JPH0771025B2 - Voice switch circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a voice switch circuit that realizes low insertion loss in a voice conference communication home device that performs voice conference communication using a speaker and a plurality of microphones. Is.

(Prior Art) Conventionally, this type of voice switch circuit is configured by a block diagram as shown in FIG. In Figure 2, 1 ₁ 1n the n number of microphones, 2 microphone mixer amplifier, the voice switch 3, 5 line amplifier, 6
Is a signal transmitting end, 7 is a signal receiving end, 8 is a receiving amplifier, 10 is a speaker amplifier, and 11 is a speaker.

If multiple microphones are placed in a meeting, etc.,
The ambient noise and the voice of the speaker are collected by each of the plurality of microphones _{11 to} 1n and input to the mixer amplifier 2. The mixer amplifier 2 is a microphone installed at a conference or the like.
Amplifies and outputs the sound and ambient noise collected by the total number of _{1 to} 1n. The output signal of the mixer amplifier 2 passes through a transmission channel insertion loss circuit 4 and is amplified by a line amplifier 5.
It is sent to the terminal 6. On the other hand, the reception signal input to the terminal 7 is amplified by the reception amplifier 8, and is received through the reception channel insertion loss circuit 9, the speaker amplifier 10, and the speaker 11. The voice switch control unit 12 detects the transmission / reception signals A / B branched from the transmission / reception channel, compares the levels of the signals, and removes the loss of the voice switch having the higher level. Then insert the voice switch loss at the lower level.

(Problems to be Solved by the Invention) However, the following are problems when sound is collected using a plurality of microphones having such a configuration. FIG. 3 schematically shows a situation in which the voice of the speaker C is collected when a plurality of microphones M _{1 to} M ₃ ( _{three in the} figure) are arranged in the room. In the figure, the solid line shows the direct sound of the speaker, and the broken line shows the indirect sound of the direct sound of the speaker C reflected by the wall in the room. In the situation as shown, the speaker C
The direct sound with a level sufficiently higher than that of the indirect sound is collected by the microphone M ₂ in front of the speaker, but the indirect sound and the direct sound collected by the microphones M ₁ , M ₃ farther from the speaker are The level difference becomes smaller. As a result, in the method of combining the outputs of the microphones M _{1 to} M ₃ and inputting them to the mixer amplifier 2, the ratio of the indirect sound to the direct sound increases as the number of microphones increases. The clarity of the voice is reduced. It is well known that such a phenomenon is more prominent in a room with larger reverberation.
Furthermore, since the output of all microphones is combined,
It is easy to collect noise and noise in the room, and S / N deterioration of the transmission signal may occur, or excess noise may be collected and the voice switch may malfunction, resulting in disconnection of the reception signal.

In order to avoid these problems, it is conceivable to use, for example, microphones 11 ₁ to ₁₆ with sharp directivity as shown in FIG. 4, but even in that case, the directivity of all the microphones 1 ₁ to ₁₆ is synthesized. Therefore, the operation is similar to that of one microphone having a wide directivity, and it becomes easier to collect indirect sound in the room. Further as to increase the number of microphones, easily collects received signal from the speaker, since the acoustic coupling of speaker 11 and a microphone 1 ₁ to 1 ₆ increases, has the disadvantage that tends to occur howling. In addition, in order to prevent howling, it is necessary to increase the insertion loss of the voice switch by the increase of the acoustic coupling amount. However, if this insertion loss of the voice switch is increased, the disconnection of the voice signal at the time of switching between transmitting and receiving. Is known to be significant.

On the other hand, it is conceivable to set a threshold value for each microphone and provide a gate circuit for each microphone that activates only the microphones that exceed the threshold value. However, in this method, if the threshold value is high, the amount of change in the gate ON / OFF loss is as large as several tens of dB to infinity, causing disconnection of the transmitted voice, and if the threshold value is low. Since a plurality of microphones are turned on at the same time, the amount of acoustic coupling between the microphones and the speaker increases, and it is not possible to eliminate the drawbacks such as howling.

Therefore, an object of the present invention is to adapt a voice switch for each transmission channel by individually comparing the levels of the transmission signals to each microphone using voice switches for all transmission channels of a plurality of microphones in a voice conference communication home device. S / N of the transmitted signal due to ambient noise and room reverberation
It is an object of the present invention to provide a voice switch circuit which solves the drawbacks such as deterioration, disconnection of a received signal by a voice switch due to extra noise, and a large insertion loss amount proportional to acoustic coupling between a speaker and a microphone.

(Means for Solving the Problems) The present invention has a configuration in which a voice switch circuit is applied to each transmission channel of a plurality of microphones in a voice conference communication in-home device for solving the above-mentioned problems, and transmission to each microphone is performed. Level comparison is performed on the individual speech signals, and only the transmission channels that are larger than the transmission threshold and larger than the reception signal level are removed by removing the insertion loss of the voice switch and operating only the minimum required microphone transmission channels. It is the one.

(Operation) Since the voice switch circuit is adapted to each transmission channel of a plurality of microphones in this manner, the microphone tracking operation can be individually performed according to the actual situation of the conference. Therefore, the above problems can be eliminated.

(Example) FIG. 1 is a diagram for explaining an embodiment of the present invention, 1 ₁ -
1 ₆ is, for example, 6 microphones, 2 ₁ to 2 ₆ are microphone amplifiers corresponding to ₆ microphones 1 ₁ to ₁₆ , 4 ₁
~ 4 ₆ transmission channel for insertion loss circuit provided for each transmission channel, 5 ₁ line amplifier transmitting to adding the transmission channel output, 6 is a transmitting end. Reference numeral 7 is a receiving end, 8 is a receiving amplifier, 9 is an insertion loss circuit for receiving channel, 10 is a speaker amplifier, and 11 is a speaker. Further, I _{1 to} I ₆ are signal branch ends of the respective transmitting channels, I ₇ is a signal branch end of the receiving channel, 13 is a voice switch control unit, and φ _{1 to} φ ₆ and φ ₇
Is a control signal terminal for controlling the voice switch loss amount of each transmission channel and the voice switch loss amount of the reception channel.

Next, the operation of this is described. The transmitted voice signals input to any of the microphones 1 ₁ to ₁₆ are amplified by the corresponding microphone amplifiers 2 ₁ to ₂₆ , and are inserted into the transmission loss channels 4 ₁ to 4 ₆ and the voice switch controller 13 To enter. The voice switch control unit 13 includes signal branch ends I _{1 to} I ₆ and
Whether or not the transmission / reception signal detected from I ₇ exceeds the transmission threshold and the level is higher than that of the reception signal is compared with each other to determine the level. Based on the above, the transmission / reception state of the voice switch loss to be controlled and the number of transmission channels to be enabled are determined, and the loss control signal is output to the control signal terminals φ _{1 to} φ ₇ according to both determination contents. Insertion loss circuit 4 ₁
It operates to set the amount of to 4 ₆ and 9.

Since the configuration and operation described above, when the voice of the example speaker in a conference microphone 1 ₃ is to have collected, the audio signal is detected in the voice switch control unit 13 f the microphone amplifier 2 _3. Voice switch controller 13
In comparing the transmission signal level from the input terminal I ₃ corresponding to the microphone 1 ₃ and transmission threshold, further performs reception signal level and the level comparison, if transmission signal level is determined to be larger than each, the insertion loss circuit 4 ₃ of the transmission channel is removed, the loss amount is 0 dB, that the insertion loss of the other transmission channel and the reception channel. If a loss is previously inserted in another transmission channel and reception channel, the loss is left unchanged. Thus, and only transmission channels of a single microphone 1 ₃ is operated. Also, when it is determined by one speaker that the insertion loss circuit of the microphone transmission channels of microphones 1 ₃ to ₁₂ is to be removed, the levels of both transmission channels are compared, and the larger one of them is selected. To operate. In addition, other speakers may say, for example, microphone ₁₆
And transmission towards, when applied to the conversation, the same determination processing as one microphone is made, the insertion loss circuit 4 ₆ of the transmission channel and 0 dB, and enable two microphones. At this time, if the maximum number of valid microphones is set in advance, it is possible to freely select 1 to 6 microphones.

Generally, when a plurality of microphones are arranged in a state where they do not interfere with each other, the increase in the level of noise and reverberant sound collected by the plurality of microphones is as follows compared to the case of one microphone [LL Rayleigh, Theory of Sound, Vol-1,2nd ed, Macmil
lar, London.1929, P.36] 20log (| M ₁ ＋ M ₂ ＋ M ₃ ＋… ＋ M _n |) / | M ₁ | ＝ 10olg (n) where M ₁ , M ₂ , M ₃ , ,, M _n is the output of each microphone. N is the total number of microphones.

Therefore, in the present embodiment, since only one microphone is activated in advance according to the speaker, an S / N improvement effect of about 8 dB can be expected as compared with the case where all six microphones are activated.

If only two can be activated at the same time, an improvement of about 5 dB can be expected. In the present embodiment, the case where the number of microphones is 6 is shown, but a larger amount of improvement can be expected as the number of microphones increases. For example, in a conference or the like, it is extremely rare for two or more people to speak at the same time, so applying a voice switch circuit having such a configuration to a conference device is effective in improving S / N. Further, as a great effect, this system configuration can reduce the amount of acoustic coupling between the speaker and the microphone. That is, since a loss is inserted for each microphone, the acoustic coupling amount is equivalent when there are only h microphones (h is the number of microphones that are active during transmission). As a result, the depth of loss actually switched by the voice switch is 10log (n) compared to the conventional example in which all n microphones are activated.
It can be reduced by -10log (h) (dB). As a result, the feeling of disconnection of the voice can be eliminated by the amount that can be reduced.

(Effects of the Invention) As described in detail above, by adapting the voice switch circuit for each transmission channel of a plurality of microphones, the microphone tracking operation according to the actual situation of the conference is individually performed, and the transmission by the indoor noise is performed. Prevents S / N deterioration of audio signals,
There are advantages that the echo feeling due to the reverberation in the conference room is removed, S / N deterioration is prevented, and unnecessary noise such as page turning sound of the material is removed. Furthermore, there is an effect that the amount of voice switch insertion loss due to improvement of acoustic coupling can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of an in-home device of the present invention, FIG. 2 is a block diagram of an example of an in-home device equipped with a conventional voice switch circuit, and FIG. 3 is an indoor view in which three microphones are installed. Explanatory diagram showing how direct sound and indirect sound are collected,
FIG. 4 is a diagram showing an arrangement of directional characteristic examples of the six microphones in FIG. 1 ₁ ~ 1 _n ... Microphone, 2,2 ₁ ~ 2 ₆ ... Microphone mixer amplifier, 3,3 ₁ ... Voice switch circuit, 4, 4 ₁ ~ 4 ₆ ...
… Transmission channel insertion loss circuit, 5 …… Line amplifier, 5 ₁ …
… Line amplifier also serving as a transmission channel mixer, 6 …… Transmission end, 7 …… Reception end, 8 …… Reception amplifier, 9 …… Reception channel insertion loss circuit, 10 …… Speaker amplifier, 12,13 ...
… Voice switch controller, I _{1 to} I ₇ …… Signal branching terminal, φ ₁
~ Φ ₇ ...... Insertion loss control signal output end.

Claims (1)

[Claims] 1. A voice switch circuit of a voice conference communication in-home device for performing a conference call using a speaker and at least two or more microphones, wherein a microphone amplifier and an insertion loss circuit are connected to the microphones, respectively. Line amplifier that forms a plurality of transmission channels by adding the outputs of the respective transmission channels, a reception amplifier that amplifies the reception signal, and a reception channel insertion loss connected to the output of the amplifier. A reception channel is formed by a circuit, a speaker amplifier and a speaker connected via the insertion loss circuit, and a plurality of inputs connected to the output of each microphone amplifier and a transmission channel insertion loss circuit are connected. A plurality of outputs, and an input connected to the output of the receiving amplifier and an insertion loss circuit for the receiving channel. The output level of each of the microphone amplifiers and the output level of the reception amplifier are compared, and when the output level of at least one or more microphone amplifiers is higher than the output level of the reception amplifier, A voice switch circuit provided with a voice switch control unit for individually performing microphone tracking operations by removing insertion loss of a transmission channel and inserting losses in other transmission channels and reception channels.