JPH07327013A - Vox controlled communication equipment - Google Patents

Abstract

PURPOSE:To attain high quality by avoiding the interruption of speech head in the communication equipment using VOX control. CONSTITUTION:A voice signal converted into a digital signal by a PCM coder 1 is given to a voice coding device 2, in which an average power of a current frame and a reflection coefficient are calculated and they are given to a voice detector 3. The voice detector 3 calculates the change between the average power of a silent block and the average power of a current frame, decides a threshold level based on a threshold level 1 calculated by the average power of the silent block and a weight means of the threshold levels calculated based on a prediction gain decided by 1st-degree to 4th-degree reflection coefficients and discriminates whether a current frame has a voice or silent based on the comparison between the threshold level and the change quantity. Furthermore, the average power of the silent block is sequentially updated by the average power of the current frame and the weight mean discriminated to be a non-voice block.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a VOX control communication control device, and more particularly to a VOX control used in a digital mobile communication device or the like.

[0002]

2. Description of the Related Art Conventionally, VOX (Voice Operated Transistor) has been used as a method for saving power consumption during transmission of radio equipment.
mitter) is known. This VOX is to turn on the power of the transmitter only when an input voice signal is detected and the voice signal is present, and is turned off when the voice signal is not present.
It is a technology.

In particular, in mobile communication devices such as mobile phones, since the power is supplied by a battery, this VOX is widely used as a power saving technique.

In the VOX, if the rising time from the detection of the voice signal to the turning on of the electric power of the transmitter is too long, so-called head disconnection occurs and the voice becomes difficult to hear on the receiving side. Therefore, it is extremely important to detect the presence / absence of a voice signal.

Therefore, in the conventional VOX, whether the voice is present or not is determined by setting a fixed threshold level for the input voice level and comparing these values.

[0006]

However, in the configuration for determining whether there is voice or no voice by using the fixed threshold value as described above, when a low level audio signal such as a consonant is input, However, it may be erroneously determined to be smaller than the fixed threshold, and as a result, there is a problem that the speech is lacking and the sound quality deteriorates.

Therefore, the applicant of the present invention previously filed Japanese Patent Application No. 6-41.
In No. 1, we proposed a configuration in which a threshold value is determined based on the average power in a silent section, and whether it is voiced or silent is determined by comparing it with the variable threshold value. In this way, by determining the threshold value for determining whether there is sound or no sound according to the average power of the silent section, it is possible to reliably detect a low level audio signal even under high noise.

On the other hand, even when the threshold value is determined in accordance with the average power in the silent section as described above, an erroneous determination may occur when a specific consonant (for example, a sa-syaku) comes to the beginning of the talk. , There was a problem that it was not sufficient to prevent the head disconnection for all audio signals.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to reliably prevent the beginning of a talk under high noise and to perform highly efficient VOX control with less malfunction. It is to provide a VOX control communication device.

[0010]

In order to achieve the above object, a VOX control communication apparatus according to claim 1 determines whether a current frame is voiced or silenced when encoding an analog input voice. In a VOX control communication device that transmits only during sound, a change amount calculation unit that calculates a change amount of the average power of the current frame with respect to the average power of a silent section, and a predicted gain based on at least first-order and second-order reflection coefficients Predicting gain calculating means, first threshold calculating means for calculating a first threshold based on the average power of the silent section, and second calculating a second threshold based on the calculated predicted gain. Threshold value calculating means, third threshold value calculating means for calculating a third threshold value by weighted averaging of the first and second threshold values, and comparison of the change amount and the third threshold value. Due to the current And a weighted average of the average power of the silent frame and the average power of the current frame determined to be silent when the current frame is determined to be silent by the determination means. Updating means for updating the average power in the silent section.

Further, in order to achieve the above object, a second aspect is provided.
The described VOX control communication device is characterized in that the predictive gain calculating means calculates the predictive gain based on the reflection coefficients from the first order to the fourth order.

Further, in order to achieve the above-mentioned object, claim 3
In the VOX control communication device described above, the first threshold value calculation means calculates the first threshold value so as to be inversely proportional to the average power of the silent section.

Further, in order to achieve the above object, in the VOX control communication device according to the present invention, the second threshold value calculating means is such that when the predictive gain is R and the positive constant is A,

## EQU1 ## The second threshold value TH is calculated by TH = AR ³ .

[0014]

In the VOX control communication device of the present invention, in order to prevent the lack of consonants when judging whether there is a sound or no sound only by the threshold value calculated based on the average power of the silent section, further based on the reflection coefficient. The final threshold value is determined by weighted averaging with the threshold value based on the calculated prediction gain, and the presence or absence of voice is determined by comparing the threshold value and the amount of change.

When a consonant is input, attention is paid to the fact that the prediction gain calculated based on the reflection coefficient is lowered, and the consonant is determined by determining the threshold value (second threshold value) based on the prediction gain. It can be reliably detected. On the other hand, by determining the threshold value (first threshold value) based on the average power in the silent section, it is possible to cope with a minute power fluctuation even under high noise. Therefore, by determining the final threshold value (third threshold value) by the weighted average of these first threshold value and second threshold value, it is possible to reliably detect consonants even under high noise. Is possible.

The first threshold value is set so as to be inversely proportional to the average power in the silent section, that is, the threshold value is lowered when the noise is high and the average power in the silent section is large, and the second threshold value is set. The value is based on at least the first- and second-order reflection coefficients, and more preferably based on the first- to fourth-order reflection coefficients, and the positive gain is determined based on the predicted gain.
The second threshold value is determined by a cubic function having a degree coefficient. By calculating the predicted gain based on the 1st to 4th order reflection coefficients, it is possible to suppress the threshold value from changing excessively in response to the change in the reflection coefficient, and determine the optimum threshold value in a short time. be able to.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a VOX control communication device of the present invention will be described below with reference to the drawings. FIG. 1 shows a block diagram of the configuration of this embodiment. A voice signal input from a microphone (not shown) is input to the PCM encoder 1 and converted into a digital signal. The digital signal from the PCM encoder 1 is input to the speech encoder 2. The voice encoder 2 calculates the average power and reflection coefficient of the current frame. The calculated average power and reflection coefficient are input to the voice detector 3. The voice detector 3 performs a predetermined calculation and a size comparison described later to determine whether the current frame is voiced or not, and outputs a control signal to the wireless unit 4.
The wireless unit 4 supplies a digital signal to the antenna 5 for transmission when the current frame has a sound based on the control signal from the voice detector 3.

FIG. 2 shows a flowchart of the processing performed by the voice detector 3. As described above, the speech detector 3 receives the average power of the current frame from the speech encoder 2, and the speech detector 3 receives the average power of the inputted current frame and the calculated silent period. The amount of change from the average power is calculated (S101). The average power of the speech encoder 2 is calculated by calculating the sum of squares of the digital signals input from the PCM encoder 1. Further, the average power of the silent section is calculated and sequentially updated based on the average power of the section already determined to be silent, the details of which will be described later. After the change amount of the average power of the current frame with respect to the average power of the silent section is calculated, the voice detector 3
Calculates the prediction gain based on the first to fourth order reflection coefficients input from the speech encoder 2 (S102). Prediction gain R is when the reflection coefficient is ri (i = 1, 2, 3, 4)

[Equation 2] Is calculated by When the prediction gain is calculated using only the first-order reflection coefficient, the prediction gain fluctuates excessively with respect to the fluctuation of the reflection coefficient, which makes it difficult to optimally determine the threshold value. In addition, when the prediction gain is calculated in consideration of the higher-order reflection coefficients of 5th order or higher, the efficiency decreases because the high-order reflection coefficient hardly contributes and it takes a long time to calculate the prediction gain. There is a problem that ends up. Therefore, when calculating the prediction gain,
It is preferable to use the first to fourth order reflection coefficients for the calculation.

After the predicted gain is calculated based on the first to fourth order reflection coefficients, the voice detector 3 determines the threshold value 1 (first threshold value) based on the average power in the silent section (S1).
03). This threshold value 1 is determined so as to be inversely proportional to the average power in the silent section, and in this embodiment, in particular,

## EQU3 ## It is determined by TH1 = -0.0833 (P _O +6). Here, TH1 is the threshold value 1, P _O
Is the average power in the silent section. Note that FIG. 3 shows the relationship between the average power P _{O in the} silent section and the threshold value 1.

Threshold value 1 based on the average power in the silent section
Is determined, the voice detector 3 determines the threshold 2 (second threshold) based on the prediction gain calculated in S102 (S104). The threshold value 2 is determined by a function having a positive correlation such that it decreases as the prediction gain decreases and increases as the prediction gain increases. In the present embodiment, a cubic function is used in particular.

It has been determined by the [number 4] TH2 = 0.0065R ^3.

After the threshold values 1 and 2 are calculated in this manner, the final threshold value (third threshold value) is calculated by weighted averaging of these threshold values (S10).
5). This calculation assumes that each weight is 2: 1

[Equation 5] TH = (2TH1 + TH2) / 3

After the final threshold TH is determined, S
The change amount calculated in 101 and the threshold value TH are compared in size (S106). Then, when the amount of change is equal to or greater than the threshold value, it is determined that the current frame has a sound (S107), and a sound signal is output to the wireless unit 4. on the other hand,
If the amount of change is smaller than the threshold value, a weighted average of the already calculated average power of the silent section and the average power of the current frame is calculated, and the average power of the silent section is updated by this weighted average (S108). ), It is determined that the current frame is silent, and a silent signal is output to the wireless unit 4 (S109).

As described above, in the present embodiment, the voice detector 3 determines whether there is sound or no sound based on the amount of change in the average power of the silent section and the average power of the current frame, and determines the average power of the silent section. Since it is updated sequentially, it is possible to cope with a slight power fluctuation under noise and prevent malfunction. Further, as the threshold value used when determining whether there is voice or silence, it is calculated by a weighted average of the threshold value determined based on the average power of the silent section and the threshold value determined based on the prediction gain. Therefore, it is also excellent in detecting consonants under colored noise, and it is possible to effectively prevent the lack of the talk head and perform high-quality communication.

[0024]

As described above, according to the VOX control communication device of the first to fourth aspects, it is possible to perform highly efficient VOX control with high sound quality and less malfunction.

[Brief description of drawings]

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

FIG. 2 is a processing flowchart in the embodiment of the present invention.

FIG. 3 is a graph showing a relationship between average power in a silent section and a first threshold value in the example of the present invention.

[Explanation of symbols]

 1 PCM encoder 2 voice encoder 3 voice detector 4 radio section 5 antenna

Claims (4)

[Claims] 1. A VOX control communication device for determining whether a current frame has voice or silence when encoding an analog input voice and transmitting only when there is voice, the average power of the current frame with respect to the average power of a silence period. Change amount calculating means for calculating the change amount of the, the predictive gain calculating means for calculating the predictive gain based on at least the primary and secondary reflection coefficients, and the first threshold value based on the average power of the silent section. A first threshold value calculating means; a second threshold value calculating means for calculating a second threshold value based on the calculated prediction gain; and a third weighted average of the first and second threshold values. A third threshold value calculating means for calculating a threshold value; a judging means for judging whether the current frame is voiced or silent by comparing the amount of change and the third threshold value with each other; VOX control comprising: update means for updating the average power of the silent section with a weighted average of the average power of the silent section and the average power of the current frame determined to be silent when it is determined to be sound. Communication device. 2. The VOX control communication device according to claim 1, wherein the predictive gain calculating means calculates the predictive gain based on the reflection coefficients from the first order to the fourth order. 3. The VOX control communication device according to claim 1, wherein the first threshold value calculation means calculates the first threshold value so as to be inversely proportional to the average power of the silent section. A VOX control communication device characterized by the above. 4. Claim 1 or claim 2 or claim 3.
In the VOX control communication device described above, the second threshold value calculation means calculates the second threshold value TH2 by TH2 = AR ³ when the prediction gain is R and a positive constant is A. Characteristic V
OX control communication device.