JP2000253134

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DESCRIPTION JP2000253134
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
hands-free device capable of making calls with the other party without using a handset, and in
particular, it spreads in the horizontal direction the sound output from the speakers and makes
calls with surrounding speakers. The present invention relates to a hands-free communication
device that makes it possible.
[0002]
2. Description of the Related Art FIG. 13 is a block diagram of a conventional hands-free
communication device disclosed in, for example, Japanese Patent Laid-Open No. 3-278800. FIG.
14 is a circuit diagram of the hands-free communication device shown in FIG. In the figure, 1 is a
housing, 13 is a first speaker, 14 is a second speaker, 3a is a conversion circuit, 15 is a
microphone, 5 is a transmission / reception circuit, 6 is a transmission signal, 7 is a reception
signal, 8 is this handsfree It is a speaker who talks with the other party (not shown) using a
calling device. Reference numerals 40 and 41 denote A / D converters, 42 to 44 D / A converters,
45 an adaptive filter, 46 a delay circuit, 51 a reverse phase amplifier, and 9a and 9b amplifiers.
[0003]
Next, the operation will be described with reference to FIGS. 13 and 14. The microphone 15
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converts the own speech spoken by the speaker 8 into an analog transmission signal, and the
amplifier 9 b amplifies and outputs the signal to the A / D converter 41. The A / D converter 41
converts the input analog transmission signal into a digital transmission signal and outputs the
digital transmission signal to the D / A converter 44. The D / A converter 44 converts the input
digital transmission signal into an analog transmission signal and outputs it to the transmission /
reception circuit 5. The transmission / reception circuit 5 outputs the input analog transmission
signal as the transmission signal 6 to the other party.
[0004]
The transmission / reception circuit 5 also outputs an analog reception signal 7 input from the
other party to the A / D converter 40. The A / D converter 40 converts an analog reception signal
into a digital reception signal, and outputs the signal to the D / A converter 42 or the D / A
converter 43 through the adaptive filter 45 or the delay circuit 46. The operations of the
adaptive filter 45 and the delay circuit 46 will be described later. The D / A converter 42
converts the digital reception signal into an analog reception signal and outputs it to the reverse
phase amplifier 51. Further, the D / A converter 43 converts the digital reception signal into an
analog reception signal and outputs the signal to the amplifier 9a.
[0005]
The amplifier 9 a amplifies the input analog reception signal and outputs the amplified signal to
the first speaker 13. In addition, the reverse phase amplifier 51 amplifies the input analog
reception signal and outputs it to the second speaker 14 in reverse phase. As a result, the other
party's voice is output from the first speaker 13, and the other party's voice of the opposite
phase is output from the second speaker 14. As a result, the amount of wrap around the other
party's voice from the first speaker 13 into the microphone 15 is offset by the opposite phase
voice from the second speaker 14, so that the other party's voice input to the microphone 15 is
blocked. And echo, howling, etc. can be prevented.
[0006]
Next, the operation of the adaptive filter 45 and the delay circuit 46 will be described. For
example, when the distance to the microphone 15 is the same for both the first speaker 13 and
the second speaker 14, to the microphone 15 of the other party voice output by the first speaker
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13 and the opposite voice of the opposite phase output by the second speaker 14 Since the
phase shift does not occur because the arrival times of the two are equal, the opposite voice at
the position of the microphone 15 is offset. However, when the distance between the first
speaker 13 and the second speaker 14 to the microphone 15 is different, the other-party voice
output from the first speaker 13 and the opposite-phase voice output from the second speaker
14 to the microphone 15 Since the arrival times are different, the phase at the position of the
microphone 15 may be shifted and not canceled.
[0007]
The adaptive filter 45 is provided to cope with the above phenomenon, and takes the form of a
transversal filter used in an echo canceller, a line equalizer, etc., and the digital transmission
output from the A / D converter 41. The other party's voice which has not been canceled out is
detected from the speech signal, and the phase of the digital reception signal output from the A /
D converter 40 is delayed. As a result, the phases of the opposite side audio output from the first
speaker 13 and the opposite side audio output from the second speaker 14 are completely
opposite in phase to each other at the position of the microphone 15. The other party's voice is
more offset.
[0008]
Further, the delay circuit 46 is provided corresponding to the case where the distance between
the first speaker 13 and the microphone 15 is longer than the distance between the second
speaker 14 and the microphone 15, and half of the delay capacity of the adaptive filter 45 Is a
circuit having a delay capacity of For example, if the adaptive filter 45 has a delay capacity of 40
msec, the delay circuit 46 has a delay capacity of 20 msec.
[0009]
FIG. 15 is an output characteristic diagram at the position of the speaker 8 in the hands-free
communication device shown in FIG. 13. The horizontal axis shows frequency (Hz) and the
vertical axis shows sound pressure level (dB). Further, G1 represents respective output
characteristics of the other party voice output by the first speaker 13 and the opposite party
voice output by the second speaker 14 at the position of the speaker 8, and the G2 is output by
the first speaker 13 It is a synthetic ¦ combination output characteristic in the position of the
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speaker 8 of the other party side voice and the other party side voice which the 2nd speaker 14
outputs.
[0010]
Looking at G2 in FIG. 15, in the low band where the wavelength is long and the influence of the
phase delay is small, it is substantially canceled by the opposite voice output from the first
speaker 13 and the opposite voice output from the second speaker 14 in opposite phase.
Because the sound pressure is smaller. Further, in a high frequency band where the wavelength
is short and the influence of phase delay is large, a band that is synergistic with a band canceled
by the opposite side voice output from the first speaker 13 and the opposite phase voice output
from the second speaker 14 The sound pressure becomes uneven because of the alternating
occurrence.
[0011]
SUMMARY OF THE INVENTION The conventional hands-free communication device is
configured as described above, and has the following problems. (1) In the conventional handsfree communication device, the position of the speaker 8 at the time of use is limited to the front
of the first speaker 13 and the second speaker 14 as shown in FIG. When the hands-free
communication device shown in FIG. 6 is arranged, only the voice of the speaker facing the
microphone 15 can be picked up among the speakers surrounding the round table, and the other
voice is equally output to a plurality of speakers There was a problem that it was impossible.
[0012]
(2) In the conventional hands-free communication device, the other party's voice at the position
of the speaker 8 is as shown by G2 in FIG. 15, and the clarity of the other party's voice at the
speaker 8's position is low. There was a problem that it was difficult for them to hear.
[0013]
(3) There is a problem that the circuit becomes complicated due to the use of two speakers and
the cost increases.
[0014]
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The present invention has been made to solve the problems as described above, and its first
object is to provide a hands-free talk apparatus for a conference which can be used by a plurality
of speakers surrounding, for example, a round table. It is a thing.
The second object of the present invention is to provide a hands-free communication device in
which the other party's voice can be easily heard at the position of the speaker.
The third object is to provide a hands-free communication device with a simple configuration by
using a single speaker.
[0015]
A hands-free communication device according to the present invention comprises a housing, a
speaker provided on the top surface of the housing and outputting the other party's voice
vertically upward, and the speaker facing the speaker. And a reflector for reflecting the other
party's voice output from the speaker to convert the output direction, and a microphone provided
on the top surface of the reflector for inputting voice from the speaker.
[0016]
In the hands-free communication device according to the next invention, a bi-directional
microphone is used as the microphone, and the directivity of the bi-directional microphone is
disposed in the horizontal direction.
[0017]
In a hands-free communication device according to the next invention, a plurality of bidirectional microphones are used as microphones, and directivity of each bi-directional
microphone is arranged in the horizontal direction and the installation angle is shifted.
[0018]
Further, in a handsfree communication device according to the next invention, a portion of the
reflector facing the speaker is spherical.
[0019]
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Furthermore, in the hands-free communication device according to the next invention, a flat
portion wider than the diaphragm area of the speaker is provided at a position opposite to the
speaker of the reflector, and a bent portion is provided around the flat portion and bent with the
flat portion. It is something that connects slowly with the department.
[0020]
DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment
Hereinafter, embodiments of the present invention will be described with reference to the
drawings.
FIG. 1 is a block diagram of the hands-free communication apparatus shown in the embodiment
1 of the present invention, and FIG. 2 is a circuit block diagram of the hands-free communication
apparatus shown in FIG. Show the function of the and omit the description.
In the figure, 1a is a housing, 2 is a speaker, 3 is a conversion circuit, 4 is a bi-directional
microphone, 8a and 8b are a plurality of speakers, 10 is a hemispherical reflector, and 47 is an
echo canceler.
[0021]
Further, FIG. 3 is a directional characteristic view seen from the top of the bi-directional
microphone 4 shown in FIG. 1. In the figure, 11 is the effective range of the bi-directional
microphone 4 and 12 is the output direction of the other party voice.
Further, although not shown, the handsfree communication device 1a shown in FIG. 1 can cope
with a plurality of speakers surrounding the handsfree communication device 1a in addition to
the speakers 8a and 8b.
[0022]
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Next, the operation will be described.
In the hands-free communication device in FIG. 1, the speaker used is only one of the speakers 2
that amplifies the other party's voice. The speaker 2 was disposed on the top surface of the
housing 1 a, and the reflector 10 was disposed on the central axis of the speaker 2. Thereby, the
other party's voice expanded from the speaker 2 is uniformly reflected in all directions by the
reflector 10. That is, the other party's voice of the same sound pressure is output to the plurality
of speakers 8a and 8b surrounding the hands-free communication device shown in FIG.
[0023]
Further, in the hands-free communication device shown in FIG. 1, two speakers output voices of
opposite phases and do not cancel each other as in the hands-free communication device shown
in FIG. The output characteristics become flat as shown by G1 in FIG. 15 at least at 1 KHz or less,
and the other party's voice is easy for the speakers 8a and 8b to hear.
[0024]
In addition, the bi-directional microphone 4 is disposed on the reflector 10 on the central axis of
the speaker 2.
As a result, as shown in FIG. 3, the sound pressure and the phase of the other-party voice 12 that
is routed from the speaker 2 to the bi-directional microphone 4 are completely equal on the left
and right of the diaphragm (not shown) in the bi-directional microphone 4 .
[0025]
As a result, the diaphragm in the bi-directional microphone 4 does not vibrate depending on the
opposite side voice 12 as the opposite side voice 12 from the left and right sides is offset. That is,
since the bi-directional microphone 4 does not pick up the other party's voice 12, echo, howling,
etc. are less likely to occur. Also, the bi-directional microphone 4 can pick up the own-side
speech emitted by the speakers 8 a and 8 b within the effective range of the bi-directional
microphone 4.
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[0026]
Further, as shown in FIG. 2, since the second speaker 14 shown in FIG. 13 is not required, the
delay circuit portion (not shown) and the delay circuit 46 included in the adaptive filter 45 as
shown in FIG. And only the echo canceller 47 is required. The echo canceller 47 generates a
pseudo echo while learning the transfer characteristic of the wraparound path from the speaker
2 to the bi-directional microphone 4. As a result, by subtracting the pseudo echo signal from the
opposite voice 12 picked up by the bi-directional microphone 4 without canceling out with the
configuration of FIG. 1, only the loop signal can be erased.
[0027]
Second Embodiment FIG. 4 is a block diagram of the hands-free communication apparatus shown
in the second embodiment of the present invention. The same reference numerals as in FIG. 1
denote the same or equivalent functions, and a description thereof will be omitted. In the figure,
reference numerals 41 and 42 denote bi-directional microphones. Further, FIG. 5 is a directional
characteristic view seen from the upper surface of the bidirectional microphones 41 and 42
shown in FIG. 4, and FIG. 5 (1) is a directional characteristic of each of the bidirectional
microphones 41 and 42; ) Shows the directivity characteristic in which the bi-directional
microphones 41 and 42 are synthesized. In the figure, 411 is the effective range of the bidirectional microphone 41, and 421 is the effective range of the bi-directional microphone 42.
[0028]
The effective range of a general bi-directional microphone is bi-directionally distributed as the
effective range 11 of the bi-directional microphone 4 shown in FIG. Further, when using the
hands-free communication device of FIG. 1 with a plurality of persons surrounding a circular
table, a sufficient effective range can not be secured by using only one bi-directional microphone
4 shown in FIG. Therefore, as shown in FIG. 5, the effective range is expanded as shown in FIG. 5
(2) by arranging each of the angles by, for example, 90 degrees using two bi-directional
microphones 41 and 424.
[0029]
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By applying this, by using a plurality of bi-directional microphones 4 and shifting the installation
angle, a wider effective range can be obtained. Also in this case, echo and howling do not occur
easily because each bi-directional microphone does not pick up the other party's voice.
[0030]
Third Embodiment In the third embodiment, the shape of a reflector suitable for the other party's
voice at the speaker position shown in FIG. 1 is examined by analysis. FIG. 6 is an explanatory
diagram of an observation method for observing the frequency characteristic of the other party's
voice at the speaker position using the reflector shown in the third embodiment of the present
invention. In the third embodiment, three speaker positions are provided as shown in FIG. 6 as
observation points of the other party's voice. The observation points are as follows.
[0031]
A point 400 mm above the lower surface of the housing 1 a and 500 mm apart horizontally from
the center of the housing 1 a is taken as an observation point 1. A point 400 mm above the lower
surface of the housing 1 a and 1000 mm horizontally away from the center of the housing 1 a is
taken as an observation point 2. A point 400 mm above the lower surface of the housing 1a and
1500 mm horizontally from the center of the housing 1a is taken as the observation point 3.
[0032]
At the time of observation, a cylindrical casing 1a having a diameter of 100 mm and a height of
100 mm was used. In addition, the diameter of the diaphragm of the speaker 2 disposed on the
top surface of the housing 1a was 6.6 cm. Hereinafter, description of FIGS. 7 to 12 showing
observation results will be made.
[0033]
7 is an explanatory view of the observation result in the case where the reflector 10 is not
provided, the configuration of the hands-free communication device to be observed in FIG. 7 (1),
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the sound pressure distribution at a frequency of 1100 Hz (FIG. 7 (2) FIG. 7 (3) shows frequency
characteristics (horizontal axis-frequency (Hz), vertical axis-sound pressure (dB)) at observation
points 1 to 3. FIG. 8 is an explanatory view of an observation result in the case where a conical
reflector 10 with a diameter of 100 mm and a height of 70 mm is provided to face the speaker 2
and the configuration of the hands-free communication device observed in FIG. Fig. 8 (2) shows
the sound pressure distribution at a frequency of 1100 Hz (in dB), Fig. 8 (3) shows the frequency
characteristics at observation points 1 to 3 (horizontal axis-frequency (Hz), vertical axis-sound
pressure (dB) )).
[0034]
9 is an explanatory view of the observation result in the case where a hemispherical reflector 10
with a diameter of 300 mm is provided to face the speaker 2 and the configuration of the handsfree communication device observed in FIG. 9 (1); Shows the sound pressure distribution (in dB)
at a frequency of 1100 Hz, and FIG. 9 (3) shows the frequency characteristics (horizontal axisfrequency (Hz), vertical axis-sound pressure (dB)) at observation points 1 to 3 . FIG. 10 is an
explanatory view of the observation result in the case where a hemispherical reflector 10 with a
diameter of 400 mm is provided to face the speaker 2 and the configuration of the hands-free
communication device observed in FIG. Shows the sound pressure distribution (in dB) at a
frequency of 1100 Hz, and FIG. 10 (3) shows the frequency characteristics (horizontal axisfrequency (Hz), vertical axis-sound pressure (dB)) at observation points 1 to 3 .
[0035]
· Fig. 11 shows the observation results when the reflector 2 facing the speaker 2 is provided with
a diameter of 300 mm on the upper surface, a diameter of 100 mm on the lower surface, and a
height of 150 mm. 11 (1) shows the configuration of the hands-free communication device to be
observed, FIG. 11 (2) shows the sound pressure distribution (unit: dB) at a frequency of 1100 Hz,
and FIG. 11 (3) shows the observation points 1 to The frequency characteristic in 3 (horizontal
axis-frequency (Hz), vertical axis-sound pressure (dB)) is shown. · In Fig. 12, facing the speaker 2,
the upper surface diameter 300mm, the lower surface diameter 100mm, the height 150mm and
the extension of the lower surface are connected by a bent portion with a radius of 100mm. It is
explanatory drawing of the observation result at the time of providing the connected bowlshaped reflector 10, and it is characterized by having connected gently the turning point of a
lower surface part and a bending part. 12 (1) shows the configuration of the hands-free
communication device to be observed, FIG. 12 (2) shows the sound pressure distribution at a
frequency of 1100 Hz (in dB), and FIG. 12 (3) shows the frequencies at observation points 1 to 3.
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The characteristic (horizontal axis-frequency (Hz), vertical axis-sound pressure (dB)) is shown.
[0036]
The wavelength L of the sound wave can be generally determined by L = 340 m / F (F is the
frequency), and the wavelength at 500 Hz is about 68 cm, and the wavelength at 1000 Hz is
about 34 cm. Moreover, in the sound pressure distribution of (2) of FIGS. 7-12, it shows that it is
a location where a sound pressure is so high that a lightness is brighter. Moreover, the frequency
characteristic of (3) of FIGS. 7-12 observed the range of 100 Hz-3.5 KHz made sufficient enough
to judge a human voice. In addition, observation point 1 is indicated by 0.5 m, observation point
2 by 1.0 m, and observation point 3 by 1.5 m.
[0037]
As seen from FIGS. 7 to 12 (3), the frequency characteristics from 100 Hz to 1 KHz are stable,
and no significant difference is seen. However, a drop in the frequency response is observed
around 1 KHz. This is considered to be because the directivity of the sound pressure distribution
can be seen as the frequency becomes higher, and a portion with low sound pressure is applied
to the observation point. For example, the sound pressure distribution at 1100 Hz when there is
no reflector is as shown in FIG. 7 (2), and it can be seen that the sound pressure near the
observation point is just low.
[0038]
Also, even when FIG. 7 (2) and FIG. 8 (2) are compared, no significant difference is found in the
sound pressure distribution. The reason is considered that the wavelength of 1100 Hz is about
31 cm, and the light is transmitted through the conical reflector 10 having a diameter of 100 mm
and a height of 70 mm. Further, in FIG. 9 (2), it can be seen that the portion where the sound
pressure distribution is high is directed to the speaker direction along the extension of the
reflector 10. In FIG. 10 (2), the tendency is further strengthened.
[0039]
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Moreover, when FIG. 9 (3) and FIG. 10 (3) are compared, the drop of the frequency characteristic
occurred at 2 KHz or less in FIG. 9 (3), but the drop to about 4 KHz is seen in FIG. 10 (3) I can
not. That is, the sound pressure distribution in the case of using the reflector 10 shown in FIG. 10
(1) seems to show no drop since the portion with high sound pressure is always applied to the
speaker position up to about 4 KHz. That is, at the speaker position, the hands-free
communication device using the reflector 10 of FIG. 10 (1) seems to be easier to hear than the
hands-free communication device using the reflector 10 of FIG. 9 (1).
[0040]
Also, looking at FIG. 11 (2), the high sound pressure distribution points toward the speaker along
the extension of the reflector 10 as in FIG. 10 (2), but it is parallel to the curve of 400 mm
diameter of the reflector 10. I see that there is a downturn. Further, the drop shown in FIG. 11 (2)
is eliminated in FIG. 12 (2). That is, the drop shown in FIG. 11 (2) is considered to occur because
the joint between the lower surface and the bending portion suddenly changes. On the other
hand, in FIG. 12 (2), since the joint between the lower surface portion and the bending portion
gradually changes, it is considered that the problem seen in FIG. 11 (2) is solved.
[0041]
Also, looking at FIG. 12 (3), no sharp drop is seen at any of the observation points. The reason is
considered to be that the shape of the reflector 10 of FIG. 12 (1) has a gentle horn shape for the
speaker 2 and the irregular reflection decreases.
[0042]
Thus, at the speaker position set in the third embodiment, (1) When the radius of the portion
facing the speaker 2 of the reflector 10 is spherical at least 30 cm or more, the directivity of
about 1100 Hz is on the extension of the reflector It will turn to the direction of the speaker
along. (2) When the portion of the reflector 10 facing the speaker 2 is spherical and has a radius
of at least 40 cm, the drop in sound pressure is eliminated up to about 4 KHz at the speaker
position. (3) A flat portion wider than the diaphragm area of the speaker is provided at a position
opposite to the speaker 2 of the reflector 10, and a bent portion is provided around the flat
portion and the transition between the flat portion and the bent portion is loosely connected The
frequency characteristics at the speaker position and the speaker position show ideal
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characteristics.
[0043]
According to the present invention, in the hands-free communication device, the speaker for
outputting the other party's voice vertically upward is provided on the top surface of the housing,
and the other party's voice output from the speaker is reflected. A reflector for converting the
output direction is provided opposite to the speaker, and a microphone for inputting voice from
the speaker is provided on the upper surface of the reflector. There is an effect that the side voice
can be output.
[0044]
Further, according to the next invention, the hands-free communication device uses the bidirectional microphone as the microphone and arranges the directivity of the bi-directional
microphone in the horizontal direction, so that the other party's voice output by the speaker
wraps around The bi-directional microphone has an effect that the other party's voice is not
input.
[0045]
Further, according to the next invention, the hands-free communication device uses a plurality of
bi-directional microphones as the microphones and arranges the directivity of each bi-directional
microphone in the horizontal direction and shifts the installation angle. There is an effect that the
synthesized directivity of a plurality of bi-directional microphones is further expanded and the
speaker voice can be more easily picked up.
[0046]
Further, according to the next invention, the hands-free communication device has a spherical
shape on the portion facing the speaker of the reflector, so that it has an effect of being able to
reflect the other party's voice more and direct it in the direction of the speaker position.
[0047]
Furthermore, according to the next invention, in the hands-free communication device, a flat
portion wider than the diaphragm area of the speaker is provided at a position facing the speaker
of the reflector, and a bending portion is provided around the flat portion. Since the transition
between the and the bent portion is connected gently, the frequency characteristic of the other
party's voice at the speaker position becomes flat, and the drop of the frequency characteristic is
reduced.
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