can be carried out to obtain a signal similar to a signal component of a target scale or pitch name. By extracting a pitch from the signal, the number of erroneous operations in tuning is reduced. 
   The tuning device has such a feature that tuning can be carried out quickly and reliably even in a tumultuous environment by making it difficult to affect the tuning of the instrument within a range of the scale or pitch name as a tuning target. Further, if a user has a plurality of instruments, he or she sets the conversion means to a frequency band matching a selected mode such as an instrument to be tuned from the outside via an input means or a string of a stringed instrument. By performing a tuning operation taking account of a tonal range of the instrument, the user can accurately tune the instrument with little influence of ambient noise. This is another feature of the present invention. 
   Furthermore, according to the present invention, more accurate tuning can be carried out with little influence of external noise by selecting a chromatic pitch name as a tuning target within a narrower range than a tonal range of an instrument and setting the conversion means to a frequency band corresponding to the selected pitch name. This is still another feature of the present invention. 
   In the tuning device of the present invention, appropriate filtering can be carried out for a signal component of a scale or pitch name of an inputted instrumental sound. In addition, by repeating this operation, an optimal filter processing performance of automatic follow-up type is obtained along with an operation of reducing the influence of ambient noise. By extracting a pitch from the signal of the instrumental sound under such an operation, an effect of reducing the number of erroneous operations in tuning is achieved even in an environment plentiful in ambient noise. 
   Further, by conducting a desired setting as to, for example, an instrument to be tuned or a chromatic pitch name via the setting portion from the outside, an optimal filter processing is performed for a set tonal range. Thus, an operation of reducing the influence of ambient noise for an inputted instrumental sound is obtained. By extracting a pitch from a musical sound under such an operation, the number of erroneous operations in tuning is reduced. As a result, an effect of enabling accurate tuning even under an environment plentiful in instruments and susceptible to the influence of noise is achieved. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings: 
       FIG. 1  is a block diagram showing a structure of a tuning device according to the present invention; 
       FIG. 2  is a block diagram showing a second embodiment; 
       FIG. 3  is a table; 
       FIG. 4  is an explanatory diagram of a filter; 
       FIG. 5  is a flowchart of a main routine; 
       FIG. 6  is a flowchart for setting a filter; 
       FIG. 7  is a flowchart of a main routine of the second embodiment; and 
       FIG. 8  is a flowchart for setting a filter in the second embodiment. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Embodiments of a tuning device according to the present invention will be described in detail with reference to the drawings. 
     FIG. 1  is a block diagram showing a structure of a tuning device to which the present invention is applied. A microcomputer  2  controls the overall operation of this tuning device. The microcomputer includes a memory  2 D that is composed of a read-only memory in which a program for controlling the operation of the entire tuning device and the like are stored, a random access memory as a working area required in executing the program, and the like. 
   A musical sound inputting portion  1 A as an input means  1 , which is a member for inputting an electric signal of a sound emitted from an instrument, is composed of a microphone for converting a sound into an electric signal, a jack for inputting an electric signal of an instrument, and the like. An amplifier  1 B, which is a low-frequency amplifier for amplifying an electric signal of the musical sound inputting portion  1 A, outputs an amplified musical sound signal S 1  to a conversion means  3 . 
   The conversion means  3 , which is a filter circuit to be described later, outputs to a waveform shaping portion  4  an electric signal S 2  with a certain frequency band that has passed a desired filter based on a conversion information storing portion  2 E. Filter information as shown in a later-described table of  FIG. 3  is stored in the conversion information storing portion  2 E. In response to a signal outputted from the conversion means  3 , the waveform shaping portion  4  outputs a waveform-shaped electric signal S 3  (rectangular wave) to the MCU (microcomputer)  2 . 
   A pitch extracting portion  2 A as a pitch extracting means, a retrieval means  2 B, a cent value calculating portion  2 C, the memory  2 D, the conversion information storing portion  2 E, and a control means  2 F are preferably structured as a microcomputer. 
   The pitch extracting portion  2 A measures a time interval every time a rectangular wave as indicated by an electric signal S 3  rises or falls, and extracts the electric signal S 2 , that is, a pitch (cycle) of the musical sound signal S 1 . A signal with the extracted pitch is outputted to the retrieval means  2 B. 
   The retrieval means  2 B compares the signal with the extracted pitch with pieces of reference cycle data on octave (an interval with full 8 degrees) and pitch name (a designation allocated to each of 12 different sounds contained in each octave) as stored in the memory  2 D, and calculates a chromatic (a designation allocated to each of 12 semitones constituting one octave, namely, an interval with full 8 degrees) pitch name from that piece of reference cycle data which is similar to the extracted pitch. The retrieval means  2 B outputs a calculated chromatic signal to the cent value calculating portion  2 C and the control means  2 F, and outputs a pitch signal to the cent value calculating portion  2 C. 
   In response to the chromatic semitone signal retrieved by the retrieval means  2 B, the cent value calculating portion  2 C reads a piece of reference data on one cent of a relevant semitone from pieces of reference data corresponding to respective cents (each representing an interval of more or less a hundredth part of a chromatic semitone) of chromatic semitones stored in the memory  2 D. Further, the cent value calculating portion  2 C calculates a cent value for the chromatic semitone on the basis of the piece of reference data on the relevant semitone and the signal with the extracted pitch, and outputs the cent value to the control means  2 F. 
   In response to the signals outputted from the retrieval means  2 B, the cent value calculating portion  2 C, and the like, the control means  2 F outputs to the display portion  5  a signal for displaying pieces of tuning information such as octave, pitch name, and cent value. 
   The display portion  5  performs its display function in the form of a pointer-type meter, a liquid crystal display element, or an LED element. 
   The tuning device structured as described above can also be carried around if a portable battery such as an electric cell is used as a power source. 
   The operation of the tuning device will be described hereinafter. 
   In the conversion information storing portion  2 E, pieces of information on conversions carried out for instrument models, octaves, and pitch names, and pieces of information on filters are stored for several kinds of frequency bands, for example, as is apparent from the table shown in  FIG. 3 . 
   In response to a chromatic semitone signal from the retrieval means  2 B, the control means  2 F reads a piece of information on frequency band from the conversion information storing portion  2 E based on the table of  FIG. 3  corresponding to the signal. Further, the control means  2 F outputs the read piece of information to the conversion means  3  and sets the conversion means  3  within a desired frequency band. 
   A switched capacitor filter can be mentioned as an example of the conversion means  3 . It should be noted herein that the term “switched capacitor” means a method of obtaining a characteristic such as variable resistance by controlling an analog switch in an on-off manner with clock pulses by use of the analog switch and a capacitor in combination. The switched capacitor filter is a variable filter utilizing this method and can handle various filter characteristics including band-pass and low-pass characteristics. For clock pulse control or filter control, a microcomputer is often used. Alternatively, as another example of the conversion means  3 , a digital filter performing time-division processings can also be utilized. In the case where the conversion means  3  is a switched capacitor filter, pieces of information on frequency band and pieces of information on clock pulses corresponding to tonal ranges, various filter characteristics, and the like are outputted from the control means  2 F. 
   An example of this desired filter will be described with reference to  FIG. 3 . 
     FIG. 3  is a table showing exemplary parameters of band-pass filters for chromatics. Each value A in the leftmost column represents an exemplary tonal range from low tones starting with a pitch name C (000000) in the fourth octave to high tones ending with a pitch name B (100011) in the sixth octave. The value A corresponds to an address of the conversion information storing portion  2 E. Shown to the right of this value A are instrument models as data, an octave, a pitch name, and a corresponding center frequency F 0  in this order. Shown to the right of this center frequency F 0  are parameters of a band-pass filter illustrated in  FIG. 4 , namely, a low-pass cut-off frequency Fc+ (F 0 +α) obtained by adding α to the center frequency F 0 , a high-pass cut-off frequency Fc− (F 0 −α) obtained by subtracting α from the center frequency F 0 , and a switching clock pulse (β, γ, δ) in this order. In an actual operation, a preferred filter coefficient is assigned and a filter response (which is called a filter gradient and assigned to, for example, the item of “other” in the column on the right side in  FIG. 3 ) or the like is given. Thus, in response to a signal from the control means  2 F, the conversion means  3  outputs the electric signal S 2 , which is less susceptible to a malfunction in pitch extraction resulting from noise reduction than the electric signal S 1 , to the waveform shaping portion  4 . 
   This series of operations will be described as to respective steps with reference to flowcharts of  FIGS. 5 and 6 . 
     FIG. 5  shows a main routine of the tuning device of the present invention. 
   An initialization step S 100  in  FIG. 5  represents a processing performed upon activation of the tuning device to initialize various buffers, registers, parameters, and the like. In this step, the setting of the conversion means  3 , that is, the filter is initialized as well. In this case, it is desirable to initialize the filter according to a flat characteristic for an operational range of the tuning device. After the initialization step S 100  has been terminated, a transition to a first pitch extracting step S 101  is made. 
   The first pitch extracting step S 101  is a processing of extracting a first pitch. This step is intended to extract a pitch of an inputted musical sound and subject the pitch of the musical sound to an adjustment starting from the initialization of the filter. After the first pitch extracting step S 101  has been terminated, a transition to a first musical sound retrieving step S 102  is made. 
   The first musical sound retrieving step S 102  is a first musical sound retrieving processing performed to retrieve a notation of a chromatic semitone from the pitch extracted in the first pitch extracting step S 101 . In this case, it is also acceptable to calculate a cent value while the notation of the semitone is retrieved. After the processing of the first musical sound retrieving step S 102  has been terminated, a transition to a first filter setting step S 103  is made. 
   The first filter setting step S 103  is a filter setting routine to be described later. This step is intended to set the filter again in a preferred manner, for example, to a frequency close to that of the inputted musical sound, after the filter has been initialized (according to the flat characteristic for a tuning range). After the processing of this step has been terminated, a transition to a second pitch extracting step S 104  is made. 
   The second pitch extracting step S 104  is a processing of extracting a second pitch. This step is intended to ensure extraction of a stable pitch via the filter set again in the first filter setting step S 103 . After the processing of the second pitch extracting step S 104  has been terminated, a transition to a step S 105  is made. 
   The step S 105  is a second musical sound retrieving processing performed to retrieve a notation of a chromatic semitone from the pitch extracted in the second pitch extracting step S 104 . In this case as well, it is acceptable to calculate a cent value while the notation of the semitone is retrieved. After the processing of the step S 105  has been terminated, an operation confirming step S 106  is made. 
   The operation confirming step S 106  is a processing of confirming tuning stability on the basis of the extracted pitch and the result of retrieval of the musical sound. If tuning is unstable, a transition to a second filter setting step S 107  as a routine of setting a filter is made. If tuning is stable, a transition to a step S 108  is made. 
   The step S 108  is a display processing of causing the display portion  5  to display a tuning state of the inputted musical sound. This main routine ends with the step S 108 . By repeating this main routine each time the processing of inputting a musical sound is performed, a filtering effect with an automatic follow-up to the musical sound is achieved. Consequently, the more stable extraction of a pitch is made possible. 
   The first filter setting step S 103  and the second filter setting step S 107  are routines of setting the filter, which will be described with reference to  FIG. 6 . In a step S 200  of  FIG. 6 , for example, an acquired pitch, the notation of a semitone, and pieces of information on the setting of the filter are obtained from a table of the parameters as shown in  FIG. 3 . After the processing of the step S 200  has been terminated, a transition to a step S 201  is made. In the step S 201 , it is confirmed whether or not the filter has been changed from its initialized state and whether or not there has been a change in the setting of the filter since the execution of a routine activated as a result of tuning unstableness. Even if only a part of the setting of the filter has been changed, a transition to a step S 202  is made. If the same state as the last time has been maintained, namely, if no change has been made, a withdrawal from this routine is made. 
   The step S 202  is a processing of setting a suitable filter selected from various filters such as a band-pass filter, a low-pass filter, and a high-pass filter with the aid of the parameters processed in the step S 200 . After the processing of the step S 202  has been terminated, a transition to a step S 203  is made. 
   The step S 203  is a processing of confirming whether or not the band-pass filter has been selected. If the band-pass filter has been selected, a transition to a step S 204  is made. If not, a transition to a step S 207  is made. 
   In the step S 204 , the setting of a high-pass side (for cutting low frequencies) of the band-pass filter is made. After this processing has been terminated, a transition to a step S 205  is made. 
   In the step S 205 , the setting of a low-pass side (for cutting high frequencies) of the band-pass filter is made. After the processing of the step S 205  has been terminated, a transition to a step S 206  is made. In setting the band-pass filter, the processings of the steps S 204  and S 205  may be permutated. 
   The step S 207  is a processing of confirming whether or not the high-pass filter has been selected. If the high-pass filter has been selected, a transition to a step S 208  is made. If not, a transition to a step S 209  is made. 
   In the step S 208 , the high-pass filter is set. After this processing has been terminated, a transition to the step S 206  is made. 
   The step S 209  is a processing of confirming whether or not the low-pass filter has been selected. If the low-pass filter has been selected, a transition to a step S 210  is made. If not, a transition to a step S 211  is made. 
   In the step S 210 , the low-pass filter is set. After this processing has been terminated, a transition to the step S 206  is made. 
   In the step S 211 , the setting of other filters, a band elimination filter, for example, is made. 
   After the processing of the step S 211  has been terminated, a transition to the step S 206  is made. 
   The step S 206  is a processing performed in the case where the conversion means  3  uses clock pulses for controlling the switched capacitor filter or the like. The setting of clock pulses is made referring to the information acquired in the step S 200 . 
   After the processing of the step S 206  has been terminated, a withdrawal from this routine is made. Thus, the operations of the components constituting the MCU (microcomputer)  2 , namely, the conversion information storing portion  2 E, the control means  2 F, the pitch extracting portion  2 A described above, the retrieval means  2 B, the cent value calculating portion  2 C, and the memory  2 D can be realized by the aforementioned program. 
   Next, reference will be made to  FIG. 2 , which is a block diagram showing the second embodiment. In this block diagram, the musical sound inputting portion  1 A, the amplifier  1 B, the conversion means  3 , the waveform shaping means  4 , the MCU (microcomputer)  2 , the pitch extracting portion  2 A, the musical sound retrieving portion  2 B, the cent value calculating portion  2 C, the memory  2 D, the conversion information storing means  2 E, and the display portion  5  may be designed to perform the same operations as those described with reference to the block diagram of  FIG. 1 . A setting portion  6 , which is a means for performing operations of selecting an instrument to be tuned, a string of a stringed instrument, or a chromatic pitch name from the outside, is constituted by, for example, a switch circuit for generating a switch signal by opening and closing a switch member. This switch signal is outputted to the control means  2 F inside the MCU (microcomputer)  2 . In response to a signal from the setting portion  6 , the control means  2 F reads from the conversion information storing portion  2 E a piece of filter information based on the signal and outputs it to the conversion means  3 . The conversion means  3  performs the same operation as the variable filter circuit described with reference to the block diagram of  FIG. 1 . The conversion means  3  constitutes a desired filter based on an output signal of the control means  2 F, and outputs to the waveform shaping portion  4  the electric signal S 2  that has passed through the filter. 
   This series of operations will be described with reference to flowcharts shown in  FIGS. 7 and 8 . 
     FIG. 7  shows a main routine of the second embodiment. An initialization step S 300  in  FIG. 7  is a processing performed upon activation of the tuning device. In this processing, various buffers, registers, parameters, and the like are initialized. After the initialization step S 300  has been terminated, a transition to an outside information fetching step S 301  is made. 
   The outside information fetching step S 301  is a processing of fetching a piece of information received via the setting portion  6  as to an instrument to be tuned, a string of a stringed instrument, a chromatic pitch name, or the like. After the outside information fetching step S 301  has been terminated, a transition to a filter setting step S 302  is made. 
   The filter setting step S 302  is a filter setting routine to be described later. After this routine has been terminated, a transition to a pitch extracting step S 303  is made. The pitch extracting step S 303  is a processing of extracting a pitch. After this processing has been terminated, a transition to a musical sound retrieving step S 304  is made. 
   The musical sound retrieving step S 304  is a processing of retrieving a musical sound. In this processing, a notation of a chromatic semitone is retrieved from the pitch extracted in the pitch extracting step S 303 . In this case as well, it is acceptable to calculate a cent value while the notation of the semitone is retrieved. After the processing of the musical sound retrieving step S 304  has been terminated, a transition to a step S 305  is made. 
   The step S 305  is a display processing of causing the display portion  5  to display a tuning state of the inputted musical sound. This main routine ends with the step S 305 . 
   The filter setting step S 302  is a routine of setting the filter, which will be described with reference to  FIG. 8 . In a step S 400  of  FIG. 8 , pieces of information on the setting of the filter are obtained from, for example, a table of parameters as shown in  FIG. 3 , based on a piece of information received via the setting portion  6  as to an instrument to be tuned, a string of a stringed instrument, or a chromatic pitch name. After the processing of the step S 400  has been terminated, a transition to a step S 401  is made. 
   If there is a change in the setting of the filter in the step S 401 , a transition to a step S 402  is made. If the same state as the last time has been maintained, namely, if no change has been made, a withdrawal from this routine is made. 
   The step S 402  is a processing of setting a suitable filter selected from various filters such as a band-pass filter, a low-pass filter, and a high-pass filter with the aid of the parameters processed in the step S 400 . After the processing of the step. S 402  has been terminated, a transition to a step S 403  is made. 
   The step S 403  is a processing of confirming whether or not the band-pass filter has been selected. If the band-pass filter has been selected, a transition to a step S 404  is made. If not, a transition to a step S 407  is made. 
   In the step S 404 , the setting of a high-pass side (for cutting low frequencies) of the band-pass filter is made. After this processing has been terminated, a transition to a step S 405  is made. 
   In the step S 405 , the setting of a low-pass side (for cutting high frequencies) of the band-pass filter is made. After the processing of the step S 405  has been terminated, a transition to a step S 406  is made. In setting the band-pass filter, the processings of the steps S 404  and S 405  may be permutated. 
   The step S 407  is a processing of confirming whether or not the high-pass filter has been selected. If the high-pass filter has been selected, a transition to a step S 408  is made. If not, a transition to a step S 409  is made. 
   In the step S 408 , the high-pass filter is set. After this processing has been terminated, a transition to the step S 406  is made. 
   The step S 409  is a processing of confirming whether or not the low-pass filter has been selected. If the low-pass filter has been selected, a transition to a step S 410  is made. If not, a transition to a step S 411  is made. 
   In the step S 410 , the low-pass filter is set. After this processing has been terminated, a transition to the step S 406  is made. 
   In the step S 411 , the setting of other filters, a band elimination filter, for example, is made. After the processing of the step S 411  has been terminated, a transition to the step S 406  is made. 
   The step S 406  is a processing performed in the case where the conversion means  3  uses clock pulses for controlling the switched capacitor filter or the like. The setting of clock pulses is made referring to the information acquired in the step S 400 . After the processing of the step S 406  has been terminated, a withdrawal from this routine is made. 
   Thus, the operations of the components constituting the MCU (microcomputer)  2 , namely, the conversion information storing portion  2 E and the control means  2 F can be realized by the aforementioned program. A desired filtering effect can be obtained by controlling the conversion means  3 .