JP2637106B2 - Audio conference equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention] (Industrial application field) The present invention relates to a voice conference apparatus for conducting a conference by a loudspeaker call via a telephone line or a dedicated line using a speaker and a microphone. is there.

2. Description of the Related Art Conventionally, as shown in a block diagram of FIG. 2, this type of audio conference apparatus transmits an audio signal from a conference partner input to an audio input path 1 via a line (not shown). Echo canceling circuit 2
The signal is input to an amplifier circuit 4 via a gain variable circuit 3, and the amplifier circuit 4 amplifies the input audio signal so as to have a predetermined volume level. Alternatively, audio signals input from a plurality of microphones 6a, 6b assigned to several persons are amplified by amplifier circuits 7a, 7b, respectively, and then combined by an adder circuit 8, and the echo canceler circuit 2 and the audio transmission path 9 Through a wired line (not shown).

The echo canceling circuit 2 is for canceling a sneak signal caused by acoustic coupling between the speaker 5 and the microphones 6a and 6b.
For example, it is composed of an adaptive filter such as an adaptive finite impulse response filter. The echo canceling circuit 2 requires a learning operation to know the characteristics of the echo path when canceling the sneak signal. For this reason, a training signal is generated from the speaker 5, whereby the characteristic of the echo path is detected, and a parameter for canceling the sneak signal is set according to the characteristic.

However, in the echo canceling circuit 2, if the level of the echo signal with respect to the original signal exceeds a predetermined value, it becomes difficult to cancel the wraparound component.

Therefore, in the conventional configuration shown in FIG. 2, the gain variable circuit 3 is inserted into the input path of the speaker 5, and the addition circuit 8
The output level of the audio signal output from the gain control circuit 10
When the output signal level of the adder circuit 8 becomes equal to or higher than the level at which the echo canceling circuit 2 cannot cancel the sneak component, the gain of the variable gain circuit 3 is reduced to cancel the sneak component. It is configured as follows.

The gain control circuit 10 is configured to operate only when the control signal input from the input terminal 11 is, for example, “L” level.

(Problems to be Solved by the Invention) However, since the above-described conventional device is configured so that the volume of the speaker 5 can be lowered and the echo canceling circuit 2 can cancel the sneak component, a plurality of microphones are required.
If at least one of 6a and 6b is close to speaker 5,
The gain of the variable gain circuit 3 is greatly reduced by the acoustic coupling. As a result, the volume of the sound generated from the speaker 5 is reduced, and there has been a problem that the content cannot be heard.

An object of the present invention is to provide an audio conference apparatus that can generate a sound of sufficient volume from a speaker even when a speaker and a microphone are close to each other and can smoothly proceed with a conference.

[Constitution of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a speaker for generating an audio signal transmitted from a conference partner via a line as an audible sound, A plurality of microphones for inputting voice for a call and transmitting the voice to a conference partner via a line; a voice signal input path to the speaker and a voice signal transmission path by the microphone; An echo canceling circuit for canceling a sneak signal due to acoustic coupling of a sound signal, and a characteristic of the echo canceling circuit is detected by generating a predetermined training signal from the speaker, and a parameter of the echo canceling circuit is changed according to the detected characteristic. Setting means for setting, wherein a plurality of gains provided on respective output sides of the plurality of microphones are provided. And a predetermined reference corresponding to a level at which a wraparound signal by the echo canceling circuit can be canceled out of output audio signal levels from the plurality of microphones when the predetermined training signal is generated from the speaker. And a gain control circuit that controls the gain variable circuit so that the output audio signal level from the microphone becomes equal to or less than the predetermined reference value when there is a value exceeding the value.

(Operation) The output sound signal levels of the plurality of microphones are controlled by the gain control circuit so that the levels become equal to or lower than a predetermined level. Therefore, if a specific microphone is approaching the speaker, the output audio signal level of the specific microphone may exceed a predetermined value due to acoustic coupling with the speaker. Only the output audio signal level of the microphone is lowered and controlled to a predetermined level or less. Therefore, the level of the audio signal input to the echo canceling circuit is always lower than the predetermined level, and it is possible to cancel the sneak component without reducing the volume of the speaker.

FIG. 1 is a block diagram showing one embodiment of the present invention.
2 are indicated by the same symbols. 1 is different from the conventional configuration of FIG. 2 in that the amplifier circuits 7a and 7b
The variable gain circuits 13a and 13b are inserted on the output side of the amplifier circuit 7 and the output audio signal levels of the amplifier circuits 7a and 7b are monitored. , 13b, and a signal transmitting circuit 14 for transmitting a predetermined training signal to the audio input path 1, a gain variable circuit 3 for varying the input signal level of the speaker 5, and a gain control circuit. That is, the circuit 10 is deleted.

Here, the gain control circuit 12 and the signal transmission circuit 14 operate when the control signal input from the input terminal 11 is at "L" level.

In the above configuration, when the control signal input to the input terminal 11 is changed to “L” level, the gain control circuit 12 sets the gains of the gain variable circuits 13a and 13b in advance in synchronization with the fall of the control signal. A gain setting signal for setting a predetermined gain is output. Thereby, the gains of the gain variable circuits 13a and 13b are set to a predetermined gain.

On the other hand, the signal transmission circuit 14 starts operating when the control signal falls to the “L” level, and transmits a predetermined training signal to the audio input path 1. This training signal is input to the amplifier circuit 3 via the echo canceling circuit 2, where it is amplified as audible sound from the speaker 5 after amplification. The audible sound of the training signal is received by the microphones 6a, 6b and output from the amplifier circuits 7a, 7b.

At this time, the gain control circuit 12 compares the signal level input from the amplifier circuits 7a and 7b with the reference value, and for a signal having a level higher than the reference value, the corresponding gain variable circuit (13a,
13b), the gain is reduced, and a gain setting signal is calculated such that the input level to the adding circuit 8 becomes equal to or lower than the reference value. And
When the control signal input from the input terminal 11 returns from "L" to "H", the gain setting signal calculated at the time of rising is held and then applied to the corresponding gain variable circuits (13a, 13b).

As a result, the gain variable circuits 13a and 13b are controlled to a gain such that the input level to the adder circuit 8 becomes equal to or less than the reference value regardless of the acoustic coupling conditions between the corresponding microphones 6a and 6b and the speaker 5.

Here, the reference value used in the control circuit 12 is set to the echo canceling circuit 2
In this case, the wraparound component can be canceled irrespective of the acoustic coupling conditions between the microphones 6a and 6b and the speaker 5 by making the wraparound component correspond to the cancelable level of the wraparound component. In this case, since the volume of the speaker 5 is fixed at the gain set in the amplifier circuit 4, sound from the other party can be generated at a sufficient volume.

By scanning the training signal output from the signal transmission circuit 14 in a predetermined frequency range, the variation in the gain of the variable gain circuit caused by the variation in the peak value in the frequency characteristics of the speaker 5 and the microphones 6a and 6b is eliminated. An appropriate gain can be set.

[Effect of the Invention] As described above, instead of limiting the volume of the speaker, the present invention is configured to individually control the output signal level of the microphone to a level that does not impair the function of the echo canceling circuit. Even if the microphone is close to the speaker, a sufficient volume of sound can be generated regardless of such acoustic coupling conditions, and the conference can proceed smoothly.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a block diagram showing a configuration of a conventional audio conference apparatus. 1 ... Audio input path, 2 ... Echo canceling circuit, 4,7a, 7b ...
Amplifying circuit, 5 ... Speaker, 6a, 6b ... Microphone,
8 ... addition circuit, 9 ... voice transmission path, 12 ... gain control circuit, 13a, 13b ... gain variable circuit.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Mizuhiro Tobita 1-2356 Take, Yokosuka-shi, Kanagawa Prefecture Within the Combined Communication Research Laboratories of Nippon Telegraph and Telephone Corporation (72) Inventor Naohisa Kushisu 3-1-1 Asahigaoka, Hino-shi, Tokyo No. 1 Toshiba Hino Plant Co., Ltd. (72) Inventor Takashi Saeki 3-1-1 Asahigaoka, Hino City, Tokyo 1 Toshiba Hino Plant Co., Ltd. (72) Inventor Shigenobu Minami 70 Yanagicho, Yuki-ku, Kawasaki City, Kanagawa Prefecture Shares Inside the Toshiba Yanagimachi Plant

Claims (1)

(57) [Claims] 1. A speaker for generating an audible sound from an audio signal transmitted from a conference partner via a line, and a plurality of voices for inputting audio for a conference call and transmitting the audio to the conference partner via the line. A microphone, an echo canceling circuit connected between an audio signal input path to the speaker and an audio signal transmission path of the microphone, and an echo canceling circuit for canceling a loop signal caused by acoustic coupling between the speaker and the microphone; and a predetermined training signal from the speaker. Setting means for detecting the characteristics of the echo canceling circuit by generating the echo canceling circuit, and setting the parameters of the echo canceling circuit in accordance with the detected characteristics. An output side of each of the plurality of microphones And a plurality of variable gain circuits provided in the speaker, and the predetermined training signal is generated from the speaker. If there is a level of the output audio signal from the plurality of microphones that exceeds a predetermined reference value corresponding to a level at which the echo canceling circuit can cancel out the output audio signal from the microphone, A gain control circuit that controls the gain variable circuit so that a signal level is equal to or less than the predetermined reference value.