JPH04301896A - Muting device - Google Patents

Abstract

PURPOSE:To prevent the quantization noise for reduction of the sound volume level of a musical sound signal from being conspicuous and to perform effective muting based on the property of the musical sound signal. CONSTITUTION:A level setting mean 1 which sets the muting level for muting of the musical sound signal based on the property of the musical sound signal with respect to the envelope level of the musical sound signal, a level detecting means 2 which detects the shift of the envelope level of the musical sound signal to the muting level set by the level setting means 1 or lower, and a muting means 3 which erases the musical sound signal based on detection of the shift of the envelope level to the prescribed level or lower in the level detecting means 2 are provided.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a muting device, and more specifically, the present invention relates to a muting device, and more specifically, the present invention relates to a muting device that suppresses quantization noise that becomes noticeable when the envelope level of a musical tone signal becomes small, or in other words, when the volume level becomes small. It concerns muting technology that makes it less noticeable.

0002

2. Description of the Related Art In recent years, it has become common practice to convert musical tone signals into digital signals, in other words, to approximate the waveform of musical tone signals to a stepped waveform and process them in a quantized digital format.

0003

[Problems to be Solved by the Invention] However, when processing musical tone signals in digital format, when the envelope level becomes small and the volume level of the musical tone signal becomes small, the S/N ratio cannot be maintained sufficiently, and quantum There is a problem that noise becomes noticeable.

In order to solve these problems, the present invention makes the quantization noise less noticeable when the volume level of the musical tone signal becomes small, and also makes the quantization noise less noticeable based on the characteristics of the musical tone signal. The present invention aims to provide a muting device capable of muting.

[0005]

[Means for Solving the Problems] In order to achieve the above-mentioned object, a muting device according to the present invention is provided as shown in FIG.
A) As shown in the principle block diagram of the principle configuration, (a) level setting means 1 for setting a muting level for muting a musical tone signal based on the characteristics of the musical tone signal with respect to the envelope level of the musical tone signal; (b)
Level detection means 2 detects that the envelope level of the musical tone signal shifts below the muting level set by this level setting means 1; and (c) Based on the detection by this level detection means 2 that the envelope level is below a predetermined level. This apparatus is characterized by comprising a muffling means 3 for muffling the musical tone signal. or Figure 1 (
B) As shown in the principle block diagram of the principle configuration, (a) level detection means 6 for detecting the envelope level of the musical tone signal, (b) the envelope level of the musical tone signal detected by this level detection means 6. level changing means 7, (
c) level detection means 8 for detecting when the envelope level of the musical tone signal changed by this level change means 7 shifts below a predetermined level; It is originally characterized by comprising a muffling means 9 for muffling the musical tone signal.

[0006]

[Operation] Level setting means 1 based on the characteristics of the musical tone signal
A muting level for muting the musical tone signal is set, and when the level detection means 2 detects that the envelope level of the musical tone signal shifts below the set muting level, based on this detection, the muting level is set by the muting means 3. The musical tone signal is muted.

Alternatively, the envelope level of the musical tone signal is detected by the level detecting means 6, and the envelope level of the detected musical tone signal is changed by the level changing means 7 based on the characteristics of the musical tone signal. When the level detecting means 8 detects that the envelope level of the changed musical tone signal goes below a predetermined level, the muting means 9 mutes the musical tone signal based on this detection.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, specific embodiments of the muting device according to the present invention will be described with reference to the drawings.

First, in FIG. 2 showing a schematic diagram of an electronic musical instrument, each key is pressed or released on a keyboard 15 consisting of a plurality of keys for specifying the pitch of a musical tone to be sounded. The control unit 1 comprising a microcomputer or the like determines which key is operated based on the key operation, and whether the key is pressed or released.
6. In addition, the control unit 16 similarly detects the operation state of each tone color selection switch, etc. with respect to the operator group 17, which includes tone color selection switches and the like for selecting tones of piano, harpsichord, etc., for example. Note that the muting level memory 18 from which necessary data can be read under the control of the control unit 16 stores muting level data used during muting processing for each tone range of the key operated on the keyboard 15. , are stored in association with each tone color selection switch operated by the switch of the operator group 17.

By the way, in the control section 16, based on the key operation state of each key and the switch operation state of each tone selection switch etc. detected by the control section 16, pitch, tone, and envelope are sent to the musical tone signal generation circuit 19. This musical tone signal generation circuit 19
to generate the desired musical tone. This musical tone signal generation circuit 19
When the control section 16 detects a new key press, the control section 16 generates a plurality of musical tone signal generation channels from among, for example, 30 musical tone signal generation channels constituting the musical tone signal generation circuit 19. In this embodiment, two musical tone signal generation channels are selected based on a predetermined priority order, and the control unit 1 selects these selected musical tone signal generation channels.
6 to a pitch control signal corresponding to the pressed key;
Further, this is done by providing a timbre control signal and an envelope shape control signal corresponding to the timbre selected by the timbre selection switch, as well as an envelope start signal for starting the generation of the envelope signal. These 2
The timbre control signals given to each musical tone signal generation channel are different from each other, and the envelope shape control signals are also set to values that are slightly different from each other, although the changes in the envelope level over time are almost the same. There is. The musical tone obtained in this manner is a mixture of two musical tone signals. On the other hand, when the control unit 16 detects a new key release, the control unit 16 selects two musical tone signal generation channels that are currently generating musical tones corresponding to the released key, and selects these two musical tone signal generation channels. This is done by applying an envelope end signal from the control section 16 to the selected musical tone signal generation channel to instruct the end of envelope signal generation.

The musical tone signal generated as described above is
After being converted into an analog signal by the D/A converter 20, it is amplified by the amplifier 21 and emitted as a musical tone from the speaker 22.

Next, one of the 30 musical tone signal generation channels making up the musical tone signal generation circuit 19 will be explained based on FIG. The address signal generation circuit 25, which is given frequency data as a pitch control signal corresponding to the pitch of the pressed key from the control section 16, sequentially generates the address signal by accumulating this frequency data. Generate. This sequentially generated address signal is applied to a waveform memory 26 in which a plurality of musical sound waveforms corresponding to each tone selected by each tone selection switch of the operator group 17 are stored as amplitude values for each address. From the waveform memory 26, the amplitude values of musical waveforms of the timbre selected by the timbre selection switch and designated via the control section 16 are sequentially read out based on the address signal. The amplitude values of the musical waveforms read out sequentially in this way are given to the multiplier 27, and the multiplier 27 receives an envelope signal based on the envelope shape control signal given from the control section 16 based on the timbre selected by the timbre selection switch. The envelope signal is given from the envelope signal generation circuit 28 that generates it. Therefore, in the multiplier 27, the amplitude values sequentially read out from the waveform memory 26 and the envelope signal generation circuit 2
8, and a signal whose volume is controlled by the envelope signal is output as a musical tone signal.

Incidentally, the generation of the envelope signal is started by the envelope start signal given from the control section 16, and the generation of the envelope signal is similarly terminated by the control section 16.
The generated envelope signal is also provided to the control section 16 in addition to the multiplier 27. Note that a typical waveform shape of the envelope signal generated in the envelope signal generation circuit 28 is shown in FIG. Correspondingly, the level attenuation speed and the like of the envelope signal are made different.

Next, muting processing will be explained. This muting process is performed by the control unit 16 at predetermined time intervals, for example, at 10 m se
This is accomplished by performing processing every c. The muting level corresponding to the pitch of the musical tone being generated in the musical tone signal generation channel in which the envelope signal is in an attenuated state, in other words, the range of the key for the musical tone being generated, and the currently selected tone selection switch. , read from the muting level memory 18. Next, this read muting level is compared with the envelope signal level of the musical tone signal generation channel,
When this envelope signal level becomes lower than the read muting level, another musical tone signal generation channel that is currently generating a musical tone is searched for in response to the same key press as that of the musical tone signal generation channel, and both musical tone signal generation channels are "0" is given as frequency data to each address signal generation circuit 25 in the signal generation channel. This address signal generation circuit 25 is
Because it accumulates given frequency data,
When "0" is given as frequency data, an address signal of the same value is repeatedly generated as an address signal. Therefore, the amplitude values of the same value are repeatedly read out from each waveform memory 26 of both musical tone signal generation channels by the address signals of the same value, and the generated first and second musical tone signals are simply It becomes a direct current component and is outside the audible range, so it becomes inaudible as a sound and quantization noise also disappears.

In short, any one of the two musical tone signals generated in response to a sound generation instruction based on the same key press.
When the envelope signal level of each musical tone signal moves below the muting level, all musical tone signals caused by generation instructions based on the same key depression are muted.

The muting level data stored in the muting level memory 18 is, for example, a value approximately 70 decibels lower than the maximum level of the envelope signal level, and is selected again as the sound range becomes higher. The value is set to increase as the attenuation speed of the envelope signal level generated corresponding to the timbre decreases. For example, the muting level corresponding to a tone whose envelope signal level decay rate is a standard value is set to be 70 decibels lower than the maximum level in the center range, and the range is one octave below this value. 2 as it gets higher each time
The value increases in decibel increments, and decreases in 2 decibel increments as the range gets lower by one octave. Furthermore, the muting level corresponding to a tone whose envelope signal level decay rate is half the standard rate is a value 65 dB lower than the maximum level in the center range, and the change in the tone range with respect to this value is It is set up the same way. Furthermore, the muting level corresponding to a tone in which the envelope signal level decay rate is twice the standard rate is set to a value 75 decibels lower than the maximum level in the center range, and the changes in the range with respect to this value are as described above. The settings are the same as the tone ones. The reason for this is that quantization noise tends to be more noticeable the higher the range of the musical tone being generated and the slower the attenuation rate of the envelope signal level. This is to set the level. By setting in this manner, muting is performed that is appropriate for the characteristics of each musical tone. In addition, since muting processing is performed simultaneously on the two first and second musical tone signals generated in response to instructions for sound generation based on the same key depression, each musical tone as described below The unnaturalness that occurs when muting processing is performed at separate timings for each signal does not occur.

As shown in FIG. 5, the envelope signal levels of the first and second musical tone signals generated in response to instructions for producing sound based on the same key depression both exceed the muting level. In this case, the desired tone is synthesized. However, although the first musical tone signal is muted at point A when its envelope signal level falls below the muting level, the second musical tone signal is not muted yet, so the synthesized tone may not be the desired one. On the other hand, the timbre changes rapidly, resulting in an unnatural musical sound.

Note that even if the same amplitude value is repeatedly read out from the waveform memory 26 using the same address signal, the finally obtained musical tone signal is added to the amplitude value read out from the waveform memory 26 by a multiplier. 27 by the envelope signal from the envelope signal generation circuit 28. Therefore, the amplitude value after multiplication changes over time as the envelope signal level of the envelope signal changes, even if the same amplitude value is read out repeatedly from the waveform memory 26, for example. The sound generated by this is almost never unpleasant to the ears. However, if this sound is harsh,
At the same time as giving "0" as frequency data to the waveform memory 26, the envelope signal generation circuit 28 is controlled so as to keep the envelope signal level of the envelope signal constant, so that the amplitude value of the musical tone signal output from the multiplier 27 is completely It is also good to have a constant value. In addition, in this embodiment, the frequency data is set to "0" when the envelope signal level becomes equal to or lower than the muting level. It is also good to set it to a value other than "0".

In this embodiment, the muting level is changed based on the characteristics of the musical tone in order to detect the transition of the envelope signal level to a predetermined level or lower, in other words, to detect that the envelope signal level is lower than the muting level. However, the same effect can be obtained even if the muting level is kept constant and the envelope signal level of the envelope signal obtained from the envelope signal generation circuit 28 is changed based on the characteristics of the musical tone and then compared with the muting level. Needless to say. For example, when the pitch of the musical tone being generated is high, the envelope signal level of the envelope signal obtained from the envelope signal generation circuit 28 is changed to be small, and when the pitch of the musical tone being generated is low, the envelope signal level of the envelope signal obtained from the envelope signal generation circuit 28 is changed. After changing the envelope signal level of the signal to increase it, it is compared with the muting level.

In this embodiment, when determining whether or not to mute a musical tone signal, the range of the musical tone and the attenuation speed of the envelope signal level are taken into consideration as characteristics of the musical tone. It is not limited to these sound ranges and attenuation speeds. For example, other factors may be taken into consideration, such as the brightness of the timbre and whether the musical tone has a constant period or is aperiodic noise-like. Furthermore, when controlling the characteristics of musical tones according to factors such as key pressing speed, it is good to mute directly based on the characteristics of the musical tones, but It is also a good idea to perform muting based on the factors.

In this embodiment, the envelope level of the envelope signal generated in the envelope signal generating circuit 28 is used to obtain the envelope level of the musical tone signal being generated. It is also good to place it on the side and obtain it with this envelope level detector.

In this embodiment, the musical tone signal obtained when the envelope level falls below the muting level contains a DC component, but since the level of this DC component is very low, there is usually no problem. It is not. If this DC component becomes a problem, a high-pass filter or the like that removes the DC component may be placed on the output side. Alternatively, if the muting process is performed at the first zero-crossing point of the amplitude value of the musical tone signal after the envelope level of the musical tone signal becomes less than the muting level, no DC component is generated.

In this embodiment, muting is performed by controlling the pitch of the musical tone signal, but it is also possible to rapidly attenuate the volume level of the musical tone signal or to rapidly attenuate the high frequency components of the musical tone signal. It is also good to perform muting using methods such as the following. Furthermore, when rapidly attenuating the volume level of a musical tone signal, for example, a separate multiplier may be provided on the output side of the multiplier 27 of each musical tone generation channel, and the coefficients of this multiplier may be changed to reduce the output musical tone signal. It is also good to control the amplitude value. Alternatively, from the envelope signal generation circuit 28 to the multiplier 27
It is also a good idea to rapidly attenuate the envelope signal applied to the signal. In order to attenuate the high-frequency components of the musical tone signal, a dedicated low-pass filter is provided for each musical tone generation channel, for example, on the output side of the multiplier 27 of each musical tone generation channel, and the cutoff frequency of this low-pass filter is set. It is also a good idea to lower it rapidly. or
When a low-pass filter for timbre processing is provided between the waveform memory 26 and the multiplier 27, it is also good to sharply lower the cutoff frequency of this low-pass filter.

[0024]

As explained above, according to the present invention, when the envelope level of the musical tone signal becomes small, the volume level of the musical tone signal becomes small, and quantization noise becomes noticeable, the musical tone signal becomes The sound is muted and cannot be heard as sound, and the quantization noise is also reduced, making it less noticeable. Furthermore, in this case, the timing at which the musical tone signal is muted is varied based on the characteristics of the musical tone signal, thereby achieving effective muting.

[Brief explanation of drawings]

FIG. 1 is a principle block diagram for explaining the principle configuration of a muting device according to the present invention.

FIG. 2 is a schematic block diagram of a specific embodiment of a muting device according to the present invention.

FIG. 3 is a block circuit diagram of the musical tone signal generation channel explained in FIG. 2;

FIG. 4 is a waveform diagram of a typical envelope signal generated as described in FIG. 3;

FIG. 5 is an explanatory diagram showing temporal changes in envelope signals of first and second musical tone signals generated in response to a sound generation instruction based on the same key depression described in FIG. 3;

[Explanation of symbols]

1 Level setting means 2, 8 Level detecting means 3, 9 Silencing means 6 Level detecting means 7 Level changing means 15 Keyboard 16 Control section 17 Operator group 18 Muting level memory 19
Musical tone signal generation circuit 20 D/A converter 21 Amplifier 22 Speaker 25 Address signal generation circuit 26
Waveform memory 27 Multiplier

Claims (2)

[Claims] 1. (a) Level setting means for setting a muting level for muting a musical tone signal based on the characteristics of the musical tone signal with respect to the envelope level of the musical tone signal; (b) Muting set by the level setting means. a level detection means for detecting that the envelope level of the musical tone signal shifts below the level; and (c)
A muting device characterized by comprising a muting means for muting the musical tone signal based on detection of an envelope level below a predetermined level by the level detecting means. 2. (a) Level detection means for detecting the envelope level of a musical tone signal; (b) Level changing means for changing the envelope level of the musical tone signal detected by the level detection means based on the characteristics of the musical tone signal. , (c) level detection means for detecting that the envelope level of the musical tone signal changed by the level changing means shifts below a predetermined level; and (d) based on the detection of the envelope level being below a predetermined level by the level detection means. A muting device comprising a muting means for muting the musical tone signal.