JPH0462594A - Sound quality improving device for pitch changer - Google Patents

Abstract

PURPOSE:To obtain excellent sound quality whose high frequency range is expanded without inhibiting the passage of the high frequency range by providing a pitch changer circuit which varies an interval in an acoustic circuit and also providing a filter which is variable in passing frequency with an operation signal applied thereto. CONSTITUTION:When a signal is sent to the pitch changer circuit 5, the signal is sent to low-pass filters 2 and 7 from a CPU 9 by signal lines 12 and 13, so the filters 2 and 7 vary in cutoff frequency according to the kind of the signal, i.e., whether the circuit 5 increases or decreases the pitch. The cutoff frequencies of the filters 2 and 7 increase as the circuit 5 increases the pitch, so when the pitch is increased only by one or two, the frequency range is not cut off by the filters 2 and 7 although the frequency range is expanded up to about 15KHz, thereby obtaining superior sound quality in the high frequency range.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a pitch changer sound quality improvement device that can be implemented in electronic musical instruments, karaoke devices, and the like.

(Prior art) Since electronic musical instruments use electrical oscillators to create musical scales, electrical signals (
audio signal). Since it is an electrical signal, various electrical processing is possible. Pitch changer is one of them.
In the process of guiding the audio signal to a digital circuit and digitally processing it, the pitch is converted by expanding or compressing it in the time axis direction.

FIG. 3 shows a conventional acoustic circuit equipped with a pitch changer circuit. In this circuit, l is an input side terminal, which receives an audio signal of an appropriate voltage level. To this input terminal l, an amplified oscillator output is connected in the case of an electronic musical instrument, and a low frequency amplification circuit is connected in the case of a karaoke apparatus. A low-pass filter 2 whose cut-off frequency is fixed to a cut-off frequency set by the amount of pitch shift or reproduction frequency is connected to the input side 1, and the output side of this low-pass filter 2 has a sampling frequency of 44 An A/D conversion circuit 4 is connected via a sampling halt circuit 3 with a frequency of .1 KHz. As is well known, the sampling halt circuit 3 reads and stores the input analog voltage at that time in response to an external command, and the A/D converter circuit 4 converts the output voltage from the analog signal into a digital signal. It is.

A pitch changer circuit 5 is connected to the output side of the A/D conversion circuit 4, and a low pass filter 7 is connected to the output side of the pitch changer circuit 5 via a D/A conversion circuit 6. This low-pass filter 7 also has the same characteristics as the low-pass filter 2 at the input stage.
The cutoff frequency is set to the aforementioned cutoff frequency. An output terminal 8 is connected to the output side of the low-pass filter, and is connected to an output amplification circuit. A CPU (central processing circuit) 9 is connected to the pitch changer circuit 5, and a key bat 10 for giving commands to the pitch changer circuit 5 and a display II for displaying the status of the pitch changer circuit 5 are connected.

In a conventional acoustic circuit having such a configuration, when a low-frequency signal is applied from the input side I, this signal passes through the low-pass filter 2 to cut off the high-frequency components, and in this state, the sampling hole Human power is applied to circuit 3. After being sampled and held here, A
The signal is converted into a digital signal by the /D converter 4 and input to the pitch changer circuit 5. Pitch changer circuit 5
When receiving a command from the key bat IO side via the CPU 9, it performs a pitch changer action through digital signal processing, and outputs the resulting signal to the D/A converter 6. At the same time, the signal is sent to the display 11 via the CPU 9 to display that the pitch has been changed. D/
The analog signal that has passed through the A converter 6 is outputted to an output terminal 8 via a low-pass filter 7, and is directed from a low frequency amplifier (not shown) to a speaker.

(Problems to be Solved by the Invention) In the conventional acoustic circuit described above, for example, considering the case of l-octave pitch shift, the cutoff of the low-pass filter 2 provided on the input side and the low-pass filter 7 provided on the output side The reason why the frequency was set to about 10 KHz is that the sampling frequency was set to 44.1 KHz and the upper limit frequency of the audible band was set to 20 KHz. In this way, low pass filters 2 and 7
If the cutoff frequency of 5 is raised by 1 octave by setting the cutoff frequency to approximately 10KHz, the output signal will be 20KH.
z, so no problem arises in terms of signal reproducibility. And suppose the input signal is 5KHz per month.
Even if you raise this by one octave, it will not become 30KHz due to the sampling theorem, so there is no problem in this case.8 The problem is that the frequency band changes depending on how the pitch is raised. That's true. The change in frequency band will be extended by a factor of 1212 for every half FZ [100 cents].

In this way, every time you raise the pitch by a semitone, the band increases by 12J2 times,
Due to this extension, the rising high frequency is cut by the low pass filter 2.7, especially the low pass filter 9 on the output side, resulting in a lack of high frequencies. Specifically, the pitch is
When raising only a note (200 cents) or two notes (400 cents), the frequency band can be extended to about 15 KHz, but the frequency band is limited by the low-pass filter 2.7 connected to the input and output sides. It becomes restricted.

The present invention has been made in view of the above-mentioned problems of the conventional circuit, and an object of the present invention is to provide a circuit that changes the cutoff frequency of a low-pass filter in accordance with a pitch shift.

(Means for Solving the Problems) The present invention provides a first method for solving the problems described above.
As shown in the figure or Figure 2, the analog waveform audio signal is A/D converted (A/D converter 3), and after digital processing, it is D/A converted (D/A converter) to produce an analog audio signal. In the acoustic circuit to be reproduced, a pitch changer circuit 5 for changing the pitch is provided in the acoustic circuit, and a filter (low-pass filter 2. 7 or a digital filter +5) functioning as a low-pass filter.

(Function) With this configuration, when an operation signal is applied to the pitch changer circuit 5 using the key bat 10 or the like to change the pitch, the cutoff frequency of the low-pass filter 2.7 or the limit frequency of the digital filter 15 changes at the same time. Since the passing frequency changes, the high frequency range is not blocked from passing as in the conventional system, and good sound quality with an extended high frequency range can be obtained.

(Example) Next, FIG. 1, which is a first example of the present invention, will be described. In FIG. 1, reference numeral 1 denotes an input side terminal, which receives an audio signal of an appropriate voltage level.

A low-pass filter 2 whose cutoff frequency can be changed is connected to this input side element 1. The output side of low-pass filter 2 has a sampling frequency of 44
．． An A/D converter 4 is connected via a sampling halt circuit 3 with a frequency of 1 KHz.

A pitch changer circuit 5 is connected to the output side of the A/D converter 4, and a low-pass filter 7 is connected to the output side of the A/D converter 4 via a D/A converter 6. Similar to the low-pass filter 2 at the input stage of this low-pass filter 76, it has a structure in which the cutoff frequency can be changed. An output terminal 8 is connected to the output side of the low-pass filter 7, and is connected to an output amplification circuit. A CPU (central processing circuit) 9 is connected to the pitch changer circuit 5, and a key bat lO for giving commands to the pitch changer circuit 5 and a display 11 for displaying the status of the pitch changer circuit 5 are connected. A feature of the present invention is that signal lines 12 and 13 are provided for sending signals from the CPU 9 to the low-pass filter 2 of the human power filter 1 and the low-pass filter on the output side.

Similarly to the circuit of the present invention having such a configuration, when a low frequency signal is applied from the input terminal 1, this signal passes through the low pass filter 2, so that high frequency components are removed. The signal is cut and input to the sampling halt circuit 3 in that state. After being sampled and held here, the signal is converted into a digital signal by the A/D converter 4 and input to the pitch changer circuit 5. The pitch changer circuit 5 connects the CPU 9 from the key bat 10 side.
When a command is received via the digital signal processing, a pitch changer effect is performed, and the resulting signal is output to the A/A converter 6. At the same time, the signal is sent to the display 11 via the CPU 9 to display that the pitch has been changed. The analog signal that has passed through the D/A converter 6 is outputted to an output terminal 8 via a low-pass filter 7, and is directed from a low-frequency amplifier (not shown) to a speaker.

In this case, when the CPU 9 sends a signal to the pitch changer circuit 5, the signal is also sent to the low-pass filters 2.7 via the signal line 1213, so these low-pass filters 2.7 can be configured to The cutoff frequency is changed depending on whether the pitch changer circuit 5 raises or lowers the pitch. Now, if we want to raise the # (natural) pitch, we will lower the cutoff frequency below the upper audible frequency of 20 KHz. The amount of change is approximately 18KHz when raised by a semitone (100 cents), and approximately 17 when raised by one tone (200 cents).
When the frequency is 1.5 KHz, the frequency is about 16 KHz.

In this way, in the pitch changer sound quality improvement device of the present invention, the cutoff frequency of the low-pass filter 2.7 increases as the pitch of the pitch changer circuit 5 increases, so the pitch can be raised by only one or two tones. Even though the frequency band can be extended to about 15KHz when there is no signal, it will not be cut off by the low-pass filter 2.7 like the one in Figure 3, and the high-frequency sound quality will be excellent. You will be able to get it.

What is shown in FIG. 2 is a second embodiment of the invention. In this example, the cutoff frequency of the low-pass filter 2.7 is 20K, which is twice the frequency of the one in FIG.
Hz and has a built-in pitch changer circuit 5 and digital filter 15 after the A/D converter 4.
S P (Digital Signal Processes
ser), and the band frequency is limited by a digital filter 15 provided inside the filter.

In this case, the key change command is also from keypad IO to C.
1 and 2 in that it is carried out via PU9.
There is no difference from the one in the picture.

(Effects of the Invention) As described above, the present invention provides an acoustic circuit that A/D converts an analog waveform audio signal, performs digital processing, and then D/A converts it to reproduce an analog audio signal. A pitch changer circuit for changing the pitch is provided in the acoustic circuit, and a filter is provided in the acoustic circuit, the passing frequency of which can be changed by an operation signal applied to the pitch changer circuit. As for its specific configuration, on the input side and output side of the acoustic circuit,
a low-pass filter whose passing frequency can be changed by an operation signal applied to the pitch changer circuit;
Alternatively, a digital filter functioning as a low-pass filter is provided within the pitch changer component, the pass frequency of which can be varied by an operating signal applied to the pitch changer. Therefore, when changing the pitch of the pitch changer circuit by operating a key butt, etc., the high range is limited by the low-pass filter in the circuit and is cut, and the high range reproduction is not impaired, so the sound quality in the high range is improved. There are benefits that could be improved.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a first embodiment of the present invention, FIG. 2 is a circuit diagram of a second embodiment of the present invention, and FIG. 3 is a circuit diagram showing a conventional pitch changer circuit. 27...Low pass filter 3 - Sampling halt circuit 4 - A/D converter 5 - Pitch changer circuit 6 - D/A converter 12, 13 - Signal line 4 - DSP 15 - Digital filter patent Patent Applicant: Japan Pressure Denki Co., Ltd.

Claims (2)

[Claims] (1) In an acoustic circuit that A/D converts an analog waveform audio signal, performs digital processing, and then D/A converts it to reproduce the analog audio signal, a pitch changer circuit that changes the pitch is provided in the audio circuit, and A sound quality improvement device for a pitch changer, characterized in that a low-pass filter whose passing frequency can be changed by an operation signal applied to the pitch changer circuit is provided on the input side and the output side of the acoustic circuit. (2) In an acoustic circuit that A/D converts an analog waveform audio signal, performs digital processing, and then D/A converts it to reproduce the analog audio signal, a pitch changer circuit that changes the pitch is provided in the audio circuit, and A sound quality improvement device for a pitch changer, characterized in that a low-pass filter is provided in a component of the pitch changer circuit to limit a passing frequency according to an operation signal applied to the pitch changer circuit.