JP2005024997A - Stringed instrument and effect device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stringed instrument and an effect device that impart such an effect that resonance of the body of the stringed instrument is faithfully reproduced in the output of a piezoelectric pickup. <P>SOLUTION: An inputted digital signal is filtered by a low-pass filter 50 whose cutoff frequency is about 3 kHz and has its frequency characteristic varied by an FIR filter 45 at a sampling frequency of 6.5 kHz. The inputted digital signal is filtered by a high-pass filter 60 whose cutoff frequency is about 5 kHz and has its level adjusted, and the output of the FIR filter 45 is added to the level-adjusted signal. Consequently, body resonance of an acoustic guitar or the like is efficiently and faithfully reproduced. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a stringed musical instrument and an effect device that give an optimal effect to the one that converts string vibration of a stringed musical instrument into an electrical signal by a piezoelectric pickup.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there has been known a device that extracts string vibration of a stringed instrument such as an acoustic guitar or a violin as an electric signal by various pickups and amplifies the electric signal or adds various effects to form a musical sound. Among these converters, a piezoelectric transducer called a piezo pickup converts the vibration of the bridge attached to the body into an electrical signal, and in the space where the sound generated by the vibration of the string is formed by the body. Insensitive to resonance. Therefore, the electric signal converted by this piezo pickup becomes a thin and inorganic musical sound without features. Although this is difficult to use as a musical tone as it is, there is an advantage that it can be easily processed into various musical tones. In the invention disclosed in Japanese Patent Laid-Open No. 2003-15644, an input signal is provided with a reverberation sound generation sequence that simulates the drumming of a musical instrument or the presence of a room in parallel and a direct sound generation sequence of an instrument in parallel. It is assumed that a natural sound such as a sound collected from an acoustic guitar or the like is collected by outputting a mixed reverberation sound and direct sound.
[0003]
[Patent Document 1]
JP 2003-15644 (FIG. 2 etc.)
[0004]
[Problems to be solved by the invention]
However, although the above-described effect device can process the vibration of the string of the stringed instrument into a natural sound to some extent, there is a problem that the resonance caused by the body of an acoustic guitar or the like cannot be faithfully reproduced.
[0005]
The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide a stringed instrument and an effect device that impart an effect of faithfully reproducing the resonance of the stringed instrument body to the output of the piezoelectric pickup. It is said.
[0006]
[Means for Solving the Problems]
In order to achieve this object, a stringed instrument according to claim 1 is a digital pickup that samples a piezoelectric pickup that converts string vibration of a stringed instrument into an electric signal and an electric signal converted by the piezoelectric pickup at a predetermined sampling period. A converter for conversion and an FIR filter through which a digital signal converted by the converter passes are provided.
[0007]
According to the stringed instrument of the first aspect, the string vibration of the stringed instrument is converted into an electric signal by the piezoelectric pickup, sampled at a predetermined sampling period and converted into a digital signal, and the timbre is changed or given by the FIR filter.
[0008]
The stringed instrument according to claim 2 is the stringed instrument according to claim 1, wherein the coefficient of the FIR filter is obtained by an impulse response of the body of the stringed instrument.
[0009]
A stringed instrument according to claim 3 is the stringed instrument according to claim 1 or 2, wherein a plurality of sets of coefficients of the FIR filter are stored, and a filter coefficient selection means for selecting any one of the stored sets. It has.
[0010]
According to the stringed instrument of claim 3, a plurality of sets of coefficients of the FIR filter are stored, and any one of the stored sets is provided with selecting means, and the body of various stringed instruments is provided. A selection means for storing a plurality of sets of coefficients obtained from the impulse response and selecting from among them is provided.
[0011]
Stringed instrument according to claim 4, the transducer in the stringed instrument according to any one of claims 1 to 3 is provided with a low pass filter low-frequency component of the electrical signal converted by the piezoelectric pick-up passes, the The signal that has passed through the low-pass filter is sampled at a predetermined sampling period and converted into a digital signal.
An output means comprising a high-pass filter through which a high-frequency component of the electrical signal converted by the piezoelectric pickup passes, and synthesizing and outputting a musical sound signal that has passed through the FIR filter and a musical sound signal that has passed through the high-pass filter And.
[0012]
According to the stringed instrument of the fourth aspect, the low-pass filter through which the low-frequency component of the electrical signal converted by the piezoelectric pickup passes, and the signal that has passed through the low-pass filter is processed or processed by the FIR filter. It is added and synthesized with the musical tone signal that has passed through the high-pass filter through which the high-frequency component passes.
[0013]
The stringed musical instrument according to the fifth aspect is operated by the FIR filter after passing through the low-pass filter, and the calculation is performed based on the sampling frequency corresponding to the cutoff frequency of the low-pass filter.
[0014]
The effect device according to claim 6 is a low-pass filter through which a low-frequency component of an input musical sound signal passes, an FIR filter through which a digital signal having a predetermined sampling period that has passed through the low-pass filter passes, A high-pass filter through which a high-frequency component of the input musical sound signal passes, an output means for synthesizing and outputting the musical sound signal that has passed through the FIR filter and the musical sound signal that has passed through the high-pass filter.
[0015]
The effect device according to claim 7 is the effect device according to claim 6, wherein the cutoff frequency of the high-pass filter is set so as to compensate for the band cut off by the low-pass filter.
[0016]
The effect device according to claim 8 is the effect device according to claim 6 or 7, wherein the coefficient of the FIR filter is obtained by an impulse response of a stringed instrument body.
[0017]
The effect device according to claim 9 is the effect device according to any one of claims 6 to 8, further comprising filter coefficient selection means for storing a plurality of sets of coefficients of the FIR filter and selecting any one of the sets. .
[0018]
In the effect device according to the tenth aspect, the calculation by the FIR filter is performed after passing through the low-pass filter, and the calculation is performed based on the sampling frequency corresponding to the cutoff frequency of the low-pass filter.
[0019]
【The invention's effect】
According to the stringed instrument of the first aspect, since the timbre is processed or imparted by the FIR filter to the electric signal converted by the piezoelectric pickup, even if the characteristic is complicated such as the frequency characteristic of the body of an acoustic guitar, There is an effect that torso etc. can be faithfully reproduced.
[0020]
According to the stringed instrument of the second aspect, in addition to the effect produced by the stringed instrument of the first aspect, the coefficient of the FIR filter is obtained by the impulse response of the trunk of an acoustic guitar or the like. There is an effect that can be obtained.
[0021]
According to the stringed instrument according to claim 3, in addition to the effect of the stringed instrument according to claim 1 or 2, means for storing a plurality of sets of coefficients of the FIR filter and selecting any one of the plurality of sets Therefore, there is an effect that the performer can arbitrarily select a favorite tone color.
[0022]
According to the stringed instrument of claim 4, in addition to the effect of the stringed instrument according to any one of claims 1 to 3, the FIR filter is applied to the low frequency component of the electrical signal converted by the piezoelectric pickup, Since it is configured to synthesize the passed signal and the high frequency component of the electrical signal, the FIR filter is applied to the characteristic frequency band of the stringed torso of the stringed instrument to synthesize the high frequency component of the musical tone due to the string. Therefore, it is possible to simulate the stringing of stringed instruments efficiently.
[0023]
According to the stringed instrument of the fifth aspect, in addition to the effect of the stringed instrument according to the fourth aspect, the calculation of the FIR filter is performed at the sampling frequency based on the cutoff frequency of the low-pass filter. This has the effect of reducing the number and the number of operations.
[0024]
According to the effect device of the sixth aspect, the low frequency component of the input musical sound signal is subjected to the FIR filter, and the signal that has passed through the FIR filter and the high frequency component of the musical sound signal are synthesized. Therefore, there is an effect that the stringing of the stringed instrument can be realized faithfully and various stringed instruments can be simulated by the combination ratio with the high frequency component of the string signal.
[0025]
According to the effect device according to claim 7, in addition to the effect produced by the effect device according to claim 6, the cutoff frequency of the high-pass filter is set so as to compensate for the band cut off by the low-pass filter. Therefore, there is an effect that a balanced tone can be obtained in all bands.
[0026]
According to the effect device according to claim 8, in addition to the effect produced by the effect device according to claim 6 or 7, the coefficient of the FIR filter is obtained by the impulse response of the body of the stringed instrument. There is an effect that can be obtained.
[0027]
According to the effect device described in claim 9, in addition to the effect produced by the effect device according to any of claims 6 to 8, a plurality of sets of coefficients of the FIR filter are stored, and any one of the plurality of sets is stored. Since the means for selecting a set is provided, there is an effect that the performer can arbitrarily select a favorite tone color.
[0028]
According to the effect device of the tenth aspect, in addition to the effect produced by the effect device according to any one of the sixth to ninth aspects, the calculation of the FIR filter is set to the sampling frequency based on the cutoff frequency of the low-pass filter. Therefore, there are effects that the number of coefficients of the FIR filter can be reduced and the number of operations can be reduced.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is an overall block diagram of a stringed musical instrument or effect device according to an embodiment of the present invention.
[0030]
A plurality of strings stretched on the stringed instrument are fixed to a bridge provided in the resonance drum, and a piezo pickup 1 is provided below the bridge to convert the vibration of the string into an analog electric signal. This analog electric signal is pre-emphasized by the filter 2. This is performed in order to improve the S / N ratio of the high frequency component. The A / D converter 3 quantizes the digital signal with a predetermined sampling frequency (for example, 44.1 kHz), converts the signal into a digital signal, and performs various signal processing by a DSP (digital signal processor) 4. 5 is converted into an analog signal.
[0031]
The converted analog signal is de-emphasized by the filter 6, and then the CPU 10 detects the state of the bypass switch 41 (see FIG. 3) provided on the panel. If the bypass switch 41 is OFF, the FET switch 2 Is set to ON and output. When the bypass switch 41 is on, the FET switch 2 is set to off and no D / A converted signal is output. On the other hand, when the bypass switch 41 is on, the output of the piezo pickup 1 is output when the FET switch 1 is turned on, and when the bypass switch 41 is off, the FET switch 1 is set off. The output of the pickup 1 is not output directly.
[0032]
The CPU 10 is a microcomputer, executes a program stored in the ROM 13, detects mainly controls such as volumes and switches provided in the panel, and sets parameters in the DSP 4. A RAM 14, which is a memory for temporarily storing various data and the like, and an operator 12 including a display 11, a volume, a switch, and the like are connected to the CPU 10.
[0033]
FIG. 2 is a block diagram of functions executed by the DSP 4. First, the digital signal input from the A / D converter 3 is de-emphasized by the digital filter 21. This is for improving the S / N ratio of the high frequency component. Next, the acoustic modeling unit 22 gives effects such as the sound of an acoustic guitar, and this processing is the present invention. Next, the equalizer 23 corrects the frequency characteristic according to the user's instruction and applies it to the notch filter 24. This notch filter 24 is for lowering the level of the frequency that causes howling so that the musical sound input by the piezo pickup 1 does not cause howling. Next, a reverberation sound is applied by the reverb 25, and then pre-emphasis is performed by the digital filter 26 for output to the D / A converter 5 in order to improve the S / N ratio of the high frequency component.
[0034]
Next, a panel diagram of the effect device of the present embodiment will be described with reference to FIG. This panel diagram is provided in a separate housing from the stringed instrument and is configured to be placed on the floor so that you can operate the switch with your foot. It is also possible.
[0035]
The level knob 31 is a knob for adjusting the output level of the effect device, and the reverb knob 32 is for adjusting the level of the reverberant sound provided by the reverb 25. A body type switching rotary switch 33 (hereinafter referred to as a body type knob 33), a body knob 34, and a string enhancement knob 35 are operators for setting parameters of the acoustic modeling unit 22, and will be described in detail later. The equalizer section is provided with a base knob 36, a middle knob 37, and a treble knob 38. The equalizer 23 has a base knob 36 as a low band, a middle knob 37 as a middle band, and a treble knob 38 as a high band. The level of is adjusted.
[0036]
The bypass switch 41 is a switch that selects whether to apply an effect to an input signal or to output the signal without applying it. As described above, when this switch is turned on, an input signal that does not have an effect is output. When turned off, a signal with an effect is output.
[0037]
By operating the four foot switches 40, the effect is given by the parameter set by the knob of the panel, the effect is given by the parameter set in the patch stored in the memory, or , You can choose any patch among multiple patches. The name of the selected patch is displayed on the display 39. Since these details are not related to the present invention, the detailed description thereof is omitted.
[0038]
FIG. 4 shows an example of the frequency characteristic of the drumming of an acoustic guitar and its impulse response. FIG. 4A shows the frequency Hz on the horizontal axis and the logarithm of the level on the vertical axis. As can be seen from this figure, a peak is formed in the vicinity of 100 Hz to 300 Hz, and a complicated frequency characteristic is shown between 300 Hz and 3 kHz. FIG. 4B shows the impulse response of such a cylinder having frequency characteristics, with the horizontal axis representing time and the vertical axis representing level. There are various known methods for obtaining this impulse response. A microphone is installed in the vicinity of the sound hole of the torso, and a small hard ball or the like collides with a predetermined position of the torso only once. It is recorded. Although the impulse response lasts for several tens of milliseconds, an impulse response of about 10 milliseconds from the generation of the impulse is sufficient to reproduce the general acoustic guitar drumming.
[0039]
In addition, since the characteristic frequency characteristic of the body of an acoustic guitar exists between 100 Hz and around 3 kHz, the sampling frequency is set to 6.5 kHz, and 65 impulse responses of 10 milliseconds after the generation of the impulse are generated. Let the amplitude value be the coefficient of the FIR filter. If the number of coefficients is large, the characteristics up to the high frequency range can be controlled. However, if the number of coefficients is large, the calculation of the DSP is burdened.
[0040]
FIG. 5 is a block diagram of the acoustic modeling unit 22 processed by the DSP, and is configured based on the above conditions.
[0041]
The input digital signal is sampled at a sampling frequency of 44.1 kHz, and is first filtered to a frequency component of about 3 kHz or less by a low-pass filter 50 having a cutoff frequency of about 3 kHz. This is to limit the frequency component of the input signal to half or less of the sampling frequency in order to set the sampling frequency in the FIR filter to 6.5 kHz (referred to as decimation). The low-pass filter (low-pass filter) 50 is constituted by an IIR filter. Next, the correction filter 51 is passed. The filter 51 is used when it is desired to correct the characteristics of the FIR filter 45. The filter 51 has a flat characteristic or a low cut characteristic according to the characteristic of the FIR filter, and is constituted by an IIR filter.
[0042]
Thus, the amplitude value of the digital signal limited to a band of about 3 kHz or less is sequentially stored in the ring buffer 52. This ring buffer has an area for storing 441 amplitude values, which is the number of samples corresponding to a time of 10 milliseconds, and when the ring buffer 52 is addressed from 0 to 440, the first amplitude value is address 0. The next amplitude value is sequentially stored as address 1, the 441th amplitude value is stored at address 440, and the next amplitude value is overwritten again at address 0. The storage in the ring buffer 52 is performed at the sampling period, and then the filter operation is performed by the FIR filter 45.
[0043]
The FIR filter 45 includes the ring buffer 52, a multiplier 53, and an adder 54. First, 65 of the 441 amplitude values stored in the ring buffer 52 are multiplied by 65 coefficients of the FIR filter 45 by the multiplier 53. Specifically, if the address of the amplitude value stored in the latest ring buffer 52 is p, the first coefficient of the FIR filter is multiplied by the amplitude value stored in this address p, and the nth of the FIR filter The coefficient is rounded to the value (n−1) × 440 ÷ 64, and multiplied by the amplitude value stored at the address obtained by subtracting this value from p (adding 441 if this value is negative). The 65 products thus obtained are sequentially added by an adder 54, and an amplitude value whose frequency characteristics are changed by an FIR filter 45 is obtained.
[0044]
The amplitude value obtained in this way is multiplied by a coefficient set by a body knob 34 provided on the panel by a multiplier 55 and output to an adder 58. The latest amplitude value is multiplied by a coefficient set by the body type knob 33 by the multiplier 66, and then multiplied by a coefficient set by the body knob 34 by the multiplier 56. The body knob 34 is set so that the effect of the body resonance is enhanced as the knob is turned to the right. When the body knob is turned to the right, the coefficient of the multiplier 55 is increased and the coefficient of the multiplier 56 is decreased. It is set as follows. Thus, the frequency characteristic of 3 kHz or less is changed by the FIR filter 45, and the intensity of the drumming can be adjusted by changing the mixing ratio with the original signal. The output of the multiplier 55 and the output of the multiplier 56 are added by the adder 58, and the coefficient set by the body type knob 33 is also multiplied by the multiplier 64 and output to the adder 59.
[0045]
The input digital signal passes through a high-pass filter (high-pass filter) 60 having a cutoff frequency of about 5 kHz, is multiplied by a coefficient set by the body type knob 33 by a multiplier 61, and an adder 59 Is output. As a result, the band that has passed through the low-pass filter 50 is added with the drumming by the FIR filter 45, and the band that has been cut off by the low-pass filter 50 is added to the band that has passed through the high-pass filter 60.
[0046]
The coefficients of the FIR filter 45 are known to have various characteristics depending on the type and manufacturer of the acoustic guitar. The coefficient sets of these characteristics are stored and selected by the body type knob 33 shown in FIG. Set to a fixed coefficient.
[0047]
The high-pass filter 62 has a cutoff frequency higher than that of the high-pass filter 60, and is multiplied by the coefficient set by the string enhancement knob 35 by the multiplier 63 and output to the adder 59. This is used when emphasizing the high range of a string such as a guitar. The output of the adder 59 is output with unnecessary low frequency components removed by the low cut filter 65.
[0048]
In the above embodiment, since processing other than acoustic modeling is performed as the effect device, sampling is performed at 44.1 kHz, and the FIR filter 45 is down-sampled and calculated. A second embodiment that is sampled and implemented at a sampling frequency of 5 kHz is shown below.
[0049]
FIG. 6 is a block diagram of the second embodiment of the present invention. The same reference numerals are given to the same components as those described so far. The analog electric signal converted by the piezo pickup 1 passes through an analog low-pass filter 70 having a frequency band of about 3 kHz or less, and is then quantized by the A / D converter 3 at a sampling frequency of 6.5 kHz. The quantized amplitude values are sequentially stored in a ring buffer that stores 65 amplitude values controlled by the DSP 71, and 65 amplitude values and 65 coefficients are multiplied by a multiplier by an FIR filter and added. It is added by the device. The added amplitude value is converted to an analog signal by the D / A converter 5, smoothed by the low-pass filter 72, and amplified or attenuated by the amplifier 73 with the coefficient set by the body type knob 33.
[0050]
On the other hand, the analog signal converted by the piezo pickup 1 is passed through a high-pass filter 74 having a cutoff frequency of about 5 kHz, and is amplified or attenuated by an amplifier 75 with a coefficient set by the body type knob 33. The outputs of the amplifier 73 and the amplifier 75 are synthesized and output.
[0051]
The present invention has been described above based on the embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications and changes can be easily made without departing from the spirit of the present invention. Can be inferred.
[0052]
For example, in the first embodiment, the calculation of the FIR filter is performed for the amplitude value having the sampling frequency of 6.5 kHz in the cycle of 44.1 kHz which is the sampling frequency of the original signal. A simple interpolation method may be used when performing the FIR calculation with a long period and returning to the original signal sampling frequency.
[0053]
[Brief description of the drawings]
FIG. 1 is an electric block diagram of a stringed musical instrument and an effect device according to an embodiment of the present invention.
FIG. 2 is a functional block diagram of a DSP.
FIG. 3 is a panel diagram of the effect device.
FIG. 4 is a diagram showing an example of frequency characteristics and impulse response of the body of an acoustic guitar.
FIG. 5 is a detailed view of an acoustic modeling unit.
FIG. 6 is a diagram illustrating a second embodiment.
[Explanation of symbols]
1 Piezo pickup 4 DSP
10 CPU
22 Acoustic modeling unit 33 Body type knob (filter coefficient selection means)
45 FIR filter 50 Low pass filter 60 High pass filter

Claims (10)

A piezoelectric pickup that converts string vibrations of stringed instruments into electrical signals;
A converter that samples the electrical signal converted by the piezoelectric pickup at a predetermined sampling period and converts it into a digital signal;
A stringed instrument comprising: an FIR filter through which a digital signal converted by the converter passes. The stringed instrument according to claim 1, wherein the coefficient of the FIR filter is obtained by an impulse response of a stringed instrument body. The stringed instrument according to claim 1 or 2, further comprising filter coefficient selection means for storing a plurality of sets of coefficients of the FIR filter and selecting any one of the stored sets. The converter includes a low-pass filter through which a low-frequency component of the electrical signal converted by the piezoelectric pickup passes,
A high-pass filter through which a high-frequency component of the electrical signal converted by the piezoelectric pickup passes,
2. An output means for synthesizing and outputting a musical tone signal that has passed through the FIR filter after passing through the low-pass filter and a musical tone signal that has passed through the high-pass filter. 4. The stringed instrument according to any one of 3 to 3. The stringed instrument according to claim 4, wherein the FIR filter is calculated at a sampling frequency corresponding to a cutoff frequency of the low-pass filter. A low-pass filter through which the low-frequency component of the input musical sound signal passes,
An FIR filter through which a digital signal having a predetermined sampling period that has passed through the low-pass filter passes;
And output means for outputting by synthesizing the musical tone signal high frequency component of the tone signal has passed tone signal passed through the high-pass filtering the FIR filter to pass the high-pass filter being the input An effect device characterized by that. The effect device according to claim 6, wherein a cutoff frequency of the high-pass filter is set so as to compensate for a band cut off by the low-pass filter. 8. The effect device according to claim 6, wherein the coefficient of the FIR filter is obtained by an impulse response of a stringed instrument body. The filter coefficient selecting means for storing a plurality of sets of coefficients of the FIR filter and selecting any one of the stored sets is provided. Effect device. The effect device according to any one of claims 6 to 9, wherein the FIR filter is operated at a sampling frequency corresponding to a cutoff frequency of the low-pass filter.

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