JP4501563B2 - Audio apparatus and remote conference system - Google Patents

Description

  The present invention relates to an audio device that is integrally provided with a speaker and a microphone and that cancels the wraparound of sound from the speaker to the microphone, and a remote conference system that uses this audio device.

  Various remote conferencing systems have been proposed for performing remote conferences by connecting audio conference rooms between remote conference rooms. In the remote conference system, each conference room is provided with a microphone for collecting the speech of the conference attendee and a speaker for emitting the voice of the other party conference room. As an installation form of the microphone and speaker, a form in which a microphone for each attendee is provided, a form in which a microphone for the entire conference room is provided, a form in which a speaker or earphone for each attendee is provided, and a form in which a speaker for the entire conference room is provided Various forms are conceivable.

  Among these, the configuration in which microphones and speakers for the entire conference room as shown in Patent Document 1 are not required to match the number of conference attendees as in the case of each device, or each device Since the number of conference attendees is not limited by the number of conferences, the degree of freedom is high and the installation is easy, which is advantageous in terms of cost.

  In addition, there is a sense of presence as a conference, and when linked with video in a video conference, audio can be generated from the direction of the video and speech can be made in that direction, making it possible to hold a remote conference in a natural atmosphere There are advantages.

  However, since the speaker emits sound to the entire conference room and the microphone collects sound from the entire conference room, a loop occurs in which the sound emitted from the speaker is collected again by the microphone. However, there is a problem that howling that oscillates completely different from the voice of the utterance is generated and unnecessary reverberation occurs in the voice of the utterance or an echo that can be heard repeatedly occurs.

Conventionally, in order to eliminate such howling and echo, a digital processing unit is provided in the audio circuit, and a sound that circulates from a speaker to a microphone is simulated and canceled to cancel the howling and echo. It has been proposed (for example, Patent Document 2).
JP-A-10-136100 Japanese Patent Laid-Open No. 05-063609

  However, the above-described echo cancellation apparatus using digital processing has a drawback that the circuit configuration is complicated and it is difficult to set a simulation model (parameter) in accordance with the installation conditions of the speaker and microphone.

  It is an object of the present invention to provide an audio device capable of canceling howling and echo with a simple configuration without providing a complicated and high-performance digital processing device, and a remote conference system using the audio device. .

The invention according to claim 1 is provided symmetrically with respect to the boundary surface , with acoustic output means for forming sound waves having phases opposite to each other in the front surface direction and the rear surface direction of the boundary surface with one plane as the boundary surface , A front microphone that picks up sound waves formed in the front direction, a rear microphone that picks up sound waves formed in the rear direction, and a signal that synthesizes and outputs a signal collected by the front microphone and a signal picked up by the rear microphone And a synthesizing means.
The invention according to claim 2 is characterized in that an acoustic impervious layer is provided on a boundary surface between the front microphone and the rear microphone.

  Sound waves formed in the front direction by the sound output means are collected around the front microphone, and sound waves (opposite phase) formed in the rear direction are collected around the rear microphone. Therefore, the output signal of the signal synthesizing means for synthesizing and outputting the signal collected by the front microphone and the signal collected by the rear microphone is a signal in which the wraparound sound is canceled. On the other hand, since the voice of the conference attendant comes from one direction (front direction), only the microphone provided in the one direction picks up the sound and is output without being canceled even if synthesized. .

According to a third aspect of the present invention, the sound output means is constituted by a flat speaker, the front microphone, the rear microphone, and the sound impervious layer are constituted by a flat microphone unit, and the flat speaker and the microphone unit are combined in a panel shape. It is characterized by.

  By combining the sound output means and the microphone unit in the form of a panel as described above, the sound device including the microphone and the sound output means (speaker) can be configured to be movable like a whiteboard, for example. If this panel is made of white, it can be used as a screen for a projection television, and can also be used for a video conference system.

The invention according to claim 4 is characterized in that the sound output means is composed of a planar condenser speaker having a planar diaphragm, and the front microphone and the rear microphone are composed of a planar condenser microphone having a planar diaphragm. And

  Since the planar capacitor microphone is symmetrical in the front-rear direction, it outputs sound waves having the same waveform in the front direction and the rear direction with the phases reversed. Further, since the vibration is a surface vibration, directivity in the front direction is present, and there is little wraparound to the microphone that is installed beside it.

According to a fifth aspect of the present invention, the planar speaker is composed of two layers of a front side planar speaker and a rear side planar speaker, and the planar diaphragm of the front side planar speaker is a planar diaphragm of a front microphone. And the rear side flat speaker is arranged such that the flat diaphragm of the rear flat speaker is flush with the flat diaphragm of the rear microphone.

  In the present invention, since the planar speaker is made of two layers, the vibration of the rear planar speaker excites the diaphragm of the front planar speaker, and the sound pressure level can be doubled. In addition, since the front side planar speaker and the rear side planar speaker are directly beside the front microphone and the rear microphone, respectively, speaker sound wraparound is minimized.

A sixth aspect of the present invention is the signal processing apparatus according to any one of the first to fifth aspects, wherein the signal synthesizing means is at least one of a signal collected by the front microphone and a signal collected by the rear microphone. Signal processing means for adjusting the level or frequency characteristic of the signal.

According to a seventh aspect of the present invention, there is provided a remote conference system in which the acoustic device according to any one of the first to sixth aspects is installed in each of a plurality of rooms, and the output signal of the signal synthesizing means of each of the acoustic devices is other than that. It is connected so that it may input into the audio | voice output means of the audio equipment of this.

  In the present invention, two or more audio devices are installed in separate conference rooms and connected to each other. The connection form is a form in which the output signal of the signal synthesizing means of each acoustic device is connected to the sound output means of another acoustic device via the transmission means. When configured with three or more acoustic devices, the output of the signal synthesizing means of one acoustic device is commonly connected to the sound output means of the other two or more acoustic devices. As a result, howling and echo are canceled in each device, and a smooth remote conference is possible.

  The transmission means may be any device such as an audio cable, a local area network, a telephone line, the Internet, radio wave communication, infrared communication.

  According to the present invention, in order to give a sense of realism in the conference, the sound of the other party is emitted to the entire room, and this sound wraps around the microphone for speech collection to generate howling and echo. This makes it possible to realize a remote conference with a sense of reality.

  FIG. 1 is a diagram showing a schematic configuration of a panel type acoustic apparatus 1 according to an embodiment of the present invention. (A) is a front view (viewed from the front), and (B) and (C) are plan views (viewed from the top) of different embodiments.

  As shown in FIG. 4 and FIG. 6, this panel type acoustic apparatus 1 is used for a remote conference system, and is installed in each of a plurality of conference rooms.

  This panel type acoustic device 1 is obtained by integrally joining a microphone unit 10 having two front and rear planar condenser microphones (front microphone 11F and rear microphone 11R) and a planar speaker 12 in a panel shape. Thus, it is preferable to configure as a self-supporting apparatus. The number and shape of the microphone units 10 and the number and shape of the planar speakers 12 are not limited to those shown in this figure.

  In this embodiment, a capacitor speaker is used as the planar speaker. However, any configuration may be used as long as the same signal is output to the front and rear surfaces in opposite phases.

  As shown in FIGS. 2B and 2C, the microphone unit 10 includes a front microphone 11F that is a flat condenser microphone provided toward the front surface and a rear condenser microphone that is provided toward the rear surface. The microphone 11R is composed of an acoustically opaque layer 13 for blocking sound propagation between the front microphone 11F and the rear microphone 11R, and the acoustic microphone 13 is sandwiched between the front microphone 11F and the rear microphone 11R. Are arranged back to back. The sound impervious layer 13 may be made of a sound absorbing material such as urethane or a rigid body such as a steel plate. The center of the sound impervious layer 13 serves as a front / rear boundary line (front / rear boundary surface) of the panel acoustic device 1.

  On the other hand, the planar speaker 12 may be provided in a single layer so that the diaphragm is aligned with the front and rear boundary surfaces of the panel as shown in FIG. 5B. As shown in FIG. A flat speaker may be provided in two layers on the front side and the rear side so that the surface of the diaphragm coincides with the diaphragm of 11F and the rear microphone 11R (so as to be in the same plane). A space is provided between the two-layer flat speakers so that sound can be transmitted.

FIG. 2 is a diagram illustrating the configuration of the microphone unit 10 and the planar speaker 12 and the audio signals collected by the front microphone 11F and the rear microphone 11R.
In the figure, a front microphone 11F and a rear microphone 11R are planar condenser microphones, and a diaphragm 42 made of a conductive thin film without air permeability is provided between two mesh-like fixed electrodes 40, 41. A bias voltage is applied to the diaphragm 42. The diaphragm 42 and the fixed electrodes 40 and 41 are electrostatically coupled, and the fixed electrodes 40 and 41 have a capacitance according to the distance from the diaphragm 42 by a bias voltage applied to the diaphragm 42. Has occurred. When a sound wave comes from the outside, the vibration plate 42 vibrates by the sound wave, and the distance between the vibration plate 42 and the fixed electrodes 40 and 41 is changed by this vibration. A minute current is generated due to the change, and a signal voltage obtained by flowing the minute current through a resistance element having a high resistance value is amplified by a differential amplifier, whereby an incoming sound wave can be extracted as a sound signal. .

  The flat speaker 12 is a flat capacitor speaker, and a diaphragm 52 made of a conductive thin film having no air permeability is provided between two mesh-like fixed electrodes (positive electrode and negative electrode) 50 and 51, and the diaphragm is provided on the diaphragm. By applying a bias voltage and applying an audio signal voltage to the fixed electrode, the diaphragm 52 is vibrated to output an audio signal as sound. Since the front surface and the rear surface of the flat diaphragm 52 are opened through the mesh electrodes 50 and 51 in the same manner, a sound wave having a positive phase is formed and output in the front direction, and a sound in the opposite phase is generated in the rear direction. A wave is formed and output under the same amplitude and frequency characteristics as the front surface.

  Since the planar speaker 12 forms an audio wave by the vibration of the planar diaphragm 52, the formed audio wave becomes a plane wave and has directivity in the front direction. Accordingly, it is possible to reduce the wraparound of the sound to the microphone unit 10 provided almost beside.

  Further, as shown in FIG. 1C, the planar speaker 12 is made up of two layers of a front side speaker 12F and a rear side speaker 12R, thereby doubling the sound pressure of the output sound wave and generating a loud sound. In addition to being able to occur, it is possible to minimize the wraparound of the sound with respect to the adjacent planar condenser microphones 11F and 11R. In other words, the sound wave generated by the front-side flat speaker 12F wraps around the front microphone 11F, but the front microphone 11F and the front-side speaker 12F are arranged in a lateral relationship where the diaphragm is on the same plane. Therefore, the front microphone 11F is arranged at a position where the directivity of the sound wave generated by the front speaker 12F is the weakest, and the sound wraps around the front microphone 11F is minimized. Note that the sound generated by the rear speaker 12R on the front side excites the diaphragm of the front speaker 12F to increase the acoustic energy, but the sound wave generated by the rear speaker 12R is directly directed diagonally to the front microphone 11F. I won't go around. The rear microphone 11R and the rear speaker 12R are the same as the front microphone 11F and the front speaker 12F.

  In FIG. 2, the positive phase sound wave (speaker sound) formed on the front surface by the flat speaker 12 is transmitted in the front direction and collected as a wraparound sound by the front microphone 11F. On the other hand, the reverse phase audio signal (speaker audio) formed on the rear surface by the flat speaker 12 is transmitted in the rear direction and collected as a wraparound sound by the rear microphone 11R.

  When sound signals generated by vibrations of the diaphragm of the same planar speaker 12 are picked up by two microphones 11F and 11R arranged in a symmetrical positional relationship with respect to the front and rear boundary surfaces, these signal waveforms are almost in reverse phase. It can be said that the signal waveforms cancel each other. A factor that hinders the symmetry of the waveform is that the spatial shape is different between the front side and the rear side of the installation location of the panel type acoustic apparatus 1. Therefore, by adding and synthesizing the output signal of the front microphone 11F and the output signal of the rear microphone 11R, the wraparound sound of the flat speaker 12 can be canceled.

  On the other hand, the panel type acoustic device 1 is generally installed near the wall of a conference room, and the voice of the speaker (conference attendee) reaches only from the front direction and is collected only by the front microphone 11F. (Because there is the acoustic impervious layer 13, it does not reach the rear microphone 11R). Therefore, the speaker's voice and the normal phase speaker sound are collected into the front microphone 11F, and only the reverse phase speaker sound is input into the rear microphone 11R.

  Therefore, if the output signal of the front microphone 11F and the output signal of the rear microphone 11R are added and synthesized, the speaker sound picked up by the two microphones in the opposite phase is canceled, and the sound from the speaker is substantially circulated. As a result, only the voice of the speaker is taken out.

  Since the wraparound sound from the speaker is canceled and disappears, the signal loop of the microphone → speaker → microphone is cut, and howling and echo do not occur.

  As described above, there is a slight difference in signal level and frequency characteristics between the speaker sound picked up by the front microphone 11F and the speaker sound picked up by the rear microphone 11R due to the difference in the space shape between the front side and the rear side. There is a case. Even in this case, the speaker sound is attenuated to a sufficiently low level, so that it does not oscillate and cause howling or an echo that may be of interest to the conference participants, but the speaker sound is not completely canceled. For this reason, in the panel type acoustic device 1 of this embodiment, an equalizer 15 is further connected to each microphone 11 in order to completely cancel the remaining speaker sound.

  FIG. 3 is a diagram for explaining an electric circuit of the panel acoustic device 1. Equalizers 15F and 15R are connected to the front microphone 11F and the rear microphone 11R, respectively. The equalizer 15R connected to the rear microphone 11R is a circuit for correcting the frequency characteristics and the level so that the speaker sound waveform output from the rear microphone 11R completely matches the speaker sound output from the front microphone 11F.

  Further, the equalizer 15F connected to the output side of the front microphone 11F is for improving the sound quality of the voice signal obtained by collecting the voice of the speaker. The equalizer 15R corrects the level and frequency characteristics so that the speaker sound picked up by the rear microphone 11R becomes the same signal (in reverse phase) as the speaker sound of the front microphone 11F that has passed through the equalizer 15F.

  In FIG. 3, the output signals of the front microphone 11F and the rear microphone 11R output from the equalizers 15F and 15R are added and synthesized by the adder circuit 16, and then output to the counterpart device via the output terminal 17. In this embodiment, the equalizers 15F and 15R and the adder circuit 16 constitute the signal synthesis circuit 20. However, when the configuration is simplified, the equalizers 15F and 15R are not necessary, and a volume for adjusting the level. It may be only.

  In addition, audio signals from the counterpart device are input to the two planar speakers 12 via the input terminal 18 and the voltage amplifier 21. Note that the audio signals input to the two planar speakers shown in the figure may not be the same signal. That is, it may be a signal sent from a separate panel type acoustic device 1 or a signal collected by different microphone units of the same panel type acoustic device 1.

  FIG. 4 is a diagram showing an example of electrical connection in a remote conference system using two panel type acoustic devices 1. In this figure, in order to simplify the description, the equalizers 15F and 15R shown in FIG. 3 are not shown. One panel type acoustic device 1 </ b> A is installed in a conference room A. The other panel type acoustic apparatus 1B is installed in the conference room B. Hereinafter, the panel type acoustic apparatus 1A will be described. A common bias voltage is applied to the diaphragms 42F and 42R of the front microphone 11F and the rear microphone 11R, and the fixed electrodes 40F and 40R on the sound collection side are commonly connected to the non-inverting input terminal of the differential amplifier 30. ing. Further, the fixed electrodes 41 </ b> F and 41 </ b> R on the acoustic opaque layer 13 side are commonly connected to the inverting input terminal of the differential amplifier 30. By connecting the fixed electrodes 40F and 40R and the fixed electrodes 41F and 41R to the terminal of the differential amplifier 30 in common, the signals of both the front and rear microphones 11F and 11R are added and synthesized, and circulated from the planar speaker 12 Speaker sound is canceled. The differential amplifier 30 outputs only the voice signal of the speaker picked up by the front microphone 11F. This audio signal is supplied to the flat speaker in the conference room B through a predetermined transmission means.

  On the other hand, the speaker speaker in the conference room B is supplied to the condenser speaker 12 in the conference room A from the differential amplifier 30 in the conference room B. The supplied audio signal is amplified by the voltage amplifier 31P and applied to the fixed electrode 50 on the front surface side of the planar speaker (condenser speaker) 12, and the inverted voltage amplifier 31M amplifies the phase by inverting the polarity. It is applied to the fixed electrode 51 on the rear surface side of the flat speaker 12. A bias voltage is applied to the diaphragm 52, which vibrates due to an attractive force and a repulsive force corresponding to a potential difference from the fixed electrodes 50 and 51, and generates an air vibration that becomes a sound wave. When the diaphragm 52 vibrates to the front side and forms a dense wave on the front side, a sparse wave is formed on the back side, and conversely, the diaphragm 52 vibrates to the rear side and generates a sparse wave on the front side. When formed, a dense wave is formed on the back side, so that the sound wave output to the front side and the sound wave output to the back side have opposite phases.

  The positive phase speaker sound output to the front side wraps around and is collected by the front microphone 11F, and the reverse phase speaker sound output to the rear side wraps around the rear microphone 11R and is collected. The voice is canceled by adding and synthesizing.

  FIG. 5 is a diagram showing a panel type acoustic device for a video conference system in which a large number of planar speakers and microphone sets are combined. This panel type acoustic device also serves as the screen 2 of the projector TV, and is used together with the TV camera 3 when performing a video conference by connecting a plurality of conference rooms separated from each other as shown in FIG.

  The panel type acoustic apparatus 1 shown in FIG. 1 has a two-stage configuration of speakers and microphones, and the upper stage has four substantially square planar speakers 12 arranged side by side, and a vertically rectangular microphone between each planar speaker 12. Unit 10 is arranged. In the lower stage, three substantially square planar speakers 12 are arranged side by side, and further, planar speakers 12 having a substantially half horizontal width are arranged at both ends, and between each of the planar speakers 12, a vertically rectangular microphone unit is provided. 10 is arranged.

  By using this panel type acoustic device 1 as the screen 2 (or as part of the screen 2) and projecting the video of the other party's conference room, the sound can be heard from the direction in which the video of the conference room is shown. Since it is necessary to speak toward the microphone unit 10 (front microphone 11F) in that direction, a remote conference is performed with a natural posture and atmosphere rather than speaking toward an individual microphone. Is possible.

  Note that the remote conference system (video conference system) is not limited to a form in which the two panel-type acoustic devices 1 are connected one-to-one. Three or more panel-type acoustic devices 1 may be connected in a star shape or a diagonal shape. The transmission method of the audio signal between the panel type acoustic devices is arbitrary. A plurality of transmission methods can be mixed.

  The microphone is not limited to a planar condenser microphone. A normal dynamic microphone may be used. In this case, the directivity in the lateral direction may be blocked by storing in a cylindrical case.

  Further, as a configuration similar to that shown in FIG. 1C, the front speaker 12F and the rear speaker 12R are not limited to planar speakers, and may be ordinary cone speakers. In this case, the audio signal input to the front speaker and the audio signal input to the rear speaker invert the phase of the audio wave formed by inverting the terminals. In the case of a cone speaker, it is housed in a speaker box, but the speaker box may be common on the front side and the rear side, or may be separate. Further, the speakers may be one each on the front side and the rear side, or may be a plurality of small speakers arranged.

The figure which shows schematic structure of the panel type acoustic apparatus which is embodiment of this invention The figure explaining the structure of a capacitor | condenser microphone and a capacitor | condenser speaker and the wraparound of a speaker signal The figure explaining the electric circuit of the panel type acoustic device The figure which shows the example of the electrical connection in the teleconference system using two panel type | mold audio apparatuses The figure which shows the panel-type audio apparatus for video conference systems which combined many planar speakers and microphone sets The figure explaining the installation form of the panel type acoustic apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Panel type acoustic apparatus 10 ... Microphone unit 11F ... Front microphone (planar condenser microphone)
11R: Rear microphone (planar condenser microphone)
12 ... Planar speaker (12F ... front side speaker, 12R ... rear side speaker)
DESCRIPTION OF SYMBOLS 13 ... Sound opaque layer 15F, 15R ... Equalizer 16 ... Adder circuit 17 ... Signal output terminal 18 ... Signal input terminal 20 ... Signal composition circuit 21 ... Voltage amplifier 30 ... Differential amplifier 31P ... Voltage amplifier 31M ... Inverting voltage amplifier 40, 41 ... Fixed electrode 42 (for a planar condenser microphone) ... Vibrating plates 50, 51 (for a planar condenser microphone) ... Fixed electrode 52 (for a planar loudspeaker) ...

Claims (7)

Acoustic output means for forming sound waves having phases opposite to each other in a front surface direction and a rear surface direction of the boundary surface using one plane as a boundary surface ;
A front microphone that is installed symmetrically with respect to the boundary surface and collects sound waves formed in the front direction; a rear microphone that collects sound waves formed in the rear surface direction;
Signal synthesis means for synthesizing and outputting the signal picked up by the front microphone and the signal picked up by the rear microphone;
A sound device comprising:   The acoustic apparatus according to claim 1, wherein an acoustic impervious layer is provided on a boundary surface between the front microphone and the rear microphone. The sound output means is composed of a flat speaker,
The front microphone, the rear microphone, and the sound impervious layer are configured with a planar microphone unit,
The acoustic apparatus according to claim 2, wherein the planar speaker and the microphone unit are combined in a panel shape. 4. The acoustic apparatus according to claim 3 , wherein the acoustic output means is configured by a planar capacitor speaker having a planar diaphragm, and the front microphone and the rear microphone are configured by a planar capacitor microphone having a planar diaphragm. The flat speaker is composed of two layers of a front side flat speaker and a rear side flat speaker,
The front-side flat speaker is arranged so that the flat diaphragm of the front-side flat speaker is flush with the flat diaphragm of the front microphone, the rear-side flat speaker is arranged, and the flat diaphragm of the rear-side flat speaker is the rear microphone. The acoustic device according to claim 4 , wherein the acoustic device is arranged so as to be flush with a flat diaphragm. It said signal combining means, one of said signals front microphone picked up, rear claims 1 to 5 with a signal processing unit microphone to adjust the level or frequency characteristic of the at least one signal of the picked-up signal acoustic device according to any. The acoustic device according to any one of claims 1 to 6 is installed in each of a plurality of rooms, and connected to input an output signal of a signal synthesizing unit of each acoustic device to an audio output unit of another acoustic device. A remote conference system.

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