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JP2011029765

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DESCRIPTION JP2011029765
PROBLEM TO BE SOLVED: To provide a boundary microphone having a shape for enhancing a
shielding effect against an electromagnetic wave. SOLUTION: A base 1 made of metal, a cover 1
made of metal and having a plurality of holes for introducing sound waves, a microphone unit 3
disposed on the base 2 for converting sound into an electric signal, and the cover 1 on the base 2
The cover 1 has a flange portion around the periphery, and the flange member of the cover 1 is
pressed against the base 2 by pressing the flange portion of the cover 1 to the base 2 It is in
surface contact. [Selected figure] Figure 1
バウンダリーマイクロホン
[0001]
The present invention relates to a boundary microphone mainly used on a desktop, and more
particularly, to a boundary microphone having a shape for enhancing the shielding effect against
electromagnetic waves.
[0002]
There are boundary microphones that are mainly used on the desktop.
FIG. 11 shows an example of a conventional boundary microphone. In FIG. 11, reference numeral
17 denotes the base of the boundary microphone. The base 17 is made of flat metal and can be
fixed to a desk or a floor surface. A recess (depression) for mounting the circuit board 18 and the
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like is formed on the upper surface of the base 17. From an upper surface of the base 17, a pillar
11 for connecting a cover 20 described later stands up by integral molding at a substantially
central portion when the base 17 is viewed in a plane direction. Screw holes 12 are formed in the
column 11 from the upper end side. The base 17 has a front side on the left side and a rear side
on the right side in FIG. 11, a wall is integrally formed at the rear end of the base 17, and the
bush 14 is fitted in a hole formed through the wall. ing. In the case of a boundary microphone
installed in a conference hall, the front side is directed to the attendee and installed on a desk or
the like. One end of the microphone cord 15 is passed through the central hole of the bush 14.
The microphone code 15 is generally a two-core balanced output code, and a code having a
configuration in which a shield wire wraps these codes is used. The end portions of the two-core
signal wire and the shield wire constituting the microphone cord 15 are connected to
predetermined soldered lands or the like of the circuit board 18 described below.
[0003]
The circuit board 18 is fixed to the upper surface of the base 17 in a substantially front half
portion of the recess so as to close the recess. A microphone unit 16 is attached to the upper
surface of the circuit board 18 with the introduction port of the sound wave directed forward.
The microphone unit 16 generally uses a condenser type microphone unit. The base 17 is
covered with a cover 20 that covers the entire top surface of the base 17 including the
microphone unit 16 and the circuit board 18. The cover 20 is made of a metal part in the same
manner as the base 17, and an infinite number of openings are formed to guide the sound wave
to the microphone unit 16. The cover 20 is often made of, for example, a punching metal formed
by punching out an infinite number of holes. The cover 20 is press-formed into a flat plate shape,
and is placed on the upper surface of the base 17 in the form of a face down. When the cover 20
is viewed from the plane direction, a recess is formed at a position substantially corresponding to
the column 11 of the base 20 at the center, and a hole is formed at the bottom of the recess. A
screw 13 as a fastening member is inserted into the hole, and the screw 13 is screwed into the
screw hole 12 formed in the pillar 11, whereby the cover 20 is fastened to the base 17. The head
of the screw 13 is recessed in the recess of the cover 20. A receiving portion for the peripheral
edge of the cover 20 is formed on the upper surface of the base 17, and the peripheral edge of
the cover 20 contacts the base 17 with the cover 20 fastened to the base 17 with the screw 13
as described above. It is designed to
[0004]
As described above, the boundary microphone is mainly composed of the two parts of the base
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17 and the cover 20 in appearance, and the built-in parts are incorporated in the internal space
thereof. The base 12 and the cover 20 are fastened to each other by screwing the screw 13
inserted into the hole of the cover 20 into the screw hole 12 of the base 17. The base 17 and the
cover 20 are fastened with one screw 13 substantially at the center of the cover 12, and the head
of the screw 13 is configured to fit in the recess of the cover 20.
[0005]
In the internal space surrounded by the base 17 and the cover 20, in addition to the microphone
unit 16 and the circuit board 7, electrical circuits such as an impedance converter, a sound
quality adjustment circuit, and an output circuit are incorporated. When an electromagnetic wave
enters the electric circuit from the outside, the electromagnetic wave is detected by a
semiconductor element used in an impedance converter or the like, mixed in a voice signal as a
noise signal, and the signal-to-noise ratio of the microphone output (S / N Degrade). Therefore, it
is desirable that the joint portion at the peripheral portion of the base 17 and the cover 20 be
joined without a gap to shield the built-in parts, that is, to have a structure to prevent the
penetration of electromagnetic waves from the outside. This is because high frequency noise may
enter from the gap if the junction does not join well and the base 17 and the cover 20 make
point contact and there is a gap between them.
[0006]
However, the conventional boundary microphone as described above has a structure in which the
base 17 and the cover 20 are easily in point contact, for the reasons described below. The base
17 is generally manufactured by a zinc die casting method or the like, but the casting surface is
not flat. On the other hand, the cover 20 is generally made of punched metal as a material and is
press-formed into a target shape, but the peripheral portion electrically and mechanically in
contact with the base 17 is not flat and has unevenness. It is happening. Therefore, even if the
cover 20 is put on the base 17 and fastened with the screw 13, the base 17 and the cover 20 are
in point contact.
[0007]
As an example of a boundary microphone provided with a structure for blocking high frequency
from invading the microphone unit, the one described in Patent Document 1 is known. According
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to the invention described in Patent Document 1, the embedded component is disposed in the
space surrounded by the base and the cover, and the embedded component further includes a
base, a cover, a first metal component, and a peripheral portion overlapping alternately. Since it
is surrounded by the second metal part, it is possible to more effectively block the
electromagnetic wave that is going to approach from the outside toward the built-in part. For
example, even if the mobile phone is used in the vicinity of the microphone, the electromagnetic
wave can be prevented from intruding into the built-in component, and the generation of noise
due to the electromagnetic wave can be prevented. By overlapping the peripheral portions of the
first metal part and the second metal part on the inside and the outside and arranging the built-in
parts in the space surrounded by the first metal part and the second metal part, the shielding
effect is further enhanced. It can be further enhanced.
[0008]
However, since the boundary microphone in the invention described in Patent Document 1 uses
the first metal mesh and the second metal mesh in an overlapping manner, there is a gap at the
junction of the first and second metal meshes. There are also things that can be done, and the
shielding effect has room for improvement. In addition, even if the metal mesh is electrically
connected partially with the boundary plate with a screw or the like, the connection becomes
discontinuous and there is room for improvement in order to reliably prevent the penetration of
electromagnetic waves. . In addition, since it is necessary to use a metal mesh, there is a problem
that the cost is increased accordingly.
[0009]
On the other hand, conventional boundary microphones have a circular shape as shown in FIG.
12 and FIG. 12 and 13, the circular boundary microphone is covered with a base 117 having a
circular planar shape, a cover 120 having a circular planar shape and a lid, and the cover 120 as
main components. The microphone unit 116 provided in the base 117, the cord insertion hole
125 communicating the outside with the internal space covered by the cover 120 and the
external connection cord introduced from the cord insertion hole 125 at the central position of
the planar shape of the base 117 123, a rubber plate 122 provided at the lower part of the base
117, and a tube shaft 124 fitted in the cord insertion hole 125.
[0010]
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The base 117 has a cord insertion hole 125 communicating the outside with the internal space
covered by the cover 120, and this cord insertion hole 125 is formed at the intersection of the
central axes of the three microphone units 116 arranged radially. It is done. The base 117 is
made of flat metal, and a rubber plate 122 provided on the lower surface thereof is used as a
support. The cover 120 is pressed in the inner diameter direction by the pressing member 121.
Furthermore, an insertion hole for a screw 113 is provided at the center of the planar shape of
the cover 120, and the screw 113 is screwed from the screw hole into an appropriate screw hole
provided on the tube shaft 124, thereby the cover 120. Is fixed to the base 117. Further, on the
upper surface of the base 117, a circuit board (not shown) is present.
[0011]
As described above, the outer appearance of the boundary microphone is mainly composed of
the three components of the base 117, the cover 120, and the pressing member 121, and the
built-in components are incorporated in the internal space thereof. However, in the conventional
circular boundary microphone, since the cover 120 is perforated by the punching plate, the
cover 117 and the base 120 are in point contact in practice and there is a gap, which causes a
problem in the shielding effect. was there. In addition, when the screw 113 is loosened, the cover
120 and the base 117 become floating, and there is a problem that the conduction between the
both can not be secured and the shielding effect becomes unstable.
[0012]
JP, 2009-100157, A
[0013]
According to the present invention, a structure in which no gap is formed at the boundary
between the cover and the base prevents the leakage of the shield against the electromagnetic
wave, thereby reliably preventing the penetration of the electromagnetic wave, and a member for
the electromagnetic wave shield such as a metal mesh. It is an object of the present invention to
provide a boundary microphone whose cost can be reduced by not using.
[0014]
A boundary microphone according to the present invention comprises a base made of metal, a
cover made of metal and having a plurality of holes through which sound waves are introduced, a
microphone unit disposed on the base and converting sound into an electrical signal, and the
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cover A pressing member for pressing the base, the cover having a collar at the periphery, the
pressing member pressing the collar of the cover toward the base to press the collar of the cover
on the base The most important feature is the surface contact.
[0015]
According to the present invention, the connection between the base made of metal and the
cover can be made without a gap, and electromagnetic waves entering from the outside toward
the built-in component can be blocked more effectively.
Also, the generation of noise due to the electromagnetic waves can be prevented, and the
shielding effect can be further enhanced.
There is also a cost reduction effect because it is not necessary to provide a shield member
inside.
[0016]
It is an exploded sectional view showing an example of a boundary microphone concerning the
present invention.
It is sectional drawing of the said Example. It is a top view which shows the said Example in the
state which removed the cover. It is a bottom view of the said Example. It is a bottom view which
shows the different operation ¦ movement aspect of the said Example. FIG. 6 is a top view
showing the operation mode shown in FIG. 5 of the above embodiment in accordance with FIG. It
is a top view which shows the cover in the said Example. It is a top view which shows the usage
condition of the said Example typically. It is a top view which shows typically another usage
aspect of the said Example. It is a top view which shows typically another usage condition of the
said Example. It is sectional drawing which shows the prior art example of a boundary
microphone. FIG. 6 is an exploded cross-sectional view showing a conventional example of a
circular boundary microphone. It is sectional drawing of the said conventional boundary
microphone.
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[0017]
Hereinafter, embodiments of the boundary microphone according to the present invention will be
described with reference to the drawings. In FIG. 1 to FIG. 3, the boundary microphone according
to the present embodiment is formed in a flat circular dish shape and has a cover 1 having a flat
ridge 1a at the outer peripheral edge of the open end thereof; A microphone unit holder that
holds the base 2 having a circular planar shape, the ring-shaped pressing member 5, the three
microphone units 3, and the two microphone units 3 among them and is slidably incorporated in
the base 2 6, the knob 14 provided on the lower surface of each microphone unit holder 6, the
circuit board 9 shown in FIG. 3, and the knob 14 of the microphone unit holder 8 provided on
the base 2 for penetrating the base 2 And a hole 11 for connecting the internal space covered by
the cover 1 to the outside at the central position of the planar shape of the base 2 and the lower
part of the base 2 A pedestal 7 provided, the fitted tube axis 6 to the code insertion hole 11, the
connecting cord 4 with the outside is inserted into the tube axis 6, it is mainly composed of a
wire 12.
[0018]
In FIG. 2, the ring-shaped pressing member 5 presses the flange portion 1 a of the cover 1 all
around. The pressing member 5 has a convex portion 5a for pressing the collar portion 1a on the
lower surface which is a surface opposite to the collar portion 1a of the cover 1, and the ridge
portion 1a of the cover 1 is formed by the convex portion 5a. Are pressing towards. The convex
portion 5 a is continuously formed over the entire circumference of the pressing member 5. The
base 2, the cover 1 and the pressing member 5 are integrally fastened by a fastening member 13
composed of a screw or the like.
[0019]
By configuring the boundary microphone in this manner, the junction between the metal base 2
and the cover 1 is in surface contact, and it is possible to make no gap around the periphery.
Furthermore, the pressing member 5 presses the cover 1, and the flange portion 1 a of the cover
1 and the upper surface of the outer peripheral portion of the base 2 can be strongly fixed.
Furthermore, since the pressing force by the pressing member 5 is concentrated on the flange
portion 1a of the cover 1 by the convex portion 5a, the flange portion 1a of the cover 1 may be
in surface contact with the upper surface of the outer peripheral portion of the base 2 strongly
and without gap. it can. In this way, it is possible to more effectively block the electromagnetic
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wave that is going to enter the built-in part from the outside, and the shielding effect can be
further enhanced to prevent the generation of noise due to the electromagnetic wave. In addition
to this, since it is not necessary to provide a shield member inside, the cost can be reduced that
much.
[0020]
In FIG. 2, a cylindrical tube shaft 6 is fitted in the cord insertion hole 11 of the base 2, and an
external connection cord 4 is inserted in the tube shaft 6. As shown in FIG. 3, three microphone
units 3 are disposed around the tube axis 6 with the sound collecting surface directed radially
outward of the base 2. Two of the three microphone units 3 are held by the microphone unit
holder 8. These microphone unit holders 8 are incorporated slidably along a circular arc surface
6 a formed on the tube axis 6 centering on the cord insertion hole 11 and drawing a circular arc
on the surface of the base 2. Therefore, the two microphone units 3 held by the microphone unit
holder 8 can also move along with the microphone unit holder 8 while drawing a circular arc in a
certain angle range around the cord insertion hole 11. The remaining one microphone unit 3 is
fixed to the base 2. The cases of the two microphone units 3 are conducted to the base 2 through
the microphone unit holder 8, and the cases of the other one microphone unit 3 are conducted
directly to the base 2 without the microphone unit holder 8. . Further, since each microphone
unit holder 8 rotates while contacting with the arc surface 6 a of the tube shaft 6, even when the
microphone unit 3 is moved, the conduction between the case of the microphone unit 3 and the
base 2 can always be ensured. .
[0021]
As in the above embodiment, by passing the cord 4 from the tube axis 6 toward the lower side of
the base 2, the cord 4 is retracted from the sound collection range of each microphone unit 3,
and the sound from the surroundings is efficiently picked up be able to. The slide method of the
microphone unit 3 is not limited to the configuration shown in the drawing, and an appropriate
one can be selected. For example, a member for assisting the slide may be used.
[0022]
The three microphone units 3 are arranged such that their central axes are parallel to the plane
of the base 2. Further, in a moving aspect of the two movable microphone units 3, they are
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arranged radially at intervals of 120 degrees around the cord insertion hole 11. The two
microphone unit holders 6 hold the microphone unit 3 so as to maintain the above angle. As
shown in FIGS. 1 and 2, a knob 14 is integrally provided on the lower surface of the microphone
unit holder 6. The knob 14 is integrally provided with the microphone unit holder 6 by an
appropriate means such as integral molding or bonding with the microphone unit holder 6. The
base 2 has two holes 10 through which the knobs 14 of the microphone unit holder 8 pass.
These holes 10 are for guiding the movement of the microphone unit holder 8 centering on the
cord insertion hole 11, and have a circular arc shape centering on the code insertion hole 11 and
the movement range of the microphone unit holder 8 It is formed in a certain range in order to
regulate.
[0023]
As shown in FIG. 4, the hole 10 is formed in a slit shape so as to draw an arc centered on the
cord insertion hole, and the knob 14 is moved from the lower surface of the base 2 within the
range of the hole 10. Thus, the microphone unit holder 8 can be moved together with the
microphone unit 3. Thus, the hole 10, the microphone unit holder 8 and the knob 14 constitute
microphone unit arrangement changing means.
[0024]
The number of microphone units 3 provided in the boundary microphone according to the
present invention, the number of microphone unit holders 6, and therefore the number of
microphone unit arrangement changing means are also arbitrary. For example, three microphone
units 3 are respectively held by the microphone unit holder 6 and arranged radially on the base
2, and only one microphone unit or all three microphone units are provided with arrangement
changing means. It is also good. The number of holes 10 is provided in accordance with the
number of microphone unit arrangement changing means. The knob 14 may be integrally
formed with the microphone unit holder, or may be fixed by an adhesive or the like.
[0025]
As shown in FIG. 4, when the two knobs 14 are located at one end of each hole 10 formed in the
base 2, more specifically, the knob 14 on the right side in FIG. When the left knob 14 is at the
clockwise limit position around the cord insertion hole 11 at the counterclockwise limit position
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as shown in FIG. 3, the positional relationship of the three microphone units 3 in the
circumferential direction is 120 as shown in FIG. Degree interval. Further, as shown in FIG. 5,
when the knob 14 is located at the other end of the hole 10 of the base 2, as shown in FIG. 6, two
microphones held by two microphone unit holders 8 respectively The microphone unit
arrangement changing means is designed such that the units 3 are spaced 180 degrees in the
circumferential direction, so that the central axes of the two microphone units 3 are in a straight
line. Further, when the two microphone units 3 respectively held by the microphone unit
arrangement changing means are spaced by 180 degrees in the circumferential direction, as
shown in FIG. 6, the other one microphone unit 3 has its center The axis is arranged at 90
degrees with respect to a line connecting the centers of the two microphone units 3.
[0026]
Circuit boards 9 identical to the number of microphone units 3 are fixed on the base 2 and
between the microphone units 3. The microphone unit 3, the circuit board 9, and the cord 4 are
electrically connected by the appropriate wiring 12, and can be electrically connected to an
external output and can be supplied with power. The boundary microphone configured as
described above can easily adjust the sound collection possible range by operating the knob 14
that constitutes the microphone unit arrangement changing means. Although the arrangement of
the circuit board 9 and the wiring 12 is optional, the arrangement is made so as not to hinder the
movement of the microphone unit holder 6. For example, when there are three microphone units
3 as in the illustrated embodiment, it is preferable to arrange three circuit boards 9 radially
around the cord insertion hole 11 as shown in FIG.
[0027]
The cover 1 covers the top surface of the base 2 including the microphone unit 6 and the circuit
board 9 as described above. The cover 1 is made of a metal part in the same manner as the base
2, and an infinite number of openings are formed to guide the sound wave to the microphone
unit 3. Further, the cover 1 is made of punched metal in which innumerable holes are formed by
punching, and the cover 1 is placed on the upper surface of the base 7 in a state of being put
down. As shown in FIG. 7, notches 1 b are formed in a plurality of places in the flange portion 1 a
of the cover 1 in order to pass the fastening member 13. As shown in FIG. 3, the receiving
portion 2a of the flange portion 1a of the cover 1 is formed on the upper surface side of the base
2 having a circular planar shape, and the peripheral portion of the cover 1 is designed to be
easily in contact with the base 2. ing. The shape and the material of the cover 2 are not limited to
the above shapes and materials, and if an infinite number of openings for guiding sound waves to
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the microphone unit are formed, an appropriate shape and material can be selected.
[0028]
As described above, the collar 1 a of the cover 1 is formed on the entire outer periphery of the
cover 1. The cover 1 is painted on the surface. However, the contact surface of the cover 1 with
the base 2, that is, the bottom surface of the cover 1 is an unpainted surface, and the cover 1 and
the base 2 are electrically connected. The said to-be-coated surface may be formed by not setting
it as a coating object surface in a coating process, and may be formed by removing coating, after
coating the whole surface. The planar shape of the cover 1 and the base 2 is not limited to a
circular shape, but may be appropriately selected, and may be a square shape or a triangular
shape.
[0029]
The ring-shaped pressing member 5 presses the flange portion 1 a of the cover 1 all around. As
shown in FIG. 1, the pressing member 5 has a convex portion 5 a that presses the collar portion
1 a on the surface facing the collar portion 1 a of the cover 1. The convex portion 5 a has a
semicircular cross section, and is formed over the entire circumference of the pressing member
5. As a cross-sectional shape of the said convex part 5a, an appropriate thing can be selected.
Further, the convex portion 5a may extend over the entire circumference of the pressing member
5 as described above, or may be formed intermittently. In consideration of the effect of the
pressing, it is preferable to form the entire circumference because the pressure spreads to the
entire circumference. The base 2, the cover 1 and the pressing member 5 are integrally fastened
by an appropriate fastening member 13. In the case of a normal boundary microphone, a
condenser microphone unit having an impedance converter is used as the microphone unit 6.
Although not shown, the circuit board 9 incorporates a sound quality adjustment circuit, an audio
output circuit, the above-mentioned impedance converter, and the like.
[0030]
As shown in FIG. 6, when the two microphone units 3 respectively held by the two microphone
unit holders 8 are spaced 180 degrees in the circumferential direction, the direction of the other
one microphone unit 3 is The angle is 90 degrees with respect to a line connecting the centers of
the two microphone units 3. Therefore, it is assumed that a boundary microphone 16 in which
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another one microphone unit 3 not having the microphone unit holder 8 is turned off is installed
on the table as shown in FIG. Since only the two microphone units 2 arranged in a back-to-back
manner at an interval of 180 degrees perform electroacoustic conversion operation, sound waves
of the boundary microphone 16 before and after the boundary microphone 16 You can pick it
up. Therefore, it is preferable to arrange the boundary microphone 16 set as described above at
the center of the table 15 in the front-rear direction, for example, when an attendee is seated in
front of or behind the table 15 to hold a meeting.
[0031]
In FIG. 9, the two microphone units 3 respectively held by the microphone unit holder 8 as
described above are set to have an interval of 180 degrees in the circumferential direction, and 3
including the other microphone unit 3 as well. An example of use in case this microphone unit is
in an ON state is shown. The two microphone units 3 separated by 180 degrees from each other
and the other microphone unit 3 in the direction orthogonal to the central axis of these
microphone units 3 respectively have a sound collection range. Therefore, for example, when a
conference is conducted by surrounding table 15 as shown in FIG. 9, if boundary microphone 16
set as described above is installed at the end of table 15, with attendees located before and after
table 15 It is possible to pick up the remarks of the attendees located on the side of the table 15.
[0032]
As shown in FIG. 3, when the three microphone units 3 are radially arranged at intervals of 120
degrees centering on the cord insertion hole 11, as shown in FIG. It can sound. Therefore, it is
possible to pick up the voices of all the people seated around the table 15.
[0033]
The adjustment of the sound collection range can be easily and anyone can adjust from the
outside of the boundary microphone 16 by the microphone unit arrangement changing means. If
it is not possible to adjust the sound collection range unless the cover 1 is removed, the built-in
parts may be touched to cause a failure. In that respect, according to the illustrated embodiment,
since the adjustment can be made from the outside, the user can easily adjust the optimum sound
collection direction while avoiding causes such as a failure inside the boundary microphone.
Therefore, the maintenance cost can be reduced by eliminating the complexity that can be
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adjusted only by a specialized engineer.
[0034]
The boundary microphone according to the present invention is not limited to the configuration
of the embodiment described above. The microphone unit 3 inside the cover 1 and the base 2 of
the boundary microphone may be covered with a shield member such as a metal mesh. In
addition, by adding an appropriate speaker unit to the internal configuration, a single speakerequipped boundary microphone can be provided which simultaneously has a sound collecting
function and a speaker function. Can.
[0035]
Reference Signs List 1 cover 2 base 3 microphone unit 4 external code 5 pressing member 6
tube axis 7 base 8 microphone unit holder 9 circuit board 10 hole 11 code insertion hole 12
wiring 13 fastening member 14 knob
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