JPH0657031B2 - Conference call equipment - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conference call device that allows a plurality of listeners to hear the voices of a plurality of talkers.

(Prior Art) In this type of conventional conference call device, for example, in a transmission system, microphones are installed for a plurality of conference participants (speakers), and the audio signals output from the microphones are mixed. A single mixed voice signal is synthesized by an amplifier and sent out.
The reproduction is performed at the same level from one speaker or a plurality of speakers.

However, in the above apparatus, since the voices of a plurality of conference participants of the transmitting system all come from the same direction in the receiving system, the selective listening ability of the characteristic voice due to the binaural listening characteristic of human beings deteriorates. There was a problem of lack of realism.

As a device that solves the above problems, there has been a device that introduces a 2-channel stereo system. That is, in this device, in the transmission system, the audio signals output from the respective microphones installed corresponding to the plurality of conference participants are distributed to the left channel signal and the right channel signal according to the left and right installation positions of the microphones and received. In the system, the left and right channel signals are reproduced from two speakers respectively.

(Problems to be solved by the invention) By the way, in order to improve the selective listening ability of characteristic voices and to give a sense of presence, the voices of the participants of each conference in the transmission system are localized in different directions, and it is as if In the receiving system, each conference participant gives the impression that they are present side by side on the speaker side in the receiving system, that is, the individual sound images of each conference participant are separated and localized. Is the most effective.

However, in the device using the two-channel stereo system, each sound image can be separated and localized for the listener located near the center of the two speakers in the receiving system, as described above. However, in other listeners not located near the center of the two speakers, the so-called preceding sound localization, in which the sound images of all conference participants in the transmission system are localized in the speaker closer to each listener. However, there is a problem that it is not possible to separate and localize the sound images of a plurality of conference participants of the transmitting system to all the conference participants of the receiving system.

An object of the present invention is to eliminate the above-mentioned problems and to provide an apparatus capable of allowing all conference participants of a receiving system to separate and localize the sound images of each conference participant of a transmitting system and listen. To do.

(Means for Solving Problems) In the present invention, in order to solve the above problems, a transmission system that collects voice signals of a plurality of talkers by a plurality of microphones and sends the voice signals to a transmission path. In a conference call device including a receiving system that receives the voice signal from the transmission path, reproduces the plurality of speakers with a plurality of speakers, and is heard by a plurality of listeners, in the transmitter system, the number of speakers corresponding to the number of speakers is included. A microphone, a two-channel mixing circuit that creates a two-channel stereo signal from a plurality of audio signals picked up by each of the microphones, a level detection circuit that detects an average level value of the plurality of audio signals, and a plurality of the level detection circuits. A signal generating circuit for generating a control signal including information based on the average level value of the audio signal is provided, and the receiving system has a number of speakers corresponding to the number of speakers and the two-channel speaker. A plurality of mixing amplifiers for mixing teleo signals at a predetermined ratio, a plurality of variable gain amplifiers for amplifying respective output signals of the plurality of mixing amplifiers with arbitrary gains, and outputting the amplified signals to the respective speakers, and the control signal. And a control circuit for controlling the gain in each of the variable gain amplifiers according to the reception.

(Operation) According to the present invention, in the transmitting system, a plurality of audio signals picked up by the respective microphones are converted into 2-channel stereo signals by the 2-channel mixing circuit and sent to the receiving system. An average level of each of a plurality of audio signals is detected, and a control signal including information based on each average level value is sent to the receiving system, and the two-channel stereo signals are mixed at a predetermined ratio in the receiving system, These are amplified with an arbitrary gain and output to each speaker corresponding to each of the microphones, and the gain is controlled by the control signal. For example, a speaker having a large level is used for a speaker corresponding to a microphone of a main speaker. An audio signal is output.

(Embodiment) FIGS. 1 and 2 show an embodiment of the present invention.
FIG. 1 shows the structure of a transmitting system, and FIG. 2 shows the structure of a receiving system. It should be noted that since a conference call is normally performed in two directions, two transmission systems and a reception system are required, but since the contents are the same, a one-way device will be described.

In FIG. 1, 11-1, 11-2, ... 11-n are transmitters, 12-1, 12-2, ... 12-n are microphones, 13 is a two-channel mixing circuit, 14-1,
14-2, ... 14-n is a level detection circuit, 15 is a signal generation circuit, 16 and 17 are output terminals of left channel signals and right channel signals of 2-channel stereo signals, and 18 is an output terminal of control signals.

The microphones 12-1 to 12-n are installed in the vicinity of the plurality of talkers (conference participants) 11-1 to 11-n attending the conference.

The 2-channel mixing circuit 13 includes a distribution (panpot) circuit 131-1, 131-2, ... 131-n and an adder 13
2, 133 and each microphone 11-1 to 11-n
The audio signals of the respective channels, which are picked up by the and converted into the electric signals, are distributed to the left channel and the right channel by the distribution circuits 131-1 to 131-n at a ratio according to the relative positions of the microphones 12-1 to 12-n. Distribute to each channel signal,
The respective left channel signals and the respective right channel signals are added by adders 132 and 133, respectively, and output to output terminals 16 and 17.

The level detection circuits 14-1 to 14-n are, for example, smoothing (integrating) circuits having a predetermined time constant, and send the average level value of the audio signal of each channel to the signal generating circuit 15.

The signal generating circuit 15 is composed of, for example, a microprocessor, encodes the average level value of each channel by using a BCD code or the like, generates a control signal in which these are arranged in the order of channel numbers, and outputs the control signal to the output terminal 18. Send out. Note that this operation is repeated at regular intervals, and a control signal having information on the average level value for each channel at that time is always created.

The signals at the output terminals 16, 17, and 18 are transmitted as they are, or after being multiplexed or further modulated, transmitted to a transmission path (not shown) and transmitted to a reception system.

In FIG. 2, reference numeral 21 is an input terminal for a left channel signal of a two-channel stereo signal, 22 is an input terminal for a right channel signal, 23 is an input terminal for a control signal, and 2 is an input terminal.
4-1, 24-2, ... 24-n is a mixing amplifier,
Reference numeral 25 is a control circuit, 26-1, 26-2, ... 26-n is a variable gain amplifier, 27-1, 74-2, ... 27-n is a speaker, 28-1, 28-2 ,. -M is the listener.

The two-channel stereo signals of the left channel and the right channel and the control signal sent via the transmission line are input to the input terminals 21, 22 and 23, respectively.

The mixing amplifiers 24-1 to 24-n have input terminals 21.
The left channel signal from the input terminal 22 and the right channel signal from the input terminal 22 as input signals, and these are mixed at a predetermined ratio according to the relative positions of the corresponding microphones 12-1 to 12-n of the transmitting system, Variable gain amplifier 26-
1 to 26-n, respectively.

The control circuit 25 is composed of, for example, a microprocessor, receives a control signal from the input terminal 23, converts information representing the average level value of the audio signal for each channel into a voltage signal, and converts these into a voltage signal. 26-1 ~
26-n respectively.

The variable gain amplifiers 16-1 to 26-n are, for example, well-known voltage controlled amplifiers (VCA), and output signals of the mixing amplifiers 24-1 to 24-n according to the voltage signal from the control circuit 25. It is amplified by the gain and sent to the speakers 27-1 to 27-n.

The speakers 27-1 to 27-n are arranged corresponding to the channel numbers in the same order as the microphones 12-1 to 12-n.

The number n of the microphones 12-1 to 12-n is equal to the number n of the transmitters 11-1 to 11-n, and this is equal to the number n of the speakers 27-1 to 27-n of the receiving system. Although equal, the number m of the listeners 28-1 to 28-m is independent of n.

Next, the operation will be described.

Usually, there is only one main speaker, although several people may speak at the same time during a meeting. The voice uttered by the main speaker, for example, 11-2 reaches the microphones 12-1 to 12-n and the sound pressure level corresponding to the distance between the seat position and the microphones, and therefore corresponds. The microphone 12-2 converts the voice signal to the highest level, and the other microphones convert the voice signal to a lower level for a microphone located farther from the sender 11-2.

The audio signal of each channel from each of the microphones 12-1 to 12-n is supplied to the 2-channel mixing circuit 1.
At 3, the signals are converted into left-channel and right-channel stereo signals, sent to output terminals 16 and 17, and input to level detection circuits 14-1 to 14-n.

The audio signals of the respective channels are level detection circuit 14-
At 1 to 14-n, the average level value is detected and sent out by the signal creating circuit 15. The signal creating circuit 15 creates a control signal including information indicating the average level value for each channel, and sends it to the output terminal 18. At this time, as described above, the average level value of the channel corresponding to the microphone 12-2 is the largest, and becomes gradually smaller as it goes away from it, and the control signal includes these pieces of information.

In the receiving system, the left channel signal and the right channel signal of the 2-channel stereo signal are input to the input terminal 21.
And 22 to mix amplifiers 24-1 to 24-n
Are input at a predetermined ratio. Further, the control signal is input to the control circuit 25 from the input terminal 23, where the information indicating the average level value for each channel is converted into a voltage signal.

The plurality of voltage signals are supplied to the gain control amplifiers 26-1 to 26-
n, the voltage value of which is transmitted to the microphone 12
The voltage signal of the channel corresponding to -2, that is, the voltage signal input to the gain control amplifier 26-2 is the largest, and becomes gradually smaller as the distance from this becomes larger. Therefore, the gain in the gain control amplifier 26-2 is the largest, and becomes gradually smaller as it goes away.

At this time, the main speaker 11
-2 sound is reproduced greatly, and another speaker 27-1,
.. In 27-n, the voice of the main speaker 11-2 is gradually reduced as it leaves the speaker 27-2. Therefore, the voice of the main speaker 11-2 receives all the received voices. The speakers 28-1, 28-2, ... 28-m are localized in the speaker 27-2 and are heard separately from the voices of other speakers.

When the main speaker changes, the level detection circuit 14-
The average level value of the audio signal of each channel output from 1 to 14-n changes, and the average level value of each channel at this point is immediately created and sent by the signal creating circuit 15, and the next main transmission The voice is reproduced louder than the speaker corresponding to the speaker, and is localized at a fixed position for all the listeners as described above, and is heard separately from the voices of other speakers.

Also, two or more talkers, for example, talkers 11-1 and 11-.
When n and n are simultaneously transmitted, if the gains of the variable gain amplifiers 26-1 to 26-n are the same as in the conventional case, the receiver 28
For the speakers other than the listener near the center of -1 to 28-m, the speaker 11-1 is connected to the speaker closest to the speaker.
Although the two sound images 11 and 11-n are localized without being sufficiently separated, according to the present invention, the variable gain amplifiers 16-1 and 16-2 are used.
The gain in 6-n becomes the largest, and the gain gradually decreases as the distance from the two is increased, that is, as the distance from the center is approached, the gain gradually decreases, and for all the listeners 28-1 to 28-m,
It is possible to localize the sound image of the speaker 11-1 near the speaker 27-1 and the sound image of the speaker 11-n near the speaker 27-n.

In the above embodiment, the signal including the information indicating the average level value for each channel is used as the control signal, but in the transmission system, the average level value for each channel is compared with a predetermined threshold value, and the threshold value is In the above cases, there is "sending"
If it is smaller than the threshold value, it is determined that there is no transmission,
It is also possible to use a signal containing information indicating the presence or absence of transmission. In this case, in the receiving system, the gain of the variable gain amplifier of the channel determined to be “no transmission” is set to “0”,
That is, the same operation as that of the above-described embodiment can be obtained by cutting off the output and setting the gain of the variable gain amplifier of the channel determined to have "talk" to a predetermined value.

As described above, according to the present invention, in the receiving system,
Since the voice of each speaker can be reproduced from the speaker corresponding to the position of each speaker, the sound image of each speaker can be separated and localized for all the listeners. Even when the speakers talk at the same time, the sound images of the speakers can be separated and localized, and the selective listening ability of the specific voice and the realism can be improved.

[Brief description of drawings]

1 and 2 show an embodiment of the conference call apparatus of the present invention. FIG. 1 is a diagram showing a configuration of a transmitting system and FIG. 2 is a diagram showing a configuration of a receiving system. 11-1, 11-2, ... 11-n; Talker, 12-
1, 12-2, ... 12-n; Microphone, 13; 2
Channel mixing circuit, 14-1, 14-2, ...
14-n; level detection circuit, 15; signal generation circuit, 1
6; output terminal for left channel signal, 17; output terminal for right channel signal, 18; output terminal for control signal, 21; input terminal for left channel signal, 22; input terminal for right channel signal, 23; input for control signal Terminals, 24-1, 24
-2, ... 24-n; mixing amplifier, 25; control circuit, 26-1, 26-2, ... 26-n; variable gain amplifier, 27-1, 27-2, ... 27-m; speaker Two
8-1, 28-2, ... 28-n; listener.

Claims (1)

[Claims] 1. A transmission system for collecting voice signals of a plurality of talkers by a plurality of microphones and transmitting the voice signals to a transmission path.
In a conference call device comprising a receiving system which receives the voice signal from the transmission path, reproduces it by a plurality of speakers, and is heard by a plurality of listeners, the number of microphones corresponding to the number of speakers is provided in the transmitting system. A two-channel mixing circuit that creates a two-channel stereo signal from a plurality of audio signals picked up by each microphone, a level detection circuit that detects an average level value of each of the plurality of audio signals, and the plurality of audio signals. A signal generation circuit for generating a control signal including information based on the average level value of the signal is provided, and the number of speakers corresponding to the number of talkers and the stereo signals of the two channels are respectively set in the reception system in a predetermined manner. A plurality of mixing amplifiers that are mixed at a ratio and each output signal of the plurality of mixing amplifiers are amplified with an arbitrary gain and output to each of the speakers. A plurality of variable gain amplifier, receives the control signal, a conference call apparatus is characterized by providing a control circuit for controlling the gain in each of the variable gain amplifier in response thereto.