JP2535808B2 - Sound source waveform generator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus for generating a vocal cord sound source waveform in an apparatus for synthesizing voice and the like.

[Prior Art and its Problems] Conventionally, as a device for synthesizing voices, there is known a device for synthesizing voices by inputting a vocal cord source waveform to a filter that realizes transfer characteristics of the vocal tract.

Conventionally, as a device for generating a periodic vocal cord sound source waveform (hereinafter, referred to as a sound source waveform), a device that generates an impulse train for each pitch period of a voice and an impulse train
It is known that a spectrum generated by a sound source waveform for one pitch is filtered and generated by a filter that approximates the spectrum.
As a conventional example of this, for example, a document "Digital Processing of Speech Signals (Digital Proc
es sing of Speech Signals) ".

However, since the sound source waveform obtained by this conventional example is different from the actual sound source waveform, there is a problem that a synthesized sound with good sound quality cannot always be obtained.

As a second conventional example, it is known that a sound source waveform for one pitch is stored in a memory and the sound source waveform is repeatedly used for each pitch cycle. As an example of the sound source waveform for one pitch in this case, the one given by the following equation is shown in the above-mentioned document.

According to this second conventional example, it is known that a relatively good synthesized sound can be obtained. However, when changing the shape of the sound source waveform, it is necessary to store the respective sound source waveforms, and therefore many There was a problem that it required memory.

Further, if the sound source waveform represented by the equation (1) is to be obtained by calculating the equation (1) at each time, there is a drawback that many calculations are required.

[Object of the Invention]

The object of the present invention is to improve the above-mentioned drawbacks of the conventional ones,
It is an object of the present invention to provide a sound source waveform generation device that can obtain a relatively good synthesized sound by a small number of calculation of a sound source waveform and that can easily change the waveform shape.

[Structure of Invention]

A first aspect of the present invention is a device for generating a periodic sound source waveform of a device for synthesizing a voice or the like, which comprises a pulse generation circuit having variable amplitude, pulse width and pulse generation period, and a cyclic digital filter having variable coefficients. And a non-linear digital filter having means for passing only a non-negative value signal to the output section of the adder, the non-linear digital filter being synchronized with the rising and falling points of the pulse waveform generated by the pulse generating circuit. It is characterized in that the pulse waveform generated by the pulse generating circuit is filtered by the nonlinear digital filter while switching the coefficient of the digital filter.

For the sound source waveform obtained by such a sound source waveform generation device, by further changing the shape of the waveform,
A sound source waveform suitable for synthesizing a desired voice can be generated.

Therefore, according to the second aspect of the present invention, in a device for generating a periodic sound source waveform of a device for synthesizing speech or the like, a pulse generator circuit with variable amplitude, pulse width and pulse generation period, and a cyclic type with variable coefficient A pulse generated by the pulse generation circuit, which is a digital filter, includes a non-linear digital filter having means for passing only a signal having a non-negative value to the output part of the adder, and a linear digital filter having a variable coefficient. While switching the coefficient of the nonlinear digital filter in synchronization with the rising time and the falling time of the waveform,
The pulse waveform generated by the pulse generating circuit is filtered by the nonlinear digital filter, and the output of the nonlinear digital filter is filtered by the linear digital filter.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the first present invention.

This sound source waveform generation device includes a pulse generation circuit 1 whose amplitude, pulse width and pulse generation period are variable, a coefficient variable nonlinear digital filter 2 which filters a pulse from this pulse generation circuit, and a coefficient of this nonlinear digital filter. And a control circuit 4 for controlling the pulse generating circuit 1 and the switch 3.

FIG. 2 is a diagram for explaining an example of the sound source waveform generated by this embodiment. FIG. 2 (a) shows the pulse generated by the pulse generation circuit 1, and FIG. 2 (b) shows the generated pulse. The generated sound source waveform is shown. Although all of them are drawn as continuous signals in time, they are actually discrete signals for each sampling period. The sound source waveform of FIG. 2B is a waveform in which the rising time of the sound source waveform for one pitch is N ₁ and the falling time is N ₂ . N ₁ and N ₂ both represent the number of samples, and the actual time length is N ₁ or N _{2 in the} sampling period.
It is the value multiplied by.

The pulse generation circuit 1 generates the pulse shown in FIG. 2 (a), sends this pulse to the non-linear digital filter 2 through the signal line 5, and at the same time, outputs a synchronization signal indicating the rising time and falling time of the pulse. Switch 3 via line 6
Send to The amplitude, pulse width, and period [see FIG. 2 (a)] of the pulse generated by the pulse generation circuit 1 can be arbitrarily set by the control signal sent from the control circuit 4 through the signal line 7. There is.

The non-linear digital filter 2 is a second-order cyclic digital filter, which includes two delay elements 8 and 9, two multipliers 10 and 11, and an adder 12, and is different from a normal linear digital filter in the adder 12 Means for passing only a non-negative value signal to the output section of (the non-linear element)
It has 13 to make it non-linear. Its non-linear element
The output of 13, that is, the sound source waveform shown in FIG. 2B is output from the signal line 14 as the output of the digital filter 2 and is also fed back to the delay element 8.

The switch 3 selects the signal line 15 and the signal line 16 from the control circuit 4 in synchronization with the synchronization signal sent from the pulse generation circuit 1 through the signal line 6 and outputs the pulse At the time of descending, the signal line 17 and the signal line 18 from the control circuit 4 are selected, and the signal line 15 or the signal line 17 is selected.
From the signal line 19 to the first multiplier 10 inside the nonlinear digital filter 2 and the information from the signal line 16 or the signal line 18 via the signal line 20 to the second inside the nonlinear digital filter 2 To the multiplier 11.

According to the control information input from the signal line 21, the control circuit 4 supplies the pulse generation circuit 1 with the pulse amplitude, pulse width,
It sends the information for controlling the period, and the coefficients a and b of the two multipliers 10 and 11 of the nonlinear digital filter 2 are 2 respectively.
Each value is sent to the switch 3 via the signal lines 15, 16, 17, and 18.

In the sound source waveform generating device having such a configuration, the pulse generating circuit 1 is controlled by the second
A pulse as shown in FIG. When the pulse generation circuit 1 detects the rising time of the pulse, the switch 3
To select the signal lines 15 and 16, and when the pulse falling time is detected, the switch 3 selects the signal lines 17 and 18. The signal lines 15 and 17 have a coefficient a to the first multiplier 10.
However, the coefficient b to the second multiplier 11 is supplied to the signal lines 16 and 18. These coefficients a and b are values determined by the following equations (2) and (3).

(A) Coefficient from the rising edge to the falling edge of the pulse, that is, while the pulse has a non-zero value (B) After the pulse falls, until the next rise, that is, while the pulse is zero In Expressions (2) and (3), N ₁ and N ₂ are the rising time and the falling time of the sound source waveform for one pitch shown in FIG. 2 (b), and in this example, the time N ₁ is the second time. It is set to a value equal to the pulse width of the pulse shown in FIG.

The non-linear digital filter 2 synchronizes with the pulse from the pulse generation circuit 1 and uses the coefficients a and b defined by the equations (2) and (3) as the coefficients of the multipliers 10 and 11, respectively. A sound source waveform as shown in (b) is obtained on the signal line 14. It can be seen that this sound source waveform is a waveform extremely similar to the sound source waveform of the second conventional example shown in equation (1).

According to the present embodiment, the shape of one pitch of the sound source waveform can be freely controlled by controlling only the coefficients a and b determined by the equations (2) and (3) and the amplitude and pulse width of the pulse. Further, by setting the value of R in Expressions (2) and (3) to a value other than 1, the shape of the waveform can be changed in various ways. These points are superior to those of the second conventional example, and the amount of calculation is similar to that of the simplest configuration of the first conventional example.

If the value of R in equations (2) and (3) is fixed to 1, the value of the coefficient b becomes -1 in both cases of equations (2) and (3). The multiplier 11 is unnecessary, and the configuration can be further simplified.

FIG. 3 is a block diagram showing an embodiment of the second invention. In this embodiment, a linear digital filter 22 is provided after the nonlinear digital filter 2 of the embodiment shown in FIG.
Is further added, and the control circuit 23 sends the coefficient value to the linear digital filter 22 via the signal line 24 in accordance with the control information input from the signal line 21. The other structure is the same as that of the embodiment shown in FIG.
The same elements as those in the embodiment of FIG. 1 are designated by the same reference numerals.

According to such a sound source waveform generation device, the linear digital filter 22 filters the output signal of the nonlinear digital filter 2 according to the value of the coefficient sent from the control circuit 23, and outputs the output from the signal line 25 as the sound source waveform. Output.
The frequency characteristic of the linear digital filter 22 is, for example, 6 dB / Oc
If a coefficient is set so as to be a low-pass filter having a cutoff characteristic of t, it is possible to generate a sound source waveform suitable for nasal sounds, for example. As described above, according to this embodiment, by further changing the shape of the waveform obtained by the nonlinear digital filter 2, it is possible to generate a sound source waveform suitable for synthesizing a desired voice.

〔The invention's effect〕

As described above, according to the present invention, it is possible to generate a sound source waveform that can obtain a relatively good synthesized sound with the same amount of calculation as in the first conventional example.

[Brief description of drawings]

FIG. 1 is a block diagram of the first embodiment of the present invention, FIG. 2 is a diagram for explaining a sound source waveform generated by the embodiment of FIG. 1, and FIG. FIG. 2 (b) is a diagram showing an example of the generated sound source waveform, FIG. 3 (b) is a block diagram of the second embodiment of the present invention. 1 …… Pulse generation circuit 2 …… Nonlinear digital filter 3 …… Switch 4,23 …… Control circuit 8,9 …… Delay element 10,11 …… Multiplier 12 …… Adder 13 …… Nonlinear element 22 …… Linear digital filter

Claims (2)

(57) [Claims] 1. A device for generating a periodic sound source waveform of a device for synthesizing speech or the like, comprising a pulse generation circuit having variable amplitude, pulse width and pulse generation period, and a cyclic digital filter having variable coefficients, A non-linear digital filter having means for passing only a non-negative signal at the output section of the adder; and the non-linear digital filter in synchronization with the rising and falling points of the pulse waveform generated by the pulse generating circuit. A sound source waveform generation device, wherein the pulse waveform generated by the pulse generation circuit is filtered by the nonlinear digital filter while switching the coefficient of. 2. A device for generating a periodic sound source waveform of a device for synthesizing voice and the like, comprising a pulse generating circuit having variable amplitude, pulse width and pulse generating period, and a cyclic digital filter having variable coefficient. The output section of the adder comprises a non-linear digital filter having means for passing only non-negative value signals, and a linear digital filter having a variable coefficient, and the rise time and fall of the pulse waveform generated by the pulse generation circuit. The pulse waveform generated by the pulse generation circuit is filtered by the nonlinear digital filter while switching the coefficient of the nonlinear digital filter in synchronism with time, and the output of the nonlinear digital filter is filtered by the linear digital filter. A sound source waveform generation device characterized by the above.