JPS597399B2 - speech synthesizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a speech synthesis device, and more particularly to a speech synthesis device used in a vocal coder or the like.

FIG. 1 is a schematic block diagram showing an example of a conventional speech analysis device. In this conventional example, audio input from a microphone or the like is input through the input line Ila.
The signal is applied to the formant extraction/sound source extraction circuit 11. This extraction circuit 11 extracts only perceptually necessary information from the audio waveform. For example, formant strength and its frequency are extracted as spectral distribution information from the spectral distribution shown in FIG. Usually, the strength or frequency of such a formant is the first as shown in Figure 2.
Formant, 2nd formant and 3rd formant
Extract about 2 pieces of information. Further, the sound source information includes information for identifying whether the audio input is voiced or unvoiced, pitch period, sound intensity, and the like. These pieces of information extracted by this extraction circuit 11 are then given to an A/D converter 12 as an encoding circuit. This A/D converter 12 converts these extracted pieces of information into digital information. , is applied to the speech synthesis section shown in FIG. FIG. 3 is a schematic block diagram showing a conventional speech synthesizer which is the background of this invention.

The speech synthesizer is provided with an oscillator 21 whose resonant frequency is the pitch period. The signal from this oscillator 21 is used as a sound source by an amplitude control circuit 22 such as an amplifier.
The signal is applied to resonators 23, 24 and 25 through . The resonant frequencies of the resonators 23, 24, and 25 are selected so that they resonate at the frequencies of the extracted first, second, and third formants, respectively. And does the noise generator 26 for the silent state generate white noise? and is applied to the amplitude control circuit 27. The amplitude control circuit 27 controls the amplitude according to the strength.
The voiced or unvoiced identification information extracted by the speech analysis section is
When the sound is a voiced sound, the switch 28 is set to the state shown in FIG. 3, and when the sound is an unvoiced sound, the switch 28 is switched to the state shown in FIG. The signal from this switch 28 drives a speaker 29 through an amplifier (not shown), etc. In such conventional speech synthesizers, the quality of the synthesized speech is not necessarily very good, and the structure is complicated. It was something. Therefore, the main object of this invention is to provide a speech synthesis device that can be constructed easily and inexpensively.Another object of this invention is to provide a speech synthesis device that provides synthesized speech with good quality. That's true.

To summarize, this invention is a method in which a plurality of sine wave signals selected at different frequencies in the audio frequency band are amplitude-modulated in accordance with the sound pressure level to be generated, and the signals are synthesized. , which approximately reproduces the waveform of the spectral distribution. The above objects and other objects and features of this invention will become more apparent from the following detailed description with reference to the drawings.

FIG. 4 is a schematic block diagram showing the Isshiki 1 of the speech analysis section for sending data to the speech synthesis apparatus of the present invention.

Regarding the configuration, the input voice is given to the input line 4a. Then, this audio input is given to, for example, n bandpass filters 411, . . . 41n, and
High pass filter 41. +1 trigram and is applied to the voiced/unvoiced detection circuit 43. Bandpass filter 411,...
41n is for passing frequency components of different bands in the audio band, such as 200 to 5000 Hz, and is provided relatively evenly distributed in the band. Alternatively, the frequencies of these bandpass filters 411, . . . 41n may be selected so as to be concentrated in a specific frequency band. And high bass filter 41. +1 is for extracting unvoiced or noise components of the audio input. The outputs of these filters 411, . . . 41n and 41n+1 are given to corresponding A/D converters 421, . A/D converters 421 to 42n, 42. +1 is digital data 1 to N, n+, respectively, according to the output level of the corresponding filter.
0 to derive 1, this A/D converter 421 to 4
Of course, 2n and 42n+1 may be configured to include a type of peak holding circuit such as a low-pass filter. In addition, the voiced/unvoiced detection circuit 43 is for detecting the voiced state or unvoiced state of the audio input, and determines whether the sound is voiced or unvoiced based on the magnitude, energy, etc. of the autocorrelation function of the audio waveform. To detect.

Another voiced or unvoiced information from this detection circuit 43 is
It is derived as voiced/unvoiced data via the A/D converter 44. FIG. 5 is a schematic block diagram showing one embodiment of the present invention.

In the configuration, an A/D converter 4 included in the voice analysis section 4
21 to 42n, 42. +, and digital data from 44 are given to this speech synthesis section 5. Data 1 to N and n+1 are latched into corresponding latch circuits 511 to 51n and 51n+1, respectively. These data 1 to N, n+1 represent respective frequency bands or levels of noise components, and are converted into analog voltages by D/A converters 521 to 52n, 52n+1. On the other hand, sine wave oscillators 531 to 3n having an oscillation frequency equal to the center frequency of bandpass filters 411 to 41n included in the analyzer 4 are provided.

The outputs of these sine wave oscillators 531 to 53n are given as carrier waves to AM modulators 551 to 55n.
The AM modulators 551 to 55n use the analog signals from the corresponding D/A converters 521 to 52n as modulation signals, and apply amplitude modulation to the input sine wave signals. Also,
A noise generator 54 is provided to generate white noise for unvoiced sounds.

The noise component from this noise generator 54 is given to a gate circuit 56. This gate circuit 56 transmits noise components to the AM modulator 55 when there is no voice based on the voiced/unvoiced data from the A/D converter 44 included in the voice analysis section 4.
Give it to n+1. That is, the circuit for this noise only needs to be activated for unvoiced sounds. Therefore, without providing such a gate circuit 56, it is possible to constantly apply a noise component to the AM modulator 55n+1 and enable or activate the AM modulator 55n+1 only when there is an unvoiced sound. good. The AM modulator 55,+1 applies AM modulation to this noise component using the noise component as a carrier wave and the analog signal from the DA converter 52n+1 as a modulation signal. AM modulator 5 described above
When the outputs of 51 to 55n are voiced sounds, they are sent to the adder 57.
The output of AM modulator 55n+1 is given to adder 57 when it is an unvoiced sound. Then, the adder 57 combines the signals given at that time and supplies the synthesized sum to the amplifier 58. The amplifier 58 drives the speaker 59, and as a result, synthesized audio is generated from the speaker 59. Note that the level changes for each frequency component extracted by the bandpass filter are very gradual (
(at most about 50 Hz), it is sufficient to provide sound pressure level data 1 to N, n+1 every several tens of milliseconds.

Furthermore, it is known that the phase characteristics are of little importance in perceiving speech, and that a moderate phase shift of about 50 msec is not a problem. Not provided. Figure 6 is the 5th
FIG. 3 is a circuit diagram of main parts showing two preferred embodiments of the speech synthesis device shown in the figure.

Although FIG. 6 particularly shows the sine wave oscillator 531, AM modulator 551, and adder 57 in detail, it should be pointed out in advance that other corresponding components can be similarly configured. Sine wave oscillator 531 includes amplifier A1.

One input of the amplifier A1 is connected to a connection point between resistors R1 and R2, and the other input is connected to a connection point between a variable resistor R3 and a capacitor C. The other end of the resistor R1 is grounded, and the other end of the resistor R2 is connected to the output of the amplifier A1. Further, the other end of the variable resistor R3 is grounded, and the other end of the capacitor C is connected to the connection point between the resistor R4 and the thermistor TH. The other end of resistor R4 is amplifier A1
The other end of the thermistor TH is grounded. Regarding such an oscillation circuit, variable resistor R3 and capacitor C determine its oscillation frequency, and resistors R1 and R2 determine its output amplitude. Na, thermistor T
H is for keeping the output amplitude constant. That is, when the amplitude of the oscillation output becomes large, the thermistor TH changes its resistance and functions to suppress the amplitude. The oscillation output from such a sine wave oscillator 531 is given to the AM modulator 551 via a capacitor. The AM modulator 551 has an amplifier A2 which receives the output from the oscillator 531 at one input via a resistor R11. include. The other input of this amplifier A2 is grounded. A parallel circuit including a resistor Rl2 and a light receiving element CdS is connected between one input and the output of the amplifier A2. This light receiving element CdS constitutes a photocoupler PC in cooperation with the light emitting element LED. And the light emitting element LED has D/
The analog voltage from the A converter 521 is applied to the diode D1
and is rectified and smoothed by capacitor C1. Therefore, this light emitting element LED is a compensation converter 521.
The light emission intensity changes depending on the output from, that is, data 1. On the other hand, the light receiving element CdS is such that the more light it receives, the smaller its resistance value becomes. And the gain of amplifier A2 is given by.

Therefore, the gain of this amplifier A2 changes depending on the brightness of the light emitting element LED. In other words, the input to this amplifier A2? The sine wave signal from the sine wave oscillator 531 is AM-modulated by the output of the LE converter 521. Then, the adder 57 receives the output from the similar AM modulator and modulates the sine wave signal from the amplifier 531. Amplifier 58 via A3
Gives the composite output to.

Well, these sine wave oscillators, AM modulators, etc.
It goes without saying that various circuit configurations other than the circuit configuration shown in the figure can be used.

As described above, according to the present invention, the entire apparatus can be constructed from extremely simple components such as an oscillator and an amplitude modulator, so that a cheaper speech synthesis apparatus can be obtained. Also,
The clarity of the synthesized speech is much better than the conventional one.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram showing an example of a conventional speech analysis device. FIG. 2 is a waveform diagram showing an example of spectral distribution. FIG. 3 is a schematic block diagram showing an example of a conventional speech synthesizer which is the background of the present invention. FIG. 4 is a schematic block diagram showing an example of a speech analysis device for providing data to the speech synthesis device of the present invention. No.? 5 is a schematic block diagram showing one embodiment of the present invention. FIG. 6 is a schematic diagram showing the main parts of a preferred embodiment of the embodiment of FIG. 51n, 51n+1 are latch circuits, 521 to 52n, 52n+1 are D/A converters,
531 to 53n are sine wave oscillators, 54 is a noise generator, 551 to 55n, 55n+1 is an AM modulator, 5
7 represents an adder, and 59 represents a speaker.

Claims (1)

[Scope of Claims] 1. A sine wave signal generating means for generating a plurality of sine wave signals each having an oscillation frequency selected to be a different predetermined frequency included in an audio frequency band; A speech synthesis device comprising: a plurality of amplitude modulation means for performing amplitude modulation according to a predetermined intensity; a synthesis means for synthesizing the outputs of the plurality of amplitude modulation means; and a sound generation means for generating sound according to the output from the synthesis means. 2. The amplitude modulation means includes means for providing data on sound pressure levels to be generated by corresponding ones of the plurality of sine wave signals, and analog signal conversion means for converting the sound pressure level data into analog signals, 2. The speech synthesis device according to claim 1, wherein the output of the converting means is used as a modulation signal to amplitude modulate a corresponding sine wave signal. 3. The amplitude modulation means includes a light emitting means that emits light with an intensity corresponding to the analog signal;
3. The speech synthesis device according to claim 2, further comprising a light receiving means optically coupled to the light emitting means, and modulating the amplitude of the corresponding sine wave signal according to the conduction state of the light receiving means. 4. The speech synthesis device according to any one of claims 1 to 3, wherein each of the plurality of sine wave signal generation means is configured to generate a sine wave signal with a constant amplitude.