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JPH04109798

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DESCRIPTION JPH04109798
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
sound field reproduction system from sound collection to reproduction when playing music or
shooting with a camera integrated VTR. 2. Description of the Related Art In recent years, the
performance of consumer audio recording devices has been rapidly improved as seen in digital
audio tape recorders. Also, even with a camera integrated video photographing apparatus,
performing so-called high fidelity 2-channel recording is becoming mainstream. Hereinafter, a
conventional sound pickup apparatus will be described with reference to the drawings. FIG. 7 is a
diagram showing the configuration of a conventional sound collecting apparatus of the pair
microphone system. In FIG. 7, 101. 102 is a unidirectional microphone and 103 is a microphone
holder. The unidirectional microphones 101 and 102 are fixed to the microphone holder 103 so
that the directivity axes of the both intersect at an angle α ′ and the distance between the tip
ends of the microphones is equal to d [m]. Is usually 90 to 150 '? The interval d of the
microphone is often about 0.2 [m]. The operation of the sound collecting apparatus of the pair
microphone system configured as described above will be described. FIG. 8 is a diagram showing
the th direction of a unidirectional microphone arranged as shown in FIG. The directivity of the
unidirectional microphone, (θ) is expressed by the equation (1), where θ is an angle that makes
the directional axis direction 0 counterclockwise. D、。 (Θ) = (1 + cos (θ)) / 2− (1) When
actually collecting sound, the unidirectional microphone 101. The pair microphones are fixed
such that the direction which bisects the angle formed by the directional axes of 102 is the sound
source direction. So-called stereo reproduction can be performed by reproducing the output of
the sound pickup device of the pair microphone system by the reproduction device disposed at
the front left and right of the listening position. SUMMARY OF THE INVENTION However, in the
above-described conventional configuration, since the sensitivity in the front direction is low, a
phenomenon (center drop) in which the sound at the central portion is lost and it becomes a
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sound image separated to the left and right easily occurs. . In addition, since only the front
portion is picked up, there is a problem that the realism of the entire sound field can not be
reproduced faithfully. The present invention solves the above-mentioned problems, and has a
first object to provide a sound field reproduction system for preventing hollow spots and
faithfully reproducing the realism of the entire original sound field. Another object of the present
invention is to provide a sound field reproduction system for faithfully reproducing an original
sound field on a plane formed by orthogonal axes of bidirectional microphones.
It is a third object of the present invention to provide a sound field reproduction system for
three-dimensional reproduction of an original sound field. Means for Solving the Problems In
order to achieve the above first object, the sound field reproduction system of the present
invention comprises a nondirectional microphone, n bidirectional microphones, and a signal
reproduction system. It has a configuration provided with m speakers and signal conversion
means for inputting output signals of the (n + 1) microphones and performing conversion for
reproduction by the m speakers. Further, in order to achieve the second object, the sound field
reproduction system of the present invention has a configuration in which n = 2 and the
directional axes of two bidirectional microphones are orthogonal to each other. Furthermore, in
order to achieve the third object, the sound field reproduction system of the present invention
has a configuration in which n = 3 and the directional axes of the three bidirectional
microphones are orthogonal to each other. Operation According to the above configuration,
according to the present invention, the omnidirectional microphone picks up the realism of the
entire sound field, and by combining and having a plurality of bidirectional microphones, a
hollow is prevented. Further, by providing two bi-directional microphones in which the
directional axes are orthogonal to each other, the original sound field on the plane formed by the
orthogonal directional axes is faithfully reproduced. Furthermore, three directional microphones
having orthogonal directional axes mutually enable three-dimensional faithful reproduction of
the original sound field. Embodiments Hereinafter, one embodiment of the present invention will
be described with reference to the drawings. For example, consider a case where an original
sound field on a horizontal plane is faithfully reproduced using one nondirectional microphone,
two bidirectional microphones and four speakers. FIG. 1 is a block diagram of a sound field
reproduction system according to an embodiment of the present invention. In FIG. 1, ite, 1 and 3
are bi-directional microphones, and 2 are non-directional microphones. The bidirectional
microphones 1 and 3 are arranged such that the directivity axes are orthogonal to each other. 4.
Signal conversion means for inputting bi-directional microphone 1, 3 output and non-directional
microphone 2 output, 5 ° 6, 7. A speaker 8 reproduces the Lf-fold signal Lb-fold signal Rf-fold
signal Rb output from the signal conversion means 4. The operation of the sound field
reproduction system of the present embodiment configured as described above will be described
below. The outputs of the bidirectional microphones 1 and 3 and the nondirectional microphone
2 are converted by the signal conversion means 4 into an Lf-fold signal Lb-fold signal Rf-fold
signal Rb signal. By reproducing the 4-channel signal using the four speakers, it is possible to
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faithfully reproduce the realism of the entire sound field and to reproduce the sound field
without any omission.
2 (A) and 2 (B) are plan views showing the arrangement of the microphones of the sound field
reproducing apparatus of this embodiment. In FIG. 2, 1 and 3 are bi-directional microphones, and
2 is a non-directional microphone. The bidirectional microphones 1 and 3 are arranged such that
the directivity axes are orthogonal to each other. 21はマイクロホンホルダである。 For the
following description, the directional axis of the bi-directional microphone 1 is y-axis, and the
directional axis of the bi-directional microphone 3 is y-axis. The output of the bi-directional
microphone 1 is ○, and the output of the bi-directional microphone 2 is By. The pointing axis of
the bi-directional microphone 1.3 is shown by a broken line in FIG. The directivity of each of the
microphones is expressed by equations (2) to (4), where θ is an angle that makes the X-axis
direction O 反 counterclockwise positive. Directionality D of the bi-directional microphone 1 [lx
(θ) DIIX (θ) = = COS (θ ') (2) Directionality of the non-directional microphone 2 (Θ) Do (θ) = 1
(3) Directivity of the bi-directional microphone 3, Y (θ) D8. (Θ) = sin (θ) (4) FIG. 3 is a diagram
showing the directivity of the two bi-directional microphones and one non-directional
microphone of FIG. 3 (a) shows the directivity of the bi-directional microphone 1, FIG. 3 (b)
shows the directivity of the non-directional microphone 2, and FIG. 3 (C) shows the directivity of
the bi-directional microphone 3. It shows. The curve indicating directivity in the region of x <0 in
FIG. 3 (a) and the region of y <O in FIG. 3 (C) is a broken line, indicating that this region is in
antiphase. The It is assumed that a sound source in the positive direction of the y-axis is picked
up by the microphone having the above characteristics. The output signal BXI 01 By of each
microphone is input to the signal conversion means 4. Hereinafter, the signal conversion means
4 will be described. FIG. 4 is a block diagram showing the configuration of the signal conversion
means 4. In FIG. 4, 41 is a Bx input terminal for inputting the output of the bidirectional
microphone 1, 42 is an O input terminal for inputting the output of the nondirectional
microphone 2, and 43 is an input for inputting the output of the bidirectional microphone 1. An
input terminal 44 amplifies Bx, an amplifier circuit that generates aBx 45, an amplifier circuit
that amplifies 0, an amplifier circuit that generates aO 46, an amplifier circuit that amplifies By
and that aBy, 47 is an output aB × of the amplifier circuit 44 , A phase inverting circuit 48 for
generating an antiphase signal -aBy of the output aBy of the amplifier circuit 46, an adder 49 for
adding aBx, O, aBy, 50 for aB x ○,-Adder for adding -aBy, 51 is -a B X, O + Adder for adding aBy,
52 is -aBx, O.
An adder that adds aBy, 53 is an Lf signal output terminal that outputs the output of the adder
49, 54 is an Lb signal output terminal that outputs the output of the adder 50, 55 is an Rf signal
output that outputs the output of the adder 51 A terminal 56 is an Rb signal output terminal for
outputting the output of the adder 52. The operation of the signal conversion means 4
configured as described above will be described. The relationship between each input signal and
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the output signal of the signal conversion means 4 is expressed by the following equations (5) 弐.
Lf = a (0 + Bx + By) = 15) Lb = a (0 + Bx-By)-(6) Rf = a (0-Bx + B'Y) = 17) Rb = a (0-Bx-By) = 18) (5)
The directivity of the output signal of the signal conversion means 4 made as shown in Eq. (8) is
as shown in Eq. (9). Lf times signal directivity DLl (θ) = (1 + cos (θ) + 5 in (θ) 1/2 · (9)
Directionality of Rb signal DLb (0) = (1 + cos (θ)-sin (θ)) / 2 · (10) Rf-fold signal directivity D Rt
(θ) = f 1 −cos (θ) +5 ln (0) 1 / 2− (11) Directionality of Rb signal DRb (θ) = 11-cos (θ) -sin
The directivity shown in the expressions (θ) 1/2 · (12) (9) 弐 to (12) is shown in Figs. 5 (a) to (d).
As shown in FIG. 5, the Lf-fold signal directivity (0) is in the 135 ° direction, the directivity DLb
(θ) of the Rb signal is in the 225 ° direction, and the Rf-fold signal directivity DR2 (θ) is In the
45 ° direction, the directivity DIlb (θ) of the Rb signal has the maximum sensitivity in the 315
direction. The above is the description of the signal conversion means 4. FIG. 6 is a view showing
an example of a speaker arrangement when the output signal of the signal conversion means 4 is
reproduced. In FIG. 6, 61 is a swing room, 62 is disposed to the left of the listening position in
the listening room, and a speaker for Lf signal reproduction, 63 is disposed to the right of the
listening position in the listening room, Rf signal reproduction A speaker 64 is disposed on the
left rear of the listening position in the listening room, a speaker for reproducing the Rb signal,
and a speaker 64 disposed on the right rear of the listening position in the listening room for
reproducing the Rb signal. In the speaker arrangement of FIG. 6, by converting the signal
(reproducing the output signal of the stage 4, sound field reproduction without hollowing out is
possible. As described above, according to the present embodiment, since the microphone
sensitivity in the central portion is good, localization of the sound image is good, and by making
the directivity axes orthogonal to each other on the horizontal surface, the sound field on the
horizontal surface is uniformly collected. It is possible to faithfully reproduce the original sound
on the horizontal plane.
In addition, since there are innumerable planes formed by the directional axes of the two
bidirectional microphones in the horizontal plane, it is possible to faithfully reproduce an infinite
number of sound fields on the plane. Furthermore, when using three bi-directional microphones
whose directional axes are orthogonal to each other, for example, the case where two bidirectional microphones whose directional axes are orthogonal on a horizontal plane and a
microphone having a directional axis in the vertical direction are considered. In consideration of
this, information in the vertical direction is added to the sound field information in the horizontal
direction, and the sound field can be reproduced three-dimensionally. In this case, sound field
reproduction is performed using four or more speakers that are not on the same plane. In
addition, this sound field reproduction system is effective when applied to an air competition
monitor for funneling sound such as a hole. The sound pickup microphone of the present
invention is attached to the ceiling of the hall and reproduced with a plurality of speakers in an
air monitor studio. If the realism of the sound field can be closely monitored, more appropriate
sound adjustment can be performed. Effects of the Invention As described above, according to
the present invention, the original sound field can be faithfully reproduced by collecting sound
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with one nondirectional microphone h and n bidirectional microphones. Improve localization.
Also, by collecting sound with one nondirectional microphone and two bidirectional
microphones, it is possible to faithfully reproduce the original sound field on the plane created by
the directional axis. Further, by collecting sound with one nondirectional microphone and three
bidirectional microphones, an effect of three-dimensionally reproducing the original sound field
can be obtained.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a block diagram of a sound field reproduction system according to an embodiment of
the present invention, FIG. 2 is a plan view showing the arrangement of microphones according
to the embodiment, and FIG. 3 (a) is directivity of the bidirectional microphone 1 3 (b) shows the
directivity of the nondirectional microphone 2, FIG. 3 (C) shows the directivity of the bidirectional
microphone 3, FIG. 4 shows the signal FIG. 5 (a) is a characteristic diagram showing Lf-fold signal
directivity DLL (θ), and FIG. 5 (b) is Lb-fold signal directivity 1. FIG. 5 (C) is a characteristic
diagram showing Rf-fold signal directivity DR, (θ). FIG. 5 (d) is a characteristic diagram showing
directivity Dbb (0) of Rb signal. 6 is a plan view showing an example of the speaker arrangement
before the output signal reproduction of the signal conversion means, FIG. 7 is a plan view
showing the arrangement configuration of the conventional sound pickup device of the pair
microphone system, and FIG. It is a characteristic view which shows the directivity of the
unidirectional microphone arrange | positioned like a figure.
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