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JP2010147692

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DESCRIPTION JP2010147692
The present invention provides a sound collection device with a small error with respect to a
desired directivity. A unidirectional microphone (12A), a unidirectional microphone (12B), and a
unidirectional microphone (12C) are arranged on one plane (a plane parallel to the upper surface
of a housing). The maximum sensitivity direction is oriented inward in the array. The back of
each unidirectional microphone (in the direction in which the sensitivity is minimized) is
acoustically open. The direction of maximum sensitivity of each unidirectional microphone is
directed inward in the array, so that the position of the vibration plane of each unidirectional
microphone can be approximated to the center position of the array. Thus, by adjusting the gain
of the sound collected by each unidirectional microphone, directivity can be freely formed on the
plane with a smaller error. [Selected figure] Figure 6
Sound pickup device
[0001]
BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a
sound pickup device for picking up sound around a housing.
[0002]
Conventionally, as a device for picking up the sound around the housing, there is, for example, a
device as described in Patent Document 1.
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The device of Patent Document 1 is referred to as a microphone (hereinafter simply referred to
as a microphone) on each surface of the tetrahedron. ) And can pick up sound in all directions.
[0003]
In addition, the sound collection directions of the three unidirectional microphones are arranged
to be shifted outward by 120 degrees, sound in all circumferential directions is collected, and the
sound collection levels of the respective unidirectional microphones are An apparatus for
detecting a direction has also been proposed (e.g., Patent Document 2).
[0004]
Furthermore, an apparatus for collecting sound in any direction using a plurality of microphones
has also been proposed (for example, Patent Document 3).
JP-A-51-32319 JP-A-2001-153941 JP-A-2008-48355
[0005]
In Patent Document 2, although any sound can be picked up in three directions at 120 degrees
each, there is no angular resolution higher than that, and directivity can not be freely formed in a
desired direction. The
[0006]
Further, the devices of Patent Documents 1 to 3 have a problem that the error with respect to the
desired directivity becomes large particularly in a high frequency band such as 1 kHz or more
because the vibration planes of the respective microphones are separated.
[0007]
Therefore, an object of the present invention is to provide a sound collection device having a
small error with respect to desired directivity.
[0008]
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The sound collection device of the present invention is a sound collection device having a
plurality of unidirectional microphones.
The plurality of unidirectional microphones are arranged on one plane.
Also, the direction of the sensitivity maximum of each unidirectional microphone is arranged in
the inward direction of the array.
Furthermore, the sound collection device includes a plurality of gain adjustment units that adjust
the gain of the sound collected by each microphone, and an addition unit that adds the sound
after gain adjustment.
[0009]
Thus, in the sound collection device of the present invention, by directing the direction of the
sensitivity maximum of each microphone in the inward direction of the array, the vibration plane
can be arranged closer than in the case of being directed outward. Therefore, when the signals
are added by the adding unit, the time lag between the signals obtained on the vibration planes
of different microphones becomes smaller, and the error with respect to the desired directivity
can be reduced.
[0010]
Therefore, according to the sound collection device of the present invention, it is possible to
reduce the error with respect to the desired directivity even in a high frequency band such as 1
kHz or more.
[0011]
Further, a vertical unidirectional microphone having a sensitivity maximum direction opposite to
the direction toward the plane is further arranged at a position different from one plane formed
by the plurality of unidirectional microphones. It is also good.
[0012]
In this case, in addition to the above plane, directivity can be formed also in the direction in
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which the vertical unidirectional microphone is disposed, and directivity in a desired direction
can be made free in the three-dimensional direction (global direction). Can be formed.
[0013]
In addition, the plurality of unidirectional microphones have a circumference centered on the one
point such that the directional axes (the axes in the direction of maximum sensitivity) of the
unidirectional microphones cross at one point. It is good also as an aspect arranged above.
[0014]
According to the present invention, the sound collecting surfaces of the plurality of directional
microphones can be arranged in proximity to each other, and the error with respect to the
desired directivity can be reduced.
[0015]
1 to 4 are external views showing the configuration of the sound collection device of the present
embodiment.
1 is a front view, FIG. 2 is a rear view, FIG. 3 is a left side view, and FIG. 4 is a plan view.
In FIGS. 1 to 4, the right side of the sound collection device is X, the left side is -X, the upper side
is Y, the lower side is -Y, the front side is Z, and the back side is -Z.
[0016]
A casing 11 which is a base of the sound collection device 1 is in the form of a thin rectangular
solid in the vertical direction, and is made of, for example, a resin material.
Three columns 13A, columns 13B, and columns 13C are vertically mounted on the top surface of
the housing 11 on the top surface of the housing 11.
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Each support is also made of, for example, a resin material.
[0017]
The column 13A is attached to the front side of the apparatus, the column 13B is attached to the
right rear side of the apparatus, and the column 13C is attached to the left rear side of the
apparatus.
As shown in the plan view of FIG. 4, the columns are equally spaced at an interval of 120 degrees
equidistant from the central position of the housing.
[0018]
Plate-like elastic rubber 131A, elastic rubber 131B, and elastic rubber 131C which are thin in the
vertical direction are attached to the top surfaces of the columns 13A, 13B, and 13C,
respectively. The elastic rubber 131A, the elastic rubber 131B, and the elastic rubber 131C
respectively extend toward the center of the housing, and the microphone frame 14A, the
microphone frame 14B, and the joint portion 141A provided at the lower portion of the
microphone frame 14C. , Joint portion 141B, and joint portion 141C.
[0019]
The microphone frame 14A, the microphone frame 14B, and the microphone frame 14C have a
cylindrical shape, and it is possible to fit a cylindrical microphone (unidirectional microphone)
into the hollow inside thereof. The open portions of the cylindrical bottom surface of each
microphone frame face in directions shifted by 120 degrees in a state where the sound collection
device is viewed in plan.
[0020]
That is, the open portion of the cylindrical bottom surface of the microphone frame 14A is
directed to the front and back of the device, and the directivity of the unidirectional microphone
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can be installed to be directed to the front or back of the device. There is. As shown in FIG. 4, in
the present embodiment, the direction (maximum sensitivity direction) of the sensitivity
maximum of the unidirectional microphone 12A inserted into the microphone frame 14A is
directed to the rear side of the apparatus. The maximum sensitivity direction of this
unidirectional microphone 12A is 0 degrees.
[0021]
Further, the open portion of the cylindrical bottom surface of the microphone frame 14B is
directed to the right rear and left front directions of the apparatus. In the present embodiment,
the maximum sensitivity direction of the unidirectional microphone 12B fitted in the microphone
frame 14B is directed to the left front side of the apparatus. That is, the housing is directed to an
angle (direction of +120 degrees) of left rotation 120 degrees from the above-mentioned 0
degree in plan view.
[0022]
Further, the open portion of the cylindrical bottom surface of the microphone frame 14C is
directed to the left rear side and the right front side of the apparatus. In the present embodiment,
the maximum sensitivity direction of the unidirectional microphone 12C to be fitted into the
microphone frame 14C is directed to the right front side of the apparatus. That is, the housing is
oriented in a plane (in the direction of -120 degrees or +240 degrees) from the above-mentioned
0 degree to right rotation 120 degrees in plan view.
[0023]
Furthermore, in a state where the sound collection device 1 is viewed in plan, a cylindrical
microphone frame 14L is provided on the case center side of each microphone frame (maximum
sensitivity direction of each directional microphone). As shown in FIGS. 1 to 3, the microphone
frame 14L is provided on the upper surface side of the microphone frame 14A to the
microphone frame 14C, and the open portion of the cylindrical bottom surface faces the device
upper surface side and the lower surface side. There is. In the present embodiment, the maximum
sensitivity direction of the unidirectional microphone 12L to be fitted into the microphone frame
14L is directed to the upper surface side of the apparatus.
04-05-2019
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[0024]
The microphone frame 14A, the microphone frame 14B, the microphone frame 14C, and the
microphone frame 14L are formed by integral molding of resin molds, and four microphones
fitted in the respective frames can be fixed as one unit. It is supposed to be.
[0025]
The frame integrally formed has the directivity axes (axis of the maximum sensitivity direction) of
the unidirectional microphone 12A, the unidirectional microphone 12B, and the unidirectional
microphone 12C in a state where the sound collection device is viewed in plan. It is formed to
cross at one point.
In the sound collection device of the present embodiment, the central axis of the case of the
sound collection device 1 crosses the directivity axis by adjusting the shapes of the three
columns, the elastic rubber, and the joint portion and the installation position. And the same.
[0026]
With this structure, the unidirectional microphone 12A, the unidirectional microphone 12B, and
the unidirectional microphone 12C are arranged on one plane (a plane parallel to the upper
surface of the housing), and each of the unidirectional microphones is The maximum sensitivity
direction is oriented inward in the array. That is, the uni-directional microphones are arranged
inward on the circumference centered on the point at which the directional axes cross. In this
way, by directing the maximum sensitivity direction of each microphone in the inward direction
of the array, the vibration planes can be disposed closer to each other than directed outward. As
a result, the position of the vibration plane of each unidirectional microphone can be
approximated by the point at which the directivity axes cross. Therefore, directivity control on
the plane can be realized with a small error even in a high frequency band such as 1 kHz or
more.
[0027]
Also, the four microphones are fixed in a state of floating in the air away from the top surface of
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the housing 11 by the support, the elastic rubber, and the joint portion. In particular, the vertical
unidirectional microphone 14L is disposed on the upper surface side of the plane formed by the
unidirectional microphone 12A, the unidirectional microphone 12B, and the unidirectional
microphone 12C. It is arranged at the position farthest from the top surface of 11. For this
reason, the back of the unidirectional microphone 14L is also acoustically released.
[0028]
Next, directivity control of the sound collection device 1 will be described. FIG. 5A is a block
diagram showing the configuration of the audio signal processing system of the sound collection
device. FIG. 6 is a schematic diagram showing an aspect of directivity control. The characteristics
shown in FIG. 6 show ideal characteristics for the purpose of explanation, and are not diagrams
showing actual characteristics.
[0029]
The sound collection device 1 includes a signal processing unit 3 including a gain adjustment
unit 31A, a gain adjustment unit 31B, a gain adjustment unit 31C, a gain adjustment unit 31L,
and an addition unit 32 as a configuration of a signal processing system.
[0030]
The audio signals output from the unidirectional microphones are gain-adjusted by the gain
adjustment units of the signal processing unit 3, and then added by the addition unit 32.
The sound collection device 1 can form arbitrary directivity around the device by controlling the
gain of each gain adjustment unit.
[0031]
The gain (G1, G2, G3) of the gain adjustment unit 31A, the gain adjustment unit 31B, and the
gain adjustment unit 31C is assumed to be θ in the direction of forming directivity (the angle in
the maximum sensitivity direction) and f as the weighting coefficient of the microphone. , Is
determined as follows. G1 = 2/3 × {1-f (1-2 cos θ)} G2 = 2/3 × {1-f (1-2 cos (θ-120 °))} G3 =
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2/3 × {1-f (1 −2 cos (θ + 120 °)) Note that the weighting factor f is a factor that determines
the form of directivity, and is a value of 0 or more and 1 or less. For example, it becomes
omnidirectional at f = 0, unidirectional at f = 0.5, and bidirectional at f = 1. Here, directivity can
be formed in any direction by arbitrarily determining the value of θ. For example, as shown in
FIG. 6A, when forming a single directivity on the front side (Z direction) of the apparatus, that is,
θ = 180 degrees, the value of each gain is set to a weighting factor f = 0.5, It becomes (G1, G2,
G3) = (-1/3, 2/3, 2/3). The signal M to be output is M = G1 × M1 + G2 × M2 + G3 × M3 =,
using M1, M2, and M3 which are output signals of the unidirectional microphone 12A, the
unidirectional microphone 12B, and the unidirectional microphone 12C. It is represented by
−1⁄3 × M1 + 2/3 × M2 + 2/3 × M3. As a result, as shown in FIG. 6B, the angle in the direction
of maximum sensitivity of the synthetic characteristics of the three microphones can be 180
degrees, and the direction of minimum sensitivity can be oriented in the direction of 0 degrees.
That is, unidirectionality can be formed in the direction of θ = 180 degrees.
[0032]
In the sound collection device of the present embodiment, as described above, the directional axis
crosses the position of the vibration plane of each unidirectional microphone by pointing the
maximum sensitivity direction of each microphone in the inward direction of the array (center
The gain can be approximated and the error for the desired directivity can be sufficiently
reduced even in a high frequency band such as 1 kHz or more according to the above-mentioned
equation for gain.
[0033]
FIG. 7 is a diagram showing directivity characteristics (gain for each angle) obtained when the
distance of the microphone pickup surface from the center position is changed.
In the figure, the directivity characteristics of 1 kHz, 2 kHz, 4 kHz and 8 kHz obtained when the
distance from the center position to the microphone vibration plane is 3 mm, 6 mm and 10 mm
are shown.
[0034]
As shown in the figure, the smaller the distance from the center position to the microphone
vibration surface, the smaller the minimum value of sensitivity near 0 degrees, even at high
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frequencies. That is, the characteristics as single directivity can be obtained up to high
frequencies.
[0035]
For example, assuming that the thickness of each unidirectional microphone is about 3 mm, from
the center position to the microphone vibration surface in the case where the maximum
sensitivity direction of each microphone is directed outward and inward of the array. The
distance of is different by about 3 mm. That is, the difference between the characteristic of 3 mm
and the characteristic degree of 6 mm shown in FIG. 7 occurs (a difference of about 6 dB occurs
at the minimum value of sensitivity).
[0036]
Therefore, it can be said that directing the maximum sensitivity direction of each microphone in
the inward direction of the array is effective for realizing directivity formation even in a high
frequency band such as 1 kHz or more (the vibration plane of each microphone It can be said
that the position can be approximated by the center position).
[0037]
In the sound collection device of the present embodiment, the unidirectional microphone 12A,
the unidirectional microphone 12B, and the unidirectional microphone 12C are arrayed by using
the unidirectional microphone 14L in the vertical direction. It is possible to form directivity in
any direction not only on the flat plane but also on the top side of the device.
For example, as shown in FIG. 8, it is based on a horizontal microphone (unidirectional
microphone 12A, unidirectional microphone 12B, and unidirectional microphone 12C
synthesized) forming unidirectionality in the direction of θ = 180 degrees. If the gain for the
audio signal and the gain for the audio signal of the unidirectional microphone 14L in the
vertical direction are adjusted to be the same, the directivity axis can be formed on the front side
of the device (in the Y and Z directions).
[0038]
Note that since the unidirectional microphone 12A, the unidirectional microphone 12B, and the
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unidirectional microphone 12C actually have sensitivity also on the lower surface side of the
housing, the sound collection device of this embodiment is used. In the above, directivity can be
freely formed in a three-dimensional direction (global direction).
[0039]
In addition, said arrangement | positioning aspect of each uni-directional microphone is not
restricted to said example.
For example, the arrangement mode as shown in FIG. 5 (B) may be used.
[0040]
FIG. 5B shows an example of an arrangement in which the unidirectional microphone 12B and
the unidirectional microphone 12C are opposed to each other. In this case, the maximum
sensitivity direction of the unidirectional microphone 12B is the left side of the apparatus
(direction of θ = 90 degrees), and the maximum sensitivity direction of the unidirectional
microphone 12C is the left side (θ = −90 degrees) Direction). Thus, even in the case where the
unidirectional microphone 12B and the unidirectional microphone 12C face each other,
directivity can be formed in any direction. In the example illustrated in FIG. 5B, the gains (G1, G2,
and G3) of the gain adjustment unit 31A, the gain adjustment unit 31B, and the gain adjustment
unit 31C are set as follows.
[0041]
In this case, when θ = 180 degrees, that is, when forming a single directivity on the front side of
the device, assuming that the directivity coefficient f = 0.5, the value of each gain is (G1, G2, G3)
= (− 1, It becomes 1, 1). In this way, as long as three or more unidirectional microphones are
arranged on one plane and the direction of maximum sensitivity of each unidirectional
microphone is directed inward in the array, any arrangement manner However, it is possible to
realize the sound collection device of the present invention.
[0042]
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In the above example, although the example in which three microphones are arranged in the
same plane has been described, it is needless to say that a larger number of microphones may be
arranged in the same plane. In addition, the single directional microphone in the vertical
direction is not limited to one, and a plurality of microphones may be further provided. For
example, it may further include a microphone having directivity in the opposite direction to the
vertical unidirectional microphone 14L.
[0043]
It is a front view of a sound collection apparatus. It is a rear view of a sound collection apparatus.
It is a left view of a sound collection device. It is a top view of a sound collection device. It is a
block diagram which shows the structure of the audio | voice signal processing system | strain of
a sound collection apparatus. It is a schematic diagram showing an aspect of directivity control. It
is a figure showing the directional characteristic obtained when changing the distance of the
microphone sound collecting surface from the center position. It is a schematic diagram showing
an aspect of directivity control in the upper surface direction.
Explanation of sign
[0044]
1- Sound pickup device
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