JPS6115625Y2 - - Google Patents
Info
- Publication number
- JPS6115625Y2 JPS6115625Y2 JP3806279U JP3806279U JPS6115625Y2 JP S6115625 Y2 JPS6115625 Y2 JP S6115625Y2 JP 3806279 U JP3806279 U JP 3806279U JP 3806279 U JP3806279 U JP 3806279U JP S6115625 Y2 JPS6115625 Y2 JP S6115625Y2
- Authority
- JP
- Japan
- Prior art keywords
- voltage
- musical tone
- tone signal
- pass filter
- output
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000001514 detection method Methods 0.000 claims description 10
- 230000007423 decrease Effects 0.000 description 7
- 238000010586 diagram Methods 0.000 description 3
- 230000005236 sound signal Effects 0.000 description 2
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000009527 percussion Methods 0.000 description 1
Landscapes
- Filters And Equalizers (AREA)
- Networks Using Active Elements (AREA)
Description
【考案の詳細な説明】
本考案は楽音信号よりその基本波周波数成分を
取り出すために使用する低域通過型フイルタの改
良に関する。[Detailed Description of the Invention] The present invention relates to an improvement of a low-pass filter used to extract the fundamental frequency component from a musical tone signal.
楽音信号は通常、基本波成分の他に多くの高調
波成分を含み、且つ振幅も時間の経過と共に大き
な変化をするのが普通であり、このような楽音信
号から基本波周波数成分を検出することは困難で
ある。このような楽音信号に対して従来行なわれ
て来た方法は、先ず楽音信号をその周波数に応じ
て適当な帯域通過型フイルタを介してその直流分
や高次の高調波成分を取り除き、更に振幅圧縮増
幅器を通過させて振幅の変化範囲を縮めてから該
楽音信号を基本波周波数検出回路に入力するとい
う複雑な手段をとつていた。 A musical tone signal usually contains many harmonic components in addition to the fundamental wave component, and the amplitude also changes greatly over time.It is difficult to detect the fundamental frequency component from such a musical tone signal. It is difficult. The conventional method for such musical tone signals is to first pass the musical tone signal through an appropriate band-pass filter according to its frequency, remove its direct current component and high-order harmonic components, and then reduce the amplitude. Complicated measures have been taken to pass the musical tone signal through a compression amplifier to reduce the range of amplitude variation before inputting the musical tone signal to a fundamental frequency detection circuit.
しかし、このような複雑な手段をもつてして
も、楽音信号の基本波周波数の帯域幅が２倍以上
に変化することが予想される場合には、前置きさ
れる帯域通過型フイルタの帯域幅をあまり狭くす
ることができないために、第２次高調波成分を多
く含む比較的周波数の低い楽音信号に対しては帯
域通過型フイルタで該楽音信号の第２次高調波成
分を阻止できないために、基本波周波数検出回路
に基本波周波数成分と第２次高調波成分とが同時
に入力し、該基本波周波数検出回路が良好に動作
し得ないことがあつた。 However, even with such complicated measures, if the bandwidth of the fundamental wave frequency of the musical tone signal is expected to change by more than twice, the bandwidth of the bandpass filter installed cannot be made very narrow, and therefore, for relatively low-frequency musical tone signals that contain many second-order harmonic components, band-pass filters cannot block the second-order harmonic components of the musical tone signals. In some cases, the fundamental frequency component and the second harmonic component are simultaneously input to the fundamental frequency detection circuit, and the fundamental frequency detection circuit cannot operate properly.
本考案は楽音信号の振幅圧縮操作を電圧制御可
変カツトオフ周波数低域通過フイルタで行なうこ
とにより、該楽音信号の基本波周波数成分の検出
が容易に行なわれる最低周波数成分を優先的に出
力する低域通過型フイルタ回路を提供するもので
ある。以下、図面を参照しながら本考案について
詳細に説明する。 The present invention compresses the amplitude of a musical tone signal using a voltage-controlled variable cut-off frequency low-pass filter, thereby preferentially outputting the lowest frequency component from which the fundamental frequency component of the musical tone signal can be easily detected. A pass-through filter circuit is provided. Hereinafter, the present invention will be described in detail with reference to the drawings.
第１図は本考案による低域通過型フイルタ回路
の回路ブロツク図である。 FIG. 1 is a circuit block diagram of a low-pass filter circuit according to the present invention.
入力端子１より楽音信号が入力されると、該楽
音信号は電圧制御可変カツトオフ周波数低域通過
フイルタ（以後VCFと称する）２によつて増幅
されて出力端子５より導出されるが、該VCF２
のカツトオフ周波数は高い周波数に設定されてい
るので、該VCF２の出力楽音信号を入力とする
振幅検出回路３は大きな出力電圧を導出し該出力
電圧を自動制御回路４に入力する。該自動制御回
路４は、入力電圧が大きい程その出力電圧が小さ
くなるように動作するので、上記振幅検出回路３
の出力電圧を入力した該自動制御回路４はその入
力電圧が大きい程上記VCF２のカツトオフ周波
数制御電圧として小さな電圧を出力する。する
と、該VCF２はそのカツトオフ周波数が低い方
に設定されるので該VCF２の出力楽音信号は上
記入力楽音信号の低域成分だけを含むものとな
り、且つその振幅も小さくなる。応じて上記振幅
検出回路３から出力される直流電圧も減少し、上
記自動制御回路４の出力電圧即ちVCF２のカツ
トオフ周波数制御電圧はそれ以上減少せず、或る
均衡のとれた値に落ち着く。 When a musical tone signal is input from an input terminal 1, the musical tone signal is amplified by a voltage-controlled variable cut-off frequency low-pass filter (hereinafter referred to as VCF) 2 and is derived from an output terminal 5.
Since the cutoff frequency of the VCF 2 is set to a high frequency, the amplitude detection circuit 3 inputting the output musical tone signal of the VCF 2 derives a large output voltage and inputs the output voltage to the automatic control circuit 4. The automatic control circuit 4 operates such that the larger the input voltage, the smaller the output voltage.
The automatic control circuit 4 to which the output voltage is inputted outputs a smaller voltage as the cut-off frequency control voltage of the VCF 2 as the input voltage is larger. Then, since the cutoff frequency of the VCF2 is set to be lower, the output musical tone signal of the VCF2 includes only the low frequency components of the input musical tone signal, and its amplitude is also small. Correspondingly, the DC voltage output from the amplitude detection circuit 3 also decreases, and the output voltage of the automatic control circuit 4, ie, the cut-off frequency control voltage of VCF2, does not decrease any further and settles at a certain balanced value.
第２図において、初期の状態におけるVCF２
のカツトオフ周波数をＡ、入力楽音信号が到来し
て低くなつた該カツトオフ周波数をＢで示す。 In Figure 2, VCF2 in the initial state
The cutoff frequency of the input musical tone signal is shown as A, and the cutoff frequency that becomes lower when the input musical tone signal arrives is shown as B.
次に、該入力楽音信号の振幅が少し減少すると
応じて振幅検出回路３の出力も減少し、自動制御
回路４の出力電圧即ちVCF２のカツトオフ周波
数制御電圧は少し増加する。このときのカツトオ
フ周波数はＣで示され、Ｂに比較して該VCF２
は入力楽音信号の基本波ｆ0に対して通過量が増
すように動作している。 Next, as the amplitude of the input musical tone signal decreases a little, the output of the amplitude detection circuit 3 also decreases, and the output voltage of the automatic control circuit 4, that is, the cutoff frequency control voltage of VCF2 increases a little. The cutoff frequency at this time is indicated by C, and compared to B, the cutoff frequency is
operates so that the amount of passage increases with respect to the fundamental wave f 0 of the input musical tone signal.
このようにVCF２の出力楽音信号は、該入力
楽音信号の一番低い周波数成分を選択するように
働き、且つまた該入力楽音信号の振幅変動に対し
ても、ほぼ一定の振幅で出力する。 In this way, the output musical tone signal of the VCF 2 works to select the lowest frequency component of the input musical tone signal, and is output with a substantially constant amplitude even with respect to amplitude fluctuations of the input musical tone signal.
更に、入力楽音信号の振幅が小さくなると、上
述と同様の経過でVCF２のカツトオフ周波数は
Ｄとなる。このカツトオフ周波数では、もはや第
２次高調波2fに対する抑制機能は殆んど失なわれ
るが、VCF２の出力楽音信号の振幅はほとんど
変化しない。しかし、これ以上の該入力楽音信号
の振幅減少に対しては該出力楽音信号の振幅も応
じて減少する傾向となる。 Furthermore, when the amplitude of the input musical tone signal becomes smaller, the cutoff frequency of VCF2 becomes D in the same manner as described above. At this cutoff frequency, the suppressing function for the second harmonic 2f is almost lost, but the amplitude of the output musical tone signal of the VCF 2 hardly changes. However, if the amplitude of the input musical tone signal decreases further, the amplitude of the output musical tone signal also tends to decrease accordingly.
しかし、入力楽音信号がピアノのような打弦楽
器や、ギターのような撥弦楽器から得られたもの
である場合は、該入力楽音信号の振幅が大きいと
きは高次の高調波を多量に含むが、応じて振幅検
出回路３の出力電圧大、自動制御回路４の出力電
圧小となるためVCF２のカツトオフ周波数が低
い方に設定されて基本波以外の高調波成分を該基
本波に対して相対的に抑制し、時間の経過と共に
該入力楽音信号の振幅が或る程度小さくなるに従
つて該入力楽音信号の波形は正弦波に非常に近く
なるので、高調波成分は抑制されないが出力端子
５より得られる出力楽音信号は常時正弦波に近い
波形を有する楽音信号つまり基本波周波数検出に
最適の出力楽音信号である。 However, when the input musical sound signal is obtained from a percussion instrument such as a piano or a plucked string instrument such as a guitar, when the amplitude of the input musical sound signal is large, it contains a large amount of high-order harmonics. , the output voltage of the amplitude detection circuit 3 becomes large and the output voltage of the automatic control circuit 4 becomes small. Therefore, the cut-off frequency of the VCF 2 is set to the lower side, and harmonic components other than the fundamental wave are set relative to the fundamental wave. As the amplitude of the input musical tone signal decreases to a certain extent with the passage of time, the waveform of the input musical tone signal becomes very close to a sine wave. The output musical tone signal obtained is a musical tone signal that always has a waveform close to a sine wave, that is, an output musical tone signal that is optimal for fundamental wave frequency detection.
以上のように、本考案による低域通過型フイル
タ回路は、楽音信号からその基本波周波数成分を
検出するための前置回路として実用的価値が大き
い。 As described above, the low-pass filter circuit according to the present invention has great practical value as a pre-circuit for detecting the fundamental frequency component of a musical tone signal.
第１図は本考案による低域通過型フイルタ回路
の回路ブロツク図、第２図はVCFのカツトオフ
周波数の変化を説明するための図である。
１……入力端子、２……VCF、３……振幅検
出回路、４……自動制御回路。
FIG. 1 is a circuit block diagram of a low-pass filter circuit according to the present invention, and FIG. 2 is a diagram for explaining changes in the cutoff frequency of a VCF. 1...Input terminal, 2...VCF, 3...Amplitude detection circuit, 4...Automatic control circuit.
Claims (1)
周波数低域通過フイルタと、該低域通過フイルタ
の出力信号を入力して該出力信号の大小に応じた
直流電圧を出力する振幅検出回路と、該直流電圧
を入力してその電圧値の大きさに逆比例した値の
電圧を出力する自動制御回路とを具備し、該自動
制御回路の出力電圧を上記低域通過フイルタの制
御電圧入力端子に引加することによつて、該低域
通過フイルタの出力端子より上記入力楽音信号の
振幅の大小にかかわらず振幅がほぼ一定な出力楽
音信号を得ることを特徴とした低域通過型フイル
タ回路。 A voltage-controlled variable cut-off frequency low-pass filter that receives a musical tone signal as an input; an amplitude detection circuit that receives an output signal of the low-pass filter and outputs a DC voltage according to the magnitude of the output signal; and the DC voltage. and an automatic control circuit that inputs a voltage and outputs a voltage inversely proportional to the magnitude of the voltage value, and applies the output voltage of the automatic control circuit to the control voltage input terminal of the low-pass filter. A low-pass filter circuit characterized in that an output terminal of the low-pass filter obtains an output musical tone signal whose amplitude is substantially constant regardless of the magnitude of the amplitude of the input musical tone signal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3806279U JPS6115625Y2 (en) | 1979-03-23 | 1979-03-23 |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3806279U JPS6115625Y2 (en) | 1979-03-23 | 1979-03-23 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS55138815U JPS55138815U (en) | 1980-10-03 |
| JPS6115625Y2 true JPS6115625Y2 (en) | 1986-05-15 |
Family
ID=28902308
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3806279U Expired JPS6115625Y2 (en) | 1979-03-23 | 1979-03-23 |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6115625Y2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10879760B2 (en) | 2015-06-17 | 2020-12-29 | Mitsubishi Electric Corporation | Permanent-magnet-embedded electric motor for compressor, compressor, and refrigeration cycle device |
-
1979
- 1979-03-23 JP JP3806279U patent/JPS6115625Y2/ja not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS55138815U (en) | 1980-10-03 |
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