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JP2006148228

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DESCRIPTION JP2006148228
PROBLEM TO BE SOLVED: To provide a two-way communication system of optimum
characteristics using a pipeline speaker. SOLUTION: In a two-way communication apparatus in
which two or more halls 100 and 200 separated from each other can communicate interactively,
two bodies are arranged at predetermined intervals in each of the halls. The pipeline speaker 11
and the microphone 13 arranged at intervals of 20 cm or more in the longitudinal direction of
the pipeline speaker 11 are provided. [Selected figure] Figure 1
Two-way communication device
[0001]
The present invention relates to a two-way communication device that enables people in two
isolated places to talk interactively.
[0002]
In this two-way communication device, microphones and speakers are respectively installed at
two isolated places, and voices emitted by human beings at one place are received by the
microphones installed at that place and the other places are used. It is made to output this with
the arranged speaker.
Furthermore, in recent years, interactive communication devices with images have been put to
practical use (see, for example, Patent Document 1). At this time, in order to increase the sense of
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reality, it has been proposed to use a plurality of loudspeakers and microphones as an acoustic
device. At this time, by arranging the speakers on substantially the same plane as the image, the
sense of reality can be further enhanced. At this time, it is desirable that the positions of the
microphone and the speaker be close to each other. At this time, when the microphone and the
speaker are disposed in the vicinity, so-called echo or howling may occur due to the
characteristics of both. However, in the two-way communication device, the same person, for
example, while sitting in a chair speaks a voice to a microphone or conversely hears the other
party's voice from a speaker. For this reason, it is desirable to arrange the microphone and the
speaker as close to each other as possible without causing echo or howling.
[0003]
On the other hand, in recent years, as a new type of loudspeaker, a pipeline loudspeaker
configured to emit a sound wave from a linear sound source such that the wave front has a
cylindrical shape has been sold. In a general point sound source, the sound pressure is inversely
proportional to the square of the distance from the point sound source, whereas in a speaker
having such a wavefront, the sound pressure decreases in inverse proportion to the distance
from the sound source. Therefore, there is an advantage that even small sounds can be heard far.
The directivity characteristic of this pipeline speaker is shown in FIG. As shown in FIG. 6A, the
sound pressure is measured along the directions shown in (1) and (2) around the pipeline
speaker 11. The measurement results are shown in FIGS. 6 (b) and 6 (c), respectively. 6 (b) and 6
(c), the directional characteristics of the sound output from the pipeline speaker 11 are displayed
as broken lines at different frequencies. FIG. 6 (b) shows that in the (1) direction, the sound in the
frequency band of 250 to 2 kHz hardly changes in intensity from the center to the edge, but
sharply attenuates in the portion off the edge There is. Further, FIG. 6C shows that the sound in
the band of 250 to 2 kHz has the same sound pressure in almost all directions in the direction
(2).
[0004]
Japanese Patent Application Laid-Open No. 2002-191098
[0005]
However, when the microphone is brought close to the speaker, the sound generated from the
speaker is likely to be received from the microphone, and there is a problem that acoustic
feedback such as echo and howling tends to make it difficult to hear.
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An object of the present invention is to provide an optimal two-way communication device using
a pipeline speaker in view of this point.
[0006]
In order to achieve the above object, the two-way communication device according to the present
invention is a two-way communication device in which two-way communication can be
performed interactively between a plurality of isolated venues It is characterized in that it
comprises a speaker for generating a substantially cylindrical wave sound wave, which is
disposed at a predetermined distance from body to body, and a microphone which is arranged at
a distance of 20 cm or more on the central axis of the cylindrical wave sound wave.
[0007]
According to the present invention, a pipeline speaker is used to obtain a two-way
communication system with optimum characteristics.
Embodiment of the Invention
[0008]
Embodiments of the present invention will be described in detail based on the drawings.
FIG. 1 shows an example in which the two-way communication device according to the present
invention is applied to a TV conference system.
As shown in FIG. 1, in the video conference system of this embodiment, a pipeline speaker 11, a
TV monitor 12, a bi-directional microphone 13, and a TV camera 14 are installed in the
conference room 100 and the opposite conference room 200, respectively. Configured By
connecting the two conference rooms via the communication line 300 and mutually
communicating the images and voices of the conference participants, it is possible to progress
the video conference.
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[0009]
That is, the voice emitted by the conference participant is picked up by the bi-directional
microphone 13 and converted into a digital signal by the information coding unit 15. Also, the
video of the conference participant is captured by the TV camera 14 and similarly converted to a
digital signal by the information encoding unit 15. The audio and video signals converted into
digital signals are transmitted by the transmission / reception control unit 16 to the other
conference room via the communication line 300. Also, the digital audio signal and the digital
video signal transmitted from the other conference room are output to the information decoding
unit 17 via the transmission / reception control unit 16. The information decoding unit 17
converts the digital audio signal and the digital video signal into an analog signal. As a result, the
voice of the conference participant of the other party is output from the pipeline speaker 11, and
the video of the conference participant of the other party is displayed on the TV monitor 12.
[0010]
FIG. 2 shows an arrangement relationship between the pipeline speaker 11 and the bi-directional
microphone 13. As shown in FIG. 2, the two pipeline speakers 11 are arranged vertically at the
floor at a distance D in the horizontal direction. At this time, the axes of the two pipeline speakers
are on the same plane. The distance D is often set to about 100 to 160 cm. It is also desirable
that the two pipeline speakers be at a height close to the height of the caller's face. The two bidirectional microphones 13 are disposed above the pipeline speaker 11 at a distance h. The
distance h is set to 20 cm or more in consideration of the near-field sound from the near-side
pipeline speaker 11 and the directivity of the other pipeline speaker 11. The bi-directional
microphone 13 is disposed on the extension of the axis of the pipeline speaker 11. This is
because the axial direction of the pipeline speaker 11 is the direction in which the sound
radiation is the least. As shown in FIG. 7 ((a) is a side view and (b) is a plan view), the
bidirectional microphone 13 has a direction in which the sensitivity is theoretically zero, and
since it is rotationally symmetrical In fact, it has a low sensitivity surface. This is called the null
plane. The bi-directional microphone 13 is arranged such that the axes of the two pipeline
speakers 11 are included on its null plane.
[0011]
The pipeline speaker 11 has a directional characteristic that the sound pressure in the horizontal
direction with the floor of the conference room 100 is strong, so as long as the wall of the
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conference room is configured vertically, most of the reflected sound of the generated sound is
horizontal Come back. For this reason, not only the sound emitted from the pipeline speaker 11
and directly collected by the bi-directional microphone 13 is extremely small, but also the
reflected sound is hardly collected. Therefore, the probability of occurrence of echo and howling
is extremely small.
[0012]
Next, the characteristics of the system using the pipeline speaker shown in FIGS. 1 and 2 and the
characteristics of the system using the conventional speaker (here, using the YAMAHA NS-10M
sold by the applicant) Compare. FIG. 3 shows a system to be compared, and FIG. 4 shows a graph
as a comparison result. In a system using the pipeline speaker 11, as shown in FIG. 3A, the
horizontal distance D between the pipeline speakers 11 is 100 to 160 cm, and the distance
between the pipeline speaker 11 and the bi-directional microphone 13 is set. Distance h in the
vertical direction is 10, 20 or 40 cm. Further, in a system using a conventional speaker to be
compared, as shown in FIG. 3B, the distance D 'between the speakers 11' is 180 cm, and the
distance D 'between the speakers 11' and the bidirectional microphone 13 is The distance h 'in
the vertical direction is 15 cm.
[0013]
FIG. 4 (a) shows, as a graph, the difference between the characteristics of both systems when D =
160 cm. Similarly, FIG. 4 (b) shows a case where D = 140 cm, FIG. 4 (c) shows a case where D =
120 cm, and FIG. 4 (d) shows a case where D = 100 cm. That is, in the graph of FIG. 4, the
horizontal axis is the center frequency, and the vertical axis is the difference between the
characteristics of both systems. The characteristic difference on the vertical axis is calculated
for the system of FIGS. 3 (a) and 3 (b) when the central frequency is changed in the range of 160
Hz to 10 kHz, and the evaluation value V shown by the following equation is calculated. It is the
meaning of the difference which pulled the evaluation value of [Equation 1] of FIG.3 (b) from the
evaluation value of [Equation 1] of FIG. 3 (a). In both systems, values at 1/3 octave band level are
calculated and used as characteristic values.
[0014]
[Equation 1] V = 10 log 10 (Pave <2> / Gf <2>) where Pave represents the average sound
pressure in the hall where the system is installed, and Gf represents the feedback gain.
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[0015]
The in-field average sound pressure Pave referred to here is measured as follows.
That is, as shown in FIG. 5, a primary sound source s1-s3 for noise generation is arranged in the
room A, and a pair of microphones Mic is arranged. The arrangement relationship can be, for
example, as shown in FIG. 5, but this is merely an example. Further, in another room B, a pipeline
speaker 11 for reproducing a signal collected by this microphone is disposed. The noise
generated from the primary sound source s1 is collected by the microphone Mic, and the
collected sound is reproduced from the pipeline speaker PLS. The sound pressure at each point
of p1-p6 in the room B at this time is measured. The noise is similarly reproduced from the
primary sound sources s2 and s3 of the room A, and the sound pressure is similarly measured.
The average value of the sound pressure data of s1-s3 is set as the above-described in-field
average sound pressure Pave. Further, the feedback gain Gf is a gain when the sound emitted
from the pipeline speaker PLS is collected by the microphone Mic disposed on the axis of the
pipeline speaker PLS.
[0016]
As apparent from FIGS. 4 (a) to 4 (d), when h = 10 cm or less, the characteristics are inferior or
comparable to those of the conventional system, particularly in the low frequency region, but h =
20 cm In the case of 40 cm, regardless of the size of D, the system according to the present
embodiment (FIG. 3 (a)) is higher than the conventional system (FIG. 3 (b)) in almost all areas. It
can be seen that the characteristics are shown. Overall, an open loop gain improvement of
approximately 6 dB is obtained compared to conventional systems.
[0017]
Although the embodiment has been described above, the present invention is not limited to the
two-channel type as in the above-described embodiment, and may be a single channel.
[0018]
The whole structure of the video conference system which concerns on this Embodiment is
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shown.
The positional relationship of the pipeline speaker 11 and bi-directional microphone 13 of the
video conference system of FIG. 1 is shown. It is a comparison figure of the video conference
system shown in FIG. 1, and the conventional video conference system. It is the graph which
compared the characteristic of the video conference system shown in FIG. 1, and the
conventional video conference system. An example of the measuring method of the in-field
average sound pressure Pave is shown. An example of the directivity characteristic of the
pipeline speaker 11 is shown. An example of the characteristic of bi-directional microphone 13 is
shown.
Explanation of sign
[0019]
100, 200 ... conference room, 300 ... communication line, 11 ... pipeline speaker, 12 ... TV
monitor, 13 ... bi-directional microphone, 14 ... TV camera, 15 ... information coding unit, 16 ...
transmission / reception control unit, 17 ... Information decryption unit.
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