JPS6337703A - Mixing circuit - Google Patents

Abstract

PURPOSE:To output a mixing signal from which an articulate reproduction sound is obtained by mixing sound signals obtained from plural microphones while emphasizing signals which are relatively high in level. CONSTITUTION:A sound generated to a microphone 1-1 is inputted to the microphone 1-1 as shown by a broken-line arrow A1 and also inputted to other microphones 1-2 and 1-n shown by broken-line arrows A2 and An. At this time, sound signals generated by the microphones 1-2 and 1-n are lower in level than the sound generated by the microphone 1-1. The level difference between the former and latter increases by the expansion ration of expanders 2-1 and 1-n behind the expanders 2-1 and 2-n. Consequently, the component of the sound signal generated by the microphone 1-1 is emphasized in the sent signal of an amplifier 3, and the signal is amplified by a compressor 4 while the level difference is held emphasized. Consequently, the mixing signal from which the articulate reproduction sound is obtained is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a mixing circuit, and particularly to a mixing circuit for adding and amplifying audio signals emitted from a plurality of microphones in an audio conferencing system or the like.

[Conventional technology]

Mixing circuits used in conventional audio conferencing systems amplify and add the audio signals emitted from multiple microphones, mix the multiple audio signals, and output a single mixed signal. [Problems to be Solved by the Invention] With the above-mentioned conventional mixing circuit, when mixing audio signals emitted from multiple microphones placed on a conference table, as in the case of an audio conference system, for example, when a certain microphone The sound emitted towards the other microphones is also crowded, and the arrival time of the sound from each microphone is different from each other, so the sound reproduced from the mixed signal by the speaker may be unclear and contain multiple reverberations. There is a problem that it becomes difficult to listen.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an object of the present invention is to provide a mixing method in which clear reproduced sound can be obtained by emphasizing and mixing relatively high-level audio signals emitted from a plurality of microphones. [Means for Solving the Problems] The circuit of the present invention receives a plurality of audio signals emitted from a plurality of microphones and outputs a signal from each of the audio signals. A plurality of expanders that detect the level and amplify the audio signal with a gain determined in accordance with the level change to expand the level change of the audio signal, and an adder that adds and sends out signals from the multiple expanders. and one compressor having a level characteristic such that the sum of gains with each of the expanders becomes a predetermined round value, and compressing level changes in the signal sent out by the adding means.

〔Example〕

Next, one embodiment of the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a level characteristic diagram for explaining its operation.

In FIG. 1, a plurality of microphones 1-1 to l-
The audio signals emitted from n are sent to decompressors 2-1 to 2-n, respectively. Each of the expanders 2-1 to 2-n is a syllabic expander having the same level characteristics, for example, a level characteristic of characteristic E shown by a solid line in FIG. Characteristic E means that the average level (input level) of the input signal is L.
Between m (dBr) and LM (dBr), the gain increment changes in proportion to the input level increment, and when the input level is below Lm (dBr) or above Ly (dBr), the gain changes accordingly. is constant. Each stretcher 2-1
to 2-n are microphones 1-1 to 1, respectively.
- detect the average level of the audio signal sent from n,
The audio signal is amplified with a gain determined by the characteristic E according to the detection result and sent to the amplifier 3. The amplifier 3 is a summing amplifier, which adds and amplifies the audio signals sent from the expanders 2-1 to 2-n, and sends the amplified signals to the compressor 4. The compressor 4 is
It is a syllabic compressor that has level characteristics such that the gain sum with each expander 2-1 to 2-n becomes a predetermined constant value, detects its own output level, and responds according to the detection result. The signal amplified with a gain determined by

In this embodiment, for example, the sound emitted toward the microphone 1-1 is transmitted to the microphone 1-1 as shown by the broken line arrow A1.
At the same time, it also enters other microphones 1-2 to l-n as shown by broken line arrows A2 to An. At this time, the audio signals emitted from the microphones 1-2 to ln have a lower level than the audio signal emitted from the microphone 1-1. The level difference between the former and the latter, after passing through the expanders 2-1 to 2-n, is
increases by a stretch ratio of n. For example, when the stretch ratio is 2, that is, in Fig. 2, the human curve is (Lo+fl
) (LBr) (However, Lm ((Lo-f-j! ) <
When the gain is (no-
H) (dB), each level difference between the audio signal emitted by microphone 1-1 and the audio signal emitted by microphones 1-2 to l-n increases by two times after expansion (however, The average level of each audio signal is Lm - LM
(dBr)).

As a result, the output signal from amplifier 3 is
The component of the audio signal emitted from the audio signal 1 is emphasized, and the compressor 4 amplifies it to i while maintaining the emphasis of this level difference. Therefore, the arrangement interval of microphones 1-1 to l-H,
By selecting appropriate values for the expansion characteristics of the expanders 2-1 to 2-n, the highest level of the audio signals emitted from the microphones 1-1 to 1-n is emphasized.
It is possible to obtain a mixing signal that relatively suppresses other signals and provides clear reproduced sound.

〔Effect of the invention〕

As explained above, in the present invention, it is possible to obtain clear reproduced sound by emphasizing and mixing relatively high-level audio signals emitted from a plurality of microphones. This has the effect of realizing a mixing circuit that outputs such a mixing signal.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are a block diagram showing one embodiment of the present invention and a characteristic diagram for explaining its operation, respectively. 1-1~1-n...Microphone, 2-1~2
- n...Extender, 3...Amplifier, 4
・・・・・・Compressor. Agent Patent Attorney Susumu Uchihara /-yz vEI/ Zuhaku Z Closed

Claims (2)

[Claims] (1) Receive multiple audio signals emitted from multiple microphones, detect the level of each audio signal, amplify the audio signal with a gain determined according to the level, and change the level of the audio signal. , a plurality of decompressors for decompressing a plurality of decompressors, an adding means for adding and transmitting signals sent from the plurality of decompressors, and a compressor for compressing a level change in a signal sent from the adding means. Characteristic mixing circuit. (2) The compressor and the compressor of the mixing circuit have a level characteristic such that the sum of respective gains always becomes a predetermined constant value in the compressor and the expander. The mixing circuit described in section 1).