JP3061002B2 - Background noise generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a background noise generator, and more particularly to a background noise generator suitable for use in a PHS (Personal Handy Phone System) having a VOX function, a portable telephone, or the like.

[0002]

2. Description of the Related Art In digital mobile communication, VOX (Voice Operated Tran) is used today.
Many mobile stations have a (smitter) function. The VOX is a function of a mobile station during communication turning on / off a transmission output according to the presence or absence of voice, and is a function performed to reduce power consumption of the mobile station. When there is no voice, especially in a digital type mobile station, there is no sound and it is easy to be illusioned that the line is disconnected. For this reason, background noise is generated by itself, and the user is made aware of the connection with the communication partner.

FIG. 2 shows an example of the configuration of a conventional background noise generator. As shown in FIG. 2, a sound / non-speech determination circuit 2-3 for determining whether the reception signal 2-1 is sound or non-sound, and a signal level detection circuit 2 for detecting the power level of the reception signal at the background noise level update timing. -4, and a background noise generating circuit 2-5 that generates background noise on the receiving side according to the signal level. When the received signal is a sound, the received signal is output as it is, and no sound is generated. In some cases, the background noise was output from the multiplexer 2-2 at a level proportional to the signal level at the timing of updating the background noise level.

FIG. 3 shows the configuration of a PHS (Personal Handy Phone System) terminal with a VOX noise determination function, which is a mobile station terminal in a digital cordless telephone system described as a prior art in Japanese Patent Application Laid-Open No. 8-79163. Show.

Referring to FIG. 3, a PHS terminal includes a transmitter 3-1, an amplifier 3-2, and a PCM encoder 3-3.
And ADPCM (Adaptive Differen)
Tial PCM) encoder 3-4, level detector (first and second volume detectors) 3-5, channel codec 3-6, ATT (attenuator) controller 3-7, and receiver 3-8. , Amplifier 3-9 and PCM decoder 3-1
0, a changeover switch 3-11, an ADPCM decoder 3-12, an ATT (attenuator) 3-13, an oscillator (background noise source) 3-14, a VOX controller 3-15,
Transmission signal processing unit 3-16 and reception signal processing unit 3-17
, A communication unit 3-18, and an antenna 3-19.

In this apparatus, the second volume detecting means of the level detecting section 3-5 for detecting the volume of the ambient noise input from the transmitter 3-1 immediately before starting the call, and the second volume detecting means Background noise volume adjusting means for adjusting the volume of background noise emitted from the oscillating unit (background noise source) 3-14 and transmitted to the receiver 3-8 based on the volume of ambient noise detected by Had been.

[0007]

In the background noise generator of the related art shown in FIG. 2, a background noise proportional to the power level of the received signal is generated at the timing of updating the background noise level. When an impulse noise or the like is input at the update timing, a background noise proportional to the magnitude of the impulse noise is generated, and a background noise that is not natural in auditory sense is generated such that the background noise suddenly increases or decreases. I was

[0008] In the PHS terminal shown in FIG. 3, the generation of the background noise is performed by changing the level of the sound signal taken in from the handset for about 0.5 seconds immediately before the start of a call in which the user is not talking. The detection unit uses the first and second volume levels as detection means, stabilizes, averages, and converts the sound signal, controls the ATT control unit based on the determination conversion value, and outputs the background noise output from the oscillation unit (background noise). The volume of is adjusted. This judgment conversion value is set each time a call state is entered, and when the call state is ended, it is held until the next call state, so that the background noise environment during the call is reduced. When it changes, the background noise cannot be heard at an appropriate level, and it may not be appropriate because it is too large or too small.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a background noise generating device that automatically generates a background noise that is not uncomfortable in hearing. .

[0010]

In order to achieve the above object, a background noise generating apparatus according to the present invention comprises a sound / silence determining circuit for judging sound or silence of a received signal, and a sound / silence judging circuit for judging whether the received signal is sound. A signal level detection circuit for detecting the power level of the received signal at a timing of switching to silence (referred to as "background noise level update timing"); and a received signal sampled at n background noise level update timings from the present to the past. A holding circuit for holding a weighted average signal level of the power level, a comparison circuit for comparing the average of the previous n samples held by the holding circuit with a change in the current reception signal level, depending comprising a control circuit for updating the background noise level, and the background noise generating circuit for generating a background noise on the receiving side, the, the reception signal when the reception signal is voiced Accept the output, when it is silent receiving side background noise level outputs <br/> background noise that is automatically set, it is characterized.

In the present invention, the control circuit for updating the background noise level on the receiving side compares the weighted average signal level for the previous n samples with the present received signal level to determine the change, and obtains the change. The background noise level of this time is updated by selecting one of a level up, a level down, and no level change for one step with respect to the background noise level of n samples.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of a background noise generating device according to an embodiment of the present invention.

Referring to FIG. 1, an embodiment of the present invention is a method of determining whether a received signal 1-1 is sound or silence.
A silence determination circuit 1-3, a signal level detection circuit 1-4 for detecting the power level of the received signal at a timing when the transmission signal 1-1 switches from speech to silence (referred to as "background noise level update timing"), To the past, the average signal level holding circuit 1-5 for n samples before holding the weighted average signal level of the power level of the received signal sampled at n background noise level update timings
A comparison circuit 1-6 for comparing the average of the previous n samples with a change in the received signal level this time; a control circuit 1-7 for updating the background noise level in accordance with the change; , A background noise generation circuit 1-8 that generates background noise, and a signal selected from the received signal 1-1 and the output of the background noise generation circuit 1-8, which are controlled by the output of the sound / non-speech determination circuit 1-3. And a multiplexer 1-2.

The operation of the embodiment of the present invention will be described below.

The reception signal 1-1 is a sound / non-speech determination circuit 1.
When it is determined that there is a sound by -3, the received signal is output as it is from the multiplexer 1-2.

When the received signal 1-1 is a sound / non-speech determination circuit 1-
When it is determined that there is no sound in Step 3, the background noise whose background noise level on the receiving side is automatically set internally is output from the background noise generation circuit 1-8.

The sound / non-speech determining circuit 1-3 determines the power level of the received signal by the signal level detecting circuit 1-4 at the timing when the received signal switches from voice to silence (referred to as "background noise level update timing"). To detect.

The power level of the received signal detected at the background noise level update timing is controlled by the control circuit 1-7, and the n samples stored in the weighted average signal level holding circuit 1-5 for the previous n samples are stored. The weighted average background noise signal level is compared with a comparison circuit 1-6.

After this comparison, the power level of the received signal detected at the present time is weighted and averaged with the power level of the received signal for the previous n samples, and a new weighted average signal level holding circuit 1 for the previous n samples is newly obtained. Stored and updated to -5.

The comparison circuit 1-6 compares the weighted average signal level of the previous n samples with the current received signal level, and as a result, the control circuit 1-7 obtains the change and obtains the background noise of the previous n samples. The current background noise level is updated by determining that the level is increased by one step, lowered by one step, or not changed (that is, updating of the background noise level is allowed only within a maximum of one step level). .

Here, the reason for changing only a maximum of one step is that the sound in the natural world has continuity without abrupt change, and even if sampling is performed in a short time, there is little change in the sample values before and after. is there.

The information on the background noise level updated by the control circuit 1-7 is input to the background noise generation circuit 1-8 and output as the background noise on the receiving side.

[0023]

As described above, according to the present invention,
Even if impulse noise or the like occurs at the timing of updating the background noise level, the background noise level fluctuates by at most one step with respect to the background noise level averaged over the past n samples, so that the background noise changes rapidly. Without this, a background noise that is not uncomfortable on the auditory sense is generated.

Therefore, according to the present invention, the background noise having an appropriate volume according to the surrounding environment can be output, and the device can be used in a noisy crowd or in a quiet environment without noise. However, the background noise of an appropriate size is output without annoying volume adjustment and the like, and the background noise that is not uncomfortable in terms of audibility is generated, and the VOX is generated.
This has the effect of improving the operability and convenience of a PHS, a mobile phone or the like having a function, and improving the usability.

[Brief description of the drawings]

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

FIG. 2 is a block diagram for explaining a conventional technique.

FIG. 3 is a diagram showing a known example referred to in Japanese Patent Application Laid-Open No. 8-79163.

[Explanation of symbols]

 1-1 Received signal 1-2 Multiplexer 1-3 Speech / silence determination circuit 1-4 Signal level detection circuit 1-5 Weighted average signal level holding circuit for previous n samples 1-6 Comparison circuit 1-7 Control circuit 1- 8 Background noise generation circuit 2-1 Received signal 2-2 Multiplexer 2-3 Speech / silence determination circuit 2-4 Signal level detection circuit 2-5 Background noise generation circuit 3-1 Speaker 3-2 Amplifier 3-3 PCM encoder 3-4 ADPCM encoder 3-5 Level detector 3-6 Channel codec 3-7 ATT controller 3-8 Handset 3-9 Amplifier 3-10 PCM decoder 3-11 Changeover switch 3-12 ADPCM decoder 3-13 ATT 3-14 Oscillator (background noise source) 3-15 VOX controller 3-16 Transmit signal processor 3-17 Receive signal processor 3-18 Communication Shinbe 3-19 Antenna

Claims (3)

(57) [Claims] 1. A sound / non-speech determination circuit for determining the presence or absence of sound in a received signal, and a power level of the received signal at a timing when the received signal switches from a sound to a silence (referred to as "background noise level update timing"). A holding circuit for holding a weighted average of the power levels of the received signals sampled at n times of the background noise level update timing from the present time to the past, and the holding circuit A comparison circuit for comparing the average of the previous n samples held in the above with the change in the received signal level this time, a control circuit for updating the background noise level according to the change, and generating the background noise on the receiving side A background noise generating circuit, and when the received signal is sound, outputs the received signal as it is,
Recipient background noise level are automatically set when a Silence
A background noise generator for outputting a background noise. 2. A control circuit for updating the background noise level on the receiving side, wherein a weighted average signal level for the previous n samples is compared with a current received signal level to obtain a change, and the background noise of the previous n samples is obtained. 2. The background noise generation device according to claim 1, wherein the background noise level is updated by selecting one of the levels up, down, or no level change for one step. 3. A terminal device for a PHS or mobile phone having a VOX function, comprising the background noise generating device according to claim 1.