JPS6313563A - Conference talking transmission and reception equipment - Google Patents

Abstract

PURPOSE:To send a clear voice by dividing a large conference room into two zones, coupling and distributing transmission/reception circuits provided respectively to both the zones and controlling a gain by both the transmission/ reception circuits to operate an echo canceller stably. CONSTITUTION:A large conference room is divided into two zones A, B. An electric signal generated from microphones 1A,1B enters a level detection circuit 7 through echo cancellers 4d, 4b and 4a, 4c, the voice signal received from an opposite conference room enters the level detection circuit 7 via an A/D 11, where the level of each voice signal is detected. A gain control circuit 8 receives information of the large/small quantity and gain variable circuits 6a-6c give a gain or loss to the voice signal. The output signal of a gain variable circuit 6a is added to an output signal of a gain varying circuit 6b by an adder 50 in a branch circuit 5 and sent through a D/A 14. When the gain variable circuits 6a, 6b are lost, crosstalk signals a, d, and b, c from speakers 2A, 2B are reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a conference call transmitting/receiving device, and more particularly to a conference call transmitting/receiving device for transmitting and receiving audio signals to and from a distant conference room.

[Conventional technology]

After mixing the audio signals emitted from the icrophone,
The audio signal is guided to multiple transmitting circuits, amplified, etc., and transmitted to the other party, and is also amplified into the same room through a branch circuit.In the receiving section, the audio signal sent from the other party is amplified by multiple receiving circuits, and then sent to a public address system. guiding.

In order to prevent echoes and howling from occurring due to audio looping from the speaker of the public address system to the transmitting microphone,9 usually multiple echo cancellers are connected between the transmitting circuit and the receiving circuit. This removes the indoor echo components that occur due to wraparound.

[Problem that the invention seeks to solve]

In the conventional conference call transmitting/receiving device as described above.

In particular, in the same-room public address function, the size of the room echo caused by audio looping from the speaker to the microphone depends on the positional relationship between the speaker and microphone, the number of microphones placed, and the directivity. It is also conceivable that the limit of the erasing performance is exceeded and echoes and howling become more likely to occur. Furthermore, as the number of microphones increases, room noise is added through the microphones, and the S/N ratio of this room noise N to the signal S to be transmitted deteriorates.
The disadvantage is that clear voice transmission cannot be achieved.

An object of the present invention is to solve the above-mentioned problems, and to stably operate an echo canceller without causing reverberant echo or howling even in the same room amplification.

An object of the present invention is to provide a conference call transmitting/receiving device capable of transmitting clear audio.

[Means for solving problems]

The device of the present invention has a plurality of zones, and includes a plurality of transmitting circuits for respectively guiding audio signals sent from microphones in each zone of a conference room, and a plurality of transmitting circuits for respectively guiding audio signals sent from microphones in each zone of a certain conference room, and for guiding audio signals sent from the conference room of the other party. a plurality of receiving circuits for guiding signals to the speakers in each of the zones; and a plurality of receiving circuits for generating a pseudo echo signal for canceling indoor echo in response to an audio signal given from one of the receiving circuits, and one for transmitting the signal. echo canceling means for connecting an echo canceller for subtracting from the audio signal passing through the circuit between the receiving circuit and each transmitting circuit; and level detection for detecting the level of each audio signal and comparing the magnitude relationship. circuit and
A plurality of variable gain circuits that vary the level of each of the audio signals, a gain control circuit that receives information output from the level detection circuit and controls each of the variable gain circuits, and a plurality of variable gain circuits that control each of the variable gain circuits; It is configured to include a branch circuit that adds signals to each other and transmits the signal to the other party, and distributes the audio signal sent from the other party to each of the receiving circuits.

〔Example〕

Next, nine aspects of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. The large conference room is divided into two zones, A7''□- and B zone, and microphone I is used for sending and receiving calls in zone A.
Zone A and speaker 2A, and microphone IB and speaker 2B for zone B are installed. An electrical signal generated from the microphone IA in response to a call in the A zone is sent to the amplifier circuit 3A. Since the conference room is large, multiple microphones IA are installed in the A zone, and the amplifier circuit 3A is a mixing amplifier that adds and amplifies the electrical signals sent from the multiple microphones IA. .

The electrical signals mixed by the amplifier circuit 3A are as follows.

Analog-digital converter (hereinafter abbreviated as A/D) 10
After being converted into a digital signal by the echo canceller 4
d and 4a, and enters the variable gain circuit 6a and level detection circuit 7. Similarly, the electric signal generated by microphone IB is mixed by amplifier circuit 3B, and then
The signal is converted into a digital signal by the A/D 12, passes through echo cancellers 4b and 4C, and enters variable gain circuit 6b and level detection circuit 7.

On the other hand, the audio signal received from the other party's conference room via the communication line is converted into a digital signal by the A/Dll and input to the variable gain circuit 6c and level detection circuit 7. The level detection circuit 7 detects the level of each input audio signal and compares the magnitude relationship. The information output from the level detection circuit is led to the gain control circuit 8, which sets each audio signal level to an appropriate value. The level detection circuit 7 detects the sum of the products of the squares of the amplitude values of the audio signal as the average power of the audio signal, and outputs the levels of the plurality of input signals to the gain control circuit 8 as information on the order of magnitude. The gain control circuit 8 receives the information, and the variable gain circuit 6 B + 6 b +
6c gives dyne or loss to the audio signal.

The output signal of the variable gain circuit 6a is transmitted to the other party's conference room via the communication line in the branch circuit 5.

A call signal received from the other party's conference room via the communication line is converted into a digital signal by the A/Dll, and then sent to adders 51 and 52 in the first branch circuit 5. Adder 51 (
Alternatively, 52) adds this received signal and the signal sent from variable gain circuit 6b (or variable gain circuit 6a) and sends the result to D/A 13 (or D/A 15).

The signal output from the adder 51 (or 52) is D/
Along with being sent to A13 (or 15).

It is also sent to echo cancellers 4a and 4b (or 4c and 4d). The signal converted to analog by D/A 13 (or 15) is sent to amplifier 5A (or 6B).
After being amplified, the signal is sent to the speaker 2A (or 2B) and output as audio.

A portion of the audio transmitted from speaker 2A is as follows.

As shown by the solid line arrow a, the signal goes around to the microphone IA in the local zone, and also goes around to the microphone IB in the other zone, as shown by the broken line arrow. Similarly,
The sound output from the speaker 2B also goes around to the microphone IB and the microphone IA, as shown by the solid line arrow C and the broken line arrow d, respectively.

The echo cancellers 4a, 4b, 4c, and 4d are provided to remove indoor echoes caused by the above-mentioned echo feedback. For example, the echo canceller 4b receives a signal led from two speakers, that is, a signal sent from an adder 51, generates a pseudo echo signal in an adaptive filter 40, and a subtracter 41 receives a signal led from a microphone IB, that is, an A/ The pseudo echo signal is subtracted from the transmitted signal of D12. The signal obtained as a result of this subtraction is sent to the subsequent echo canceller 4c, and is also sent to the adaptive filter 40 as an error signal indicating the degree of echo cancellation. The adaptive filter 40 is a transbazaar filter that adaptively controls tap coefficients in response to an input signal and an error signal so that the value of the error signal converges to zero.

Usually, during initial training, a prescribed number of J? A training signal i with a turn is given to the D/A 13 and the echo canceller 4b, and in response, a signal sent from the A/D 12 by audio looping indicated by the dashed arrow is
The adaptive operation of the adaptive filter 40 is converged so that the subtracter 41 of the echo canceller 4b substantially cancels the signal. During a conference call after training, A/D1
．． The signal sent from 2 to echo canceller 4b is 9
This corresponds to the sum of two components that respectively correspond to the voice of the speaker and the voice coming from the two speakers via the route indicated by the broken line arrows. The echo canceller 4b cancels and sends out the components corresponding to the latter, and eliminates the room echo caused by the sound feedback indicated by the broken line arrow, when the two speakers reproduce the sound.

To prevent reverberation echo and howling from occurring.

The echo cancellers 4a, 4c, and 4d also have the same configuration as the z-canceller 4b, and are indicated by solid line arrows a, respectively.
This is provided to eliminate indoor echoes caused by sound looping as shown by e and broken line arrows.

In addition, the plurality of variable gain circuits are used to reduce the amount of sound reflected from the speaker to the microphone in order to make this echo cancellation operate more stably than the echo cancellation in conventional conference call transmitting/receiving devices. The level detection circuit outputs the magnitude order of each audio signal output from 4a and 4CA/Dll. A variable gain circuit applies dyne to the signal with the highest level, and loss to the other signals. (Those dynes and losses can be set in advance.) That is.

When the variable gain circuits 6a and 6b are in a loss state, they reduce the amounts of the loop signals a and d, and the loop signals c and b, respectively. It is clear that when loss occurs in the variable gain circuits 6a and 6b, the room noise transmitted to the other party's conference room is reduced.

f18) As explained above, in this embodiment, a large conference room is divided into two zones, a transmitting/receiving circuit is provided in each of the nine zones, and the branch circuit 5 connects and distributes the two transmitting/receiving circuits. By simultaneously controlling the gain and removing indoor echoes occurring within each zone and between both zones, it is possible to obtain an echo cancellation function within the device more stably than in the past.

Embodiments of the present invention are listed below.

(2) A conference call according to claim 1, characterized in that it has a level comparison circuit that compares the magnitude relationship of the audio signals, and controls the gain of the plurality of variable gain circuits based on the magnitude relationship of the levels. Transmitting/receiving device.

〔Effect of the invention〕

As explained above, the present invention has the advantage of being able to realize a conference call transmitting/receiving device that can cover the entire room without causing reverberant echoes or howling even in large conference rooms.

Margin below

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention. 1, A, IB...Microphone, 2A, 2
B...Speaker, 3A, 3B...Amplification circuit r 4a+4b+4c+4d...Echo canceller, 5...Branch circuit, 50-52...Addition circuit, 6
A, 6B... Amplifier, 10-12... Analog-digital converter, 13-15... Digital-analog converter, 6a, 6b, 6c... Variable gain circuit, 7.
... Level detection circuit, 8... Gain control circuit.

Claims (1)

[Claims] (1) A conference room with multiple zones has multiple transmitting circuits for guiding the audio signals sent from the microphones in each zone, and a plurality of transmitting circuits for guiding the audio signals sent from the microphones in each zone, and for guiding the audio signals sent from the conference room of the other party. a plurality of receiving circuits for respectively guiding the sound signals to the speakers in the zone; and generating a pseudo echo signal for canceling room echo in response to an audio signal given from one of the receiving circuits, and passing the signal through one of the transmitting circuits; echo canceling means that connects an echo canceller for subtracting from the audio signal between the receiving circuit and each of the transmitting circuits for each of the receiving circuits; a level detecting circuit that detects the level of each of the audio signals and compares the magnitude relationship; a plurality of variable gain circuits that vary the level of each of the audio signals, a gain control circuit that receives information output from the level detection circuit and controls each of the variable gain circuits, and audio guided from each of the gain control circuits. 1. A conference call transmitting/receiving device comprising a branch circuit that adds signals to each other and transmits the signal to the other party, and distributes an audio signal sent from the other party to each of the receiving circuits.