JPH04273621A - Voice communicating system - Google Patents

Abstract

PURPOSE:To keep naturality of talking and high quality in talking by avoiding the production of non-voice period on the halfway of talking and switching the voice/non-voice periods smoothly. CONSTITUTION:When a reception section 22 detects the prediction of transmission stop, a control circuit 30 starts a noise generating circuit 28. After a level is controlled by a level shifter 29 and an adder circuit 25 adds random noise to voice information and the result is sounded from a speaker 27. The voice level is decreased gradually by the level shifter 29, noise is gradually increased and after a reception carrier is interrupted, only noise at a prescribed level is outputted. When the transmission start prediction is detected, the control circuit 30 decreases gradually the gain of the level shifter 29. Random noise is superimposed onto the voice and the result is sounded from the speaker 27. The level of random noise after the lapse of a prescribed time is sufficiently reduced to stop the production and only the voice signal is sounded from the speaker 27. By such constitution, when the voice signal is transited to the voice period, no unnaturality is caused. Even when a speed interruption more or less causes to the transmission voice, random noise is concealed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voice communication device used in a mobile communication system such as a portable/automobile radio telephone system or a cordless radio telephone device.

0002

[Prior Art] Portable voice communication devices such as portable radio telephones and cordless radio telephones generally use batteries as power sources, and miniaturization of these batteries is an important issue in making the devices smaller and lighter. It becomes. In order to downsize batteries, it is of course important to improve the batteries themselves, but it is also important to reduce the power consumption of devices.

[0003]Recently, as a means to reduce the power consumption of the device, a transmitting circuit is operated to transmit the audio signal only during the period when the speaker is speaking during a call, and the voice signal is put on standby between the vocalizations. A method is being considered in which the operation of the transmitter circuit is stopped during the period. If such a system is used, it is possible to reduce power consumption compared to the case where the transmitting circuit is constantly operated during the call period.

0004

[Problem to be Solved by the Invention] However, when such a method is used, a silent section occurs during a call, so the naturalness of the call is lost for the receiver, making it difficult to hear the voice of the other party. There was a problem.

The present invention focuses on the above-mentioned circumstances, and makes it possible to prevent silent sections from occurring during a call, and to smoothly switch between a sound section and a silent section, thereby improving the naturalness of the call. An object of the present invention is to provide a voice communication system that can maintain high quality calls.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention includes means for identifying a sound section and a silent section of an input audio signal, and a means for generating pseudo background noise. In preparation, the input audio signal is output during the sound section, and pseudo background noise is output during the silent section.
Moreover, when switching from a sound section to a silent section, pseudo background noise is superimposed on the input audio signal and output from a predetermined time before the end of the sound section.

[0007] Still another aspect of the present invention includes means for discriminating between a sound section and a silent section of an input audio signal, and a means for generating pseudo background noise. At the same time, a pseudo background noise is output in a silent section, and when switching from a silent section to a sound section, the pseudo background noise is continuously superimposed on the input audio signal until a predetermined period after the start of the sound section. This is how it is output.

Furthermore, the present invention provides a method for superimposing pseudo background noise on an input audio signal during a predetermined period before the end of a sound section.
In the case where the level of the pseudo background noise is controlled to be gradually increased, and when the pseudo background noise is continuously generated until a predetermined period after the start of the sound section and this pseudo background noise is superimposed on the input audio signal, , are also characterized by controlling the level of pseudo background noise to be gradually lowered.

[0009]

[Function] As a result, according to the present invention, pseudo background noise is output during the silent sections of the input audio signal, so there are no silent sections between calls, which makes it easier for the receiving speaker to hear the transmitter's voice. Voice becomes much easier to hear. In addition, when switching from a sound section to a silent section, pseudo background noise is superimposed on the input audio signal from a predetermined time before the end of the sound section before the start of the silent section and is output. Even if there is a difference in timbre between the actual background noise and the pseudo background noise contained in the input audio signal, the switch from sound to silence can be made naturally without making the listener feel uncomfortable. It becomes possible to do so.

On the other hand, according to another aspect of the present invention, when switching from a silent section to a sound section, the pseudo background noise is continuously superimposed on the input audio signal until a predetermined period after the start of the sound section and is output. In this case as well, interruptions in the sound during switching are prevented. Furthermore, even if there is a timbre difference between the actual background noise and the pseudo background noise contained in the input audio signal,
Furthermore, even if the beginning of the voice is cut off due to a delay in detecting the presence of voice on the transmitting side, it is possible to naturally switch from silence to voice without giving the listener a significant sense of discomfort.

Furthermore, in each of the above inventions, by gradually increasing or decreasing the level of the pseudo background noise, switching from sound to silence or from silence to sound can be made more natural. It becomes possible to do so.

0012

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2 are circuit block diagrams showing the configurations of a transmitting system and a receiving system, respectively, of a voice communication device used in a voice communication system according to an embodiment of the present invention.

First, in FIG. 1, the voice transmitted by a speaker is converted into an audio signal by a microphone 11, further digitized by an analog-to-digital (A/D) converter 12, and then input to a wireless transmitter 13. Ru. This wireless transmitter 1
3 includes a digital encoding circuit (CODER) 14 and a transmitting circuit (TX) 15. Digital encoder 1
4 converts the input digitized audio signal into ADPCM (
Adaptive differential pull
The data is compressed and encoded using an encoding method such as (se code modulation). The transmitting circuit 15 modulates a carrier wave with the audio data output from the digital encoding circuit, and transmits the radio carrier signal obtained thereby from the antenna 16 to a radio line.

The digitized audio signal output from the A/D converter 12 is also input to a utterance/silence detector 17 . The utterance/silence detector 17 monitors the signal level of the input digitized audio signal.
The beginning and end of the digitized audio signal are respectively detected. Then, during the period from when the end is detected until when the start is detected, the power supply to the transmitting circuit 15 is cut off to stop the operation of the transmitting circuit 15. Furthermore, when the start end is detected, transmission start information is generated at that point, and this information is supplied to the transmission circuit 15 to be transmitted to the wireless line. Furthermore, when the termination is detected, transmission stop notice information is generated, and this information is supplied to the transmission circuit 15 to be transmitted to the wireless line. Note that detection of the start and end ends of the digitized audio signal can be realized by using a voice detection technique used in voice recognition and voice synthesis techniques.

On the other hand, in FIG. 2, a radio carrier signal sent from a device on the other party's side is received by an antenna 21 and then input to a radio receiving section 22. As shown in FIG. This wireless receiving section 2
2 includes a receiving circuit (RX) 23 and a digital decoding circuit (DECODER) 24. The receiving circuit 23 frequency-converts the received radio carrier signal into a decodable intermediate frequency signal. The received data includes audio data and control data, of which the control data is supplied to the control circuit 30. In contrast, the audio data is supplied to a digital decoding circuit 24. Further, the receiving circuit 23 has a received field strength detector using a carrier squelch or the like, and supplies carrier information detected by this detector to the control circuit 30.

The digital decoding circuit 24 performs a predetermined digital decoding process on the audio data of the intermediate frequency signal output from the receiving circuit 23 to reproduce a digital audio signal. The reproduced digitized audio signal is input to a digital-to-analog (D/A) converter 26 via an adder 25, which will be described later, and is converted back to an analog signal by the D/A converter 26, and then sent to a speaker 27. Amplified sound is output from.

[0017] Furthermore, the receiving system of the voice communication device of this embodiment is as follows:
It includes a noise generation circuit 28 and a level shifter 29. The noise generation circuit 28 includes, for example, an M-sequence random generator, and generates random noise according to instructions from a control circuit 30, which will be described later. This random noise is
It is similar to the ambient noise during a phone call and is used as a pseudo background noise. The level shifter 29 performs calculations under the control of the control circuit 30, variably controls the signal level of the random noise generated from the noise generation circuit 28, and supplies the signal level to the adder 25. The adder 25 adds the random noise supplied from the level shifter 29 to the digitized audio signal output from the digital decoding circuit 24 and outputs the result.

The control circuit 30 is equipped with, for example, a microcomputer as a main control unit, and performs normal control such as control means for selecting and setting a wireless line, connection control means for making/receiving calls and ending calls, etc. In addition to the functions, it has advance notice information detection means 31 and noise output control means 32.

The advance notice information detecting means 31 includes the receiving circuit 2.
Transmission start information and transmission stop notice information are detected from among the control data supplied from 3.

The noise output control means 32 determines the sound interval and the sound period of the received audio signal based on the carrier information supplied from the received field strength detector of the receiving circuit 23 and the detection result of the advance notice information detecting means 31. Identify silent intervals. Then, random noise is generated from the noise generation circuit 28 during a silent period including a certain period immediately before the end of the sound period and a certain period immediately after the start of the sound period, and the level shifter 29 is controlled to increase the level of the random noise. Performs control to change the

Next, the operation of the apparatus configured as above will be explained. In the transmission system, when the speaker has not yet uttered a voice, the utterance/silence detecting section 17 detects that there is a silent section, and as a result, the transmitting circuit 15 is in a transmission halt state. Therefore, the power consumption of the transmitting circuit 15 during this period becomes approximately zero, thereby reducing the power consumption of the wireless transmitter 13. In this case, the power supply to the digital encoding circuit 14 as well as the transmitting circuit 15 may be cut off, thereby stopping the encoding processing operation. In this way, it is possible to further reduce power consumption in the wireless transmitter 13.

Now, when the speaker starts transmission in this state, the utterance/silence detecting section 17 detects the start of transmission, and the transmission circuit 15 becomes ready for transmission. Furthermore, when the start of speech transmission is detected, the utterance/silence detector 17 first generates transmission start information, and this transmission start information is transmitted from the transmission circuit 15 as control data. Immediately after transmitting this transmission start information, the digital code circuit 14
The encoded audio data is input to the transmitting circuit 15,
Transmission of the audio signal is thereby started. Note that the time from when the transmission start information is transmitted until the transmission of audio data is started approximately corresponds to the processing delay time in the A/D converter 12 and the digital code circuit 14.

On the other hand, when the transmission voice is interrupted, transmission stop notice information is generated from the utterance/silence detector 17 at that point, and this information is immediately transmitted before the transmission of the voice data is terminated. Then, when the transmission of the end of the audio data is completed, the power supply to the transmitting circuit 15 is cut off, and the transmitting circuit 15 enters a non-operational state. Thereafter, similarly, the operation control of the transmission circuit 15 and the transmission control of advance notice information are repeatedly performed depending on the presence or absence of the outgoing voice signal.

On the other hand, in the receiving system of the voice communication device communicating with the above-mentioned transmitting system, the following operation is performed. That is, first, during a sound section in which audio data is being received from the other party's audio communication device, the noise generation circuit 28 does not generate random noise. For this reason,
The received audio data is decoded by a digital decoding circuit 24, further converted into an analog signal by an A/D converter 26, and then amplified and outputted from a speaker 27. In other words, only the voice signal of the speaker is output.

In this state, suppose that transmission stop notice information is now detected from the received data. Then, at this point, a start signal is supplied from the control circuit 30 to the noise generation circuit 28, and thereby the noise generation circuit 28 generates random noise. This random noise is level-controlled by a level shifter 29 and then supplied to an adder circuit 25. Therefore, the adding circuit 25 performs processing for adding the random noise to the audio data output from the digital decoding circuit 24. therefore,
Thereafter, the speaker 27 amplifies and outputs the audio signal on which the random noise is superimposed. At this time, the level of the audio signal is controlled to gradually decrease by a level shifter (not shown), while the level of the random noise is controlled to gradually increase by a level shifter 29. Then, when the receiving carrier is cut off after a certain period of time,
Since reception of audio data is stopped, the speaker 27
Only the random noise mentioned above is output. At this time, the level of random noise is fixed to a constant value.

FIG. 3 shows an example of the level transition of the audio signal and random noise (pseudo background noise) in the above operation. As is clear from this figure, random noise is superimposed on the audio signal for a certain period of time before the audio signal is cut off. Therefore, the transition of the audio signal from the sound section to the silent section is performed extremely smoothly without causing any unnaturalness due to interruptions in the sound or differences between the actual background noise and the pseudo background noise.

Next, in this state, when transmission start information arrives from the other party's communication device and is detected by the control circuit 30,
From this point on, the control circuit 30 controls the gain of the level shifter 29 to gradually decrease. Therefore, the level of random noise begins to gradually decrease. Then, when the reception of audio data is started, a signal in which the random noise is superimposed on this audio data is output from the speaker 27, and when the level of the random noise becomes sufficiently small after a certain period of time has passed, the random noise The occurrence of is stopped. Therefore, from now on, only the received audio signal will be output from the speaker 27.

FIG. 4 shows an example of the level transition of the audio signal and pseudo background noise in this operation. As is clear from this figure, even after the reception of audio data is started, a signal with random noise superimposed is output until a certain period of time has elapsed. Therefore, even when the audio signal transitions from a silent section to a sound section, the transition is performed extremely smoothly without any interruption in the sound or any unnaturalness caused by the difference between the actual background noise and the pseudo background noise. Furthermore, even if there is some truncation at the beginning of the transmitted voice on the transmitting side, this can be hidden by the pseudo background noise and made less noticeable.

As described above, according to the present embodiment, random noise is generated in the silent period between the occurrences of calls and outputted from the speaker 27, and moreover, when the silent period is transitioned to a sound period. And when transitioning from a sound section to a silent section, the above random noise is superimposed and output on the start and end parts of the audio signal, respectively, and the level of the random noise at this time is gradually changed. , the receiver can listen to the received voice without feeling too unnatural, thereby improving the quality of the call.

It should be noted that the present invention is not limited to the above embodiments. For example, in the above embodiment, the noise generation circuit 28
In this method, random noise consisting of a digital signal is generated and this random noise is superimposed on the digital audio signal before D/A conversion, but random noise consisting of an analog signal is generated and this noise is superimposed on the digital audio signal before D/A conversion. It may also be superimposed on the audio signal. In this case, a variable gain amplifier or variable attenuator may be used to change the noise level.

Furthermore, in the embodiment described above, the transmitting side sends the transmission stop notice information and the transmission start information, and the receiving side controls the output of the pseudo background noise based on these information. Instead of sending the above information, the receiving side may detect the sound section and the silent section of the received audio signal, and control the output of the pseudo background noise based on the detection results.

Furthermore, in the embodiment described above, pseudo background noise is generated and outputted in the receiving system, but pseudo background noise is generated in the transmitting system, and this noise is applied to the end and start portions of the audio signal. The information may be superimposed and transmitted to the receiving side.

Furthermore, although the above embodiment has been explained by taking as an example a voice communication device employing a digital communication method, the present invention can be similarly applied to a device using an analog communication method.

[0034] In addition, regarding the configuration of the identification means for identifying the sound section and the silent section of the received audio signal, the configuration of the noise generation means, the type of noise, the length of the period in which noise is superimposed on the audio signal, etc. Various modifications can be made without departing from the spirit of the invention.

[0035]

Effects of the Invention As detailed above, according to the present invention, an input audio signal is output during a sound section, and a pseudo background noise is output during a silent section, and from the sound section to the silent section. When switching, pseudo background noise is superimposed on the input audio signal and output from a predetermined time before the end of the sound section, or when switching from a silent section to a sound section, a predetermined period after the start of the sound section. By configuring the system so that pseudo background noise is continuously superimposed and output on the input audio signal until the end of the call, it is possible to prevent silent sections from occurring in the middle of a call, and it is possible to switch between a sound section and a silent section. This makes it possible to provide a voice communication system that maintains the naturalness of calls and allows high-quality calls.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram showing the configuration of a transmission system of a voice communication device according to an embodiment of the present invention.

FIG. 2 is a circuit block diagram showing the configuration of a receiving system of a voice communication device according to an embodiment of the present invention.

FIG. 3 is a diagram showing a transition in signal level when transitioning from a sound period to a silent period in the reception system shown in FIG. 2;

FIG. 4 is a diagram showing a transition in signal level when transitioning from a silent section to a sound section in the receiving system shown in FIG. 2;

[Explanation of symbols]

11...Microphone, 12...A/D converter, 13...Wireless transmitter, 14...Digital code circuit (CODER), 1
5... Transmission circuit (TX), 16, 21... Antenna, 17...
Speech/silence detection section, 22... Wireless receiving section, 23... Receiving circuit (
RX), 24...Digital decoding circuit (DECODER)
, 25... Addition circuit, 26... D/A converter, 27... Speaker, 28... Noise generation circuit, 29... Level shifter, 30
...Control circuit, 31...Advance information detection means, 32...Noise output control means.

Claims (6)

[Claims] 1. A voice communication system that transmits an input voice signal based on pronunciation, comprising: identification means for identifying a sound section and a silent section of the input voice signal; and a noise generation means for generating pseudo background noise. Then, according to the identification result of the identification means, the input audio signal is output in the sound period, the pseudo background noise generated by the noise generation means is output in the silent period, and the input audio signal is output from the sound period. 1. A voice communication system comprising: noise output control means for superimposing pseudo background noise on an input audio signal and outputting it from a predetermined time before the end of a sound period when switching to a silent period. 2. The noise output control means gradually increases the level of the pseudo background noise when superimposing the pseudo background noise on the input audio signal from a predetermined time before the end of the sound section. 1. The voice communication system according to 1. 3. An audio communication system that transmits an input audio signal based on pronunciation, comprising: identification means for identifying a sound section and a silent section of the input audio signal; and a noise generation means for generating pseudo background noise. Then, according to the identification result of the identification means, the input audio signal is outputted in the sound period, the pseudo background noise generated by the noise generation means is outputted in the silent period, and the input audio signal is outputted from the silent period. 1. A voice communication system comprising: noise output control means for continuously superimposing and outputting pseudo background noise on an input received audio signal until a predetermined period after the start of a sound interval when switching to a sound interval. 4. The noise output control means is characterized in that when the pseudo background noise is continuously superimposed on the input audio signal until a predetermined period after the start of the sound period, the level of the pseudo background noise is gradually reduced. The voice communication system according to claim 3. 5. A voice communication system that transmits an input voice signal based on pronunciation, comprising: identification means for identifying a sound section and a silent section of the input voice signal; and a noise generation means for generating pseudo background noise. Then, according to the identification result of the identification means, the input audio signal is output in the sound period, and the pseudo background noise generated by the noise generation means is output in the silent period, and the sound period is changed to the silent period. When switching to a sound section, pseudo background noise is superimposed on the input audio signal from a predetermined time before the end of the sound section, and when switching from a silent section to a sound section, the received audio signal is superimposed and output for a predetermined period after the start of the sound section. A voice communication system comprising noise output control means for continuously superimposing pseudo background noise on and outputting the same. 6. In a voice communication system that transmits an input audio signal based on pronunciation from a transmitting device to a receiving device, the transmitting device includes a first audio signal for identifying a sound section and a silent section of the input audio signal. The receiving device includes an identification means and a transmission stop means for stopping the transmission operation during the transmission period corresponding to the silent period detected by the first identification means, and the receiving side device distinguishes between the sound period and the silent period of the received audio signal. a second identifying means for identifying, a noise generating means for generating pseudo background noise, and outputting the received audio signal in a sound interval according to the identification result of the second identifying means; The pseudo background noise generated by the noise generating means is outputted in the silent section, and when switching from the sound section to the silent section, the pseudo background noise is superimposed on the input audio signal from a predetermined time before the end of the sound section. and a noise output control means that continuously superimposes and outputs pseudo background noise on the received audio signal until a predetermined period after the start of the sound period when switching from a silent period to a sound period. voice communication system.