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JP2000032584

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DESCRIPTION JP2000032584
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
unidirectional microphone, and more particularly, to a unidirectional microphone used by being
incorporated in a display panel or the like for a personal computer (PC). .
[0002]
2. Description of the Related Art With the spread of the Internet, recently, not only text
information but also images and sounds have traveled over the Internet as personal information.
E-mail is no exception, and it is becoming easier to send photos and voices to acquaintances by
improving the operability of software.
[0003]
[0003] Therefore, in order to easily capture voice information as data of a personal computer,
one in which a microphone is incorporated in advance into a personal computer body or a
display has been developed. In particular, laptop type portable terminals are becoming more
rapidly popular.
[0004]
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By the way, when a microphone is incorporated into a personal computer body or a display, the
sound pressure gradient can not be obtained because the mounting surface is often relatively
flat.
[0005]
For this reason, a non-directional condenser microphone is used exclusively for this type of builtin microphone, but since it is non-directional, the difference between the ambient noise and the
target sound is small and it is often difficult to hear. And inconveniences such as difficulty in
speech recognition.
[0006]
There is a boundary microphone as a microphone attached to a plane and used.
According to this microphone, since the main axis of the microphone unit is parallel to the plane
which is the mounting surface, the paths to the front acoustic terminals of the direct sound and
the reflected sound from the plane become almost the same, It is possible to prevent the loss of
clarity due to the phase difference.
[0007]
However, since the boundary microphone is mainly placed on a desk and the main axis side of
the microphone unit is directed to the speaker, it is not suitable for being incorporated into a
personal computer or the like.
[0008]
In order to pick up a target sound, a unidirectional microphone may be used. For example, when
attaching it to a personal computer body or a display, it is preferable to use the microphone in
view of its appearance and the like. It is required to incorporate it so that it does not stand out.
[0009]
Therefore, a recess is provided in a flat surface of a display or the like, and a unidirectional
microphone unit is mounted so as to be embedded in the recess. In this case, the front and rear
acoustic terminals and There is a problem that the sound pressure difference disappears during
the period, and although it is unidirectional, it does not operate at the sound pressure gradient,
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and it becomes close to non-directional.
[0010]
The present invention has been made to solve such problems, and its object is to provide a
single-pointing system even if it is incorporated in a plane of a personal computer body or a
display etc. so as to be flush with it. It is an object of the present invention to provide a
unidirectional microphone in which the gender is not lost.
[0011]
SUMMARY OF THE INVENTION In order to achieve the above object, the present invention
comprises a microphone unit having a front acoustic terminal and a rear acoustic terminal, and is
flat such as an outer frame of a computer display panel. In a unidirectional microphone
incorporated in a wall and used, a unit storage portion having a diameter larger than the
microphone unit and a depth larger than the axial length is formed on the wall side, The
microphone unit is housed in the unit housing portion so that the front acoustic terminal is
positioned in a plane including the wall surface, and is fitted in the opening surface of the unit
housing portion on the front acoustic terminal side of the microphone unit And a side acoustic
terminal connected to the rear acoustic terminal is formed around the baffle plate. To have.
[0012]
According to this configuration, the sound wave from the sound source is captured at the front
acoustic terminal and enters the unit storage section from the side acoustic terminal to reach the
rear acoustic terminal, so that a sound pressure gradient occurs between the two. Unidirectional
characteristics are obtained.
[0013]
In the present invention, the baffle plate may be substantially smaller than the opening surface of
the unit housing portion to provide an air leakage passage therebetween, and the air leakage
passage may be the side acoustic terminal. Preferably, this allows the side acoustic terminals to
be provided with a minimum number of processing steps.
[0014]
On the other hand, a through hole may be formed around the baffle plate, and the through hole
may be used as the side acoustic terminal, and such an embodiment is also included in the
present invention.
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[0015]
In the present invention, preferably, the side acoustic terminals are arranged symmetrically with
respect to the front acoustic terminal.
According to this, when the sound source of the spherical wave is far, the sound wave of the
same phase arrives at the front acoustic terminal and the side acoustic terminal, so only the
nondirectional component of the unidirectional microphone unit has sensitivity. It will bring.
[0016]
However, since the sound pressure incident on the microphone decreases in inverse proportion
to the distance from the sound source, noise from a distance can be made to have a low level.
On the other hand, when the speaker approaches, the phase difference due to the spherical wave
from the adjacent sound source is generated between the front acoustic terminal and the side
acoustic terminal, so that the microphone unit operates as unidirectionality. .
[0017]
On the other hand, the side acoustic terminals may be disposed asymmetrically with respect to
the front acoustic terminals, whereby acoustic directivity with respect to the main axis (directing
axis) of the unit can be obtained. The axis of can be offset.
That is, while the main axis of the microphone unit is perpendicular to the plane, it is possible to
tilt the axis of acoustic directivity in a predetermined direction (for example, the speaker
direction).
[0018]
In the case where the wall surface is an outer frame of a computer display panel, a stereo
microphone can be easily formed by arranging the unidirectional microphones as a pair on the
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left and right.
[0019]
Further, according to the present invention, by providing a waterproof film covering the opening
surface of the unit storage portion on the wall surface, waterproofing is achieved without taking
waterproofing means separately for the front acoustic terminal and the rear acoustic terminal.
Can be a microphone.
[0020]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be
described in more detail based on the embodiments shown in the drawings.
[0021]
FIG. 1 shows a first embodiment in which the unidirectional microphone 1 according to the
present invention is applied to a laptop computer COM.
That is, the laptop computer COM includes a keyboard unit B as a personal computer main body
having a predetermined key arrangement and a display panel unit A foldable with respect to the
keyboard unit B. The microphone 1 is a display panel unit. At a predetermined position of the
outer frame F of the liquid crystal display panel M in A, the same frame F is provided on the same
plane.
[0022]
Here, referring to FIG. 2 (a) as a plan view of the main part of the portion of the microphone 1
from FIG. 1 and FIG. 2 (b) which is a sectional view taken along the line A-A, the microphone 1
The microphone unit 2 is unidirectional, and although not shown in detail, a portion indicated by
reference numeral 21 is a front acoustic terminal, and a portion indicated by reference numeral
22 is a rear acoustic terminal. .
[0023]
On the outer frame F side, a unit storage portion F1 having a diameter larger than that of the
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microphone unit 2 and a depth larger than its axial length is provided.
In this embodiment, the unit storage portion F1 is formed as a bowl-shaped circular recess.
[0024]
Assuming that the main axis (orientation axis) passing through the center of the front acoustic
terminal 21 in the microphone unit 2 is X, the microphone unit 2 is arranged so that its main axis
X is perpendicular to the plane F2 of the outer frame F. It accommodates in the accommodating
part F1.
In this case, the microphone unit 2 is a central portion of the unit storage portion F1 by a
suitable support means (for example, a rubber damper etc.) not shown, and its front acoustic
terminal 21 is in the circular opening surface of the unit storage portion F1. It is supported to be
located at
[0025]
A disk-shaped baffle plate 3 fitted on the front acoustic terminal 21 side of the microphone unit
2 so as to be flush with the plane F2 of the outer frame F in the circular opening surface of the
unit storage portion F1. Is provided integrally.
[0026]
In this embodiment, the baffle plate 3 has a diameter slightly smaller than the opening surface of
the unit storage portion F1, whereby an air leakage portion is annularly formed at the periphery
of the baffle plate 3 and the air leakage portion is The side acoustic terminal 4 is in
communication with the rear acoustic terminal 22.
[0027]
The baffle plate 3 is sized to fit airtightly in the opening surface of the unit storage portion F1,
and through holes are formed at the periphery of the baffle plate 3 preferably at equal intervals,
and the through holes are formed. It may be a side acoustic terminal.
[0028]
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In the first embodiment, the unit storage portion F1 is formed into a bowl-shaped circular recess,
but this is deformed into a bowl-shaped recess having a rectangular shape in a plan view as
shown in FIG. 3 (a). You may
In addition, FIG.3 (b) is the sectional view on the AA line of Fig.3 (a).
[0029]
In this modification, the baffle plate 3 is also a rectangular plate fitted in the rectangular opening
surface of the unit storage portion F1 and side acoustics communicated with the rear acoustic
terminal 22 at both end positions in the longitudinal direction thereof. Terminals 4, 4 are
provided.
[0030]
Here, the operation principle of the unidirectional microphone unit 2 will be described with
reference to the schematic view of FIG. 4, and then the operation of the above embodiment will
be described based on the schematic views of FIG. 5 and FIG.
[0031]
In FIG. 4, assuming that the distance between the sound source P0 and the microphone unit 2 is
r, and a spherical wave of sound pressure from P0 ejωt is generated from the sound source P0,
the sound pressure P1 of the front acoustic terminal 21 is , P1 = (P0 / r) ejω (t− (r / c)), whereas
the sound pressure P2 of the rear acoustic terminal 22 is P2 = (P0 / (r + d cos θ)) ejω (t− (t− (
r / c)-(d cos θ / c)).
In the above equation, c is the velocity of sound, d is the distance between the acoustic terminals,
and θ is the incident angle of the sound wave to the front acoustic terminal 21.
A single directivity is obtained by the sound pressure difference between the sound pressure P1
and the sound pressure P2.
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However, the condition is that r> d.
[0032]
Next, the state when the sound source P0 is located in front of the microphone 1 of the first
embodiment and a spherical wave comes from the sound source P0 will be described with
reference to the schematic view of FIG.
Here, the inter-terminal distance from the main axis X (the position of the front acoustic terminal
21) of the microphone unit 2 to the side acoustic terminals 4 and 4 is d1, and the left side with
respect to the sound pressure P1 of the front acoustic terminal 21. The sound pressure of the
side acoustic terminal 4 located on the side is P2L, and the sound pressure of the side acoustic
terminal 4 located on the right side is P2R.
[0033]
Since the sound wave from the sound source P0 is a spherical wave, a phase delay distance l
occurs in each of the side acoustic terminals 4 and 4 with respect to the front acoustic terminal
21.
The phase delay distance l decreases as r increases, that is, as the distance to the sound source
P0 increases.
Also, the smaller the inter-terminal distance d1, the smaller.
[0034]
Therefore, when the sound source P0 is at a distance from the microphone unit 2, the sound
pressure P1, the sound pressure P2L and the sound pressure P2R are substantially in phase, so
this unidirectional microphone unit 2 Only the non-directional component of will provide
sensitivity.
[0035]
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However, since the incident sound pressure to the microphone 1 becomes smaller in inverse
proportion to the distance r from the sound source P0, the noise from a distance becomes a low
level, and there is no particular problem.
On the contrary, when the speaker (sound source) approaches, a phase difference due to a
spherical wave from the adjacent sound source is generated between the front acoustic terminal
21 and the side acoustic terminals 4 and 4, so the microphone unit 2 Works as uni-directional.
[0036]
Next, the case where the sound source P0 is located in the oblique direction with respect to the
microphone unit 2 and the spherical wave comes from the sound source P0 will be described
with reference to the schematic view of FIG.
In this case, a sound wave having a sound pressure P2R arrives at the right side acoustic terminal
4 earlier than the front acoustic terminal 21 and the left side acoustic terminal 4, but this sound
wave (sound pressure P2R) The rear acoustic terminal 22 is virtually positioned on the main axis
X of the microphone unit 2 because it is combined (mixed) with the sound wave (sound pressure
P2L) from the left side acoustic terminal 4 in the air chamber in the part F1. Thereby,
unidirectionality is obtained also by the sound waves incident on the same plane F2.
[0037]
That is, as shown in FIG. 6, when the sound wave is incident on the microphone unit 2 in an
oblique direction, the sound wave incident on the front acoustic terminal 21 and the sound wave
incident on the side acoustic terminal 4 Since there is a phase difference corresponding to the
difference in distance, a single directivity can be obtained.
[0038]
In practice, a mortar-like recess having a rectangular opening surface of 2 cm in width and 7 cm
in length as described in the modification of FIG. 3 is formed in a flat plate of 18 cm long and 25
cm wide, and A microphone was made by housing a unidirectional electret condenser
microphone unit, attaching a baffle plate to the front acoustic terminal side, and providing a side
acoustic terminal with a width of about 4 mm at both ends of the baffle plate. .
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[0039]
When the sound pickup characteristics were measured, it was confirmed that good unidirectivity
was maintained up to the low range, as shown in FIG.
In addition, when the polar pattern was measured, as shown in FIG. 8, a hypercardioid curve
specific to a unidirectional microphone was obtained.
[0040]
Next, a second embodiment of the present invention shown in FIG. 9 will be described.
9 (a) is a plan view of the main part similar to FIG. 3 (a) described above, and FIG. 9 (b) is a
sectional view taken along the line A-A.
[0041]
In the second embodiment, when the microphone unit 2 is housed in the unit housing portion F1,
the acoustic pointing axis X1 is set as the main axis while the main axis X is made perpendicular
to the plane F2 of the outer frame F. In order to shift from X, the side acoustic terminals 4 are
arranged asymmetrically with respect to the front acoustic terminals 21.
[0042]
That is, in the second embodiment, the unit storage portion F1a has a shape obtained by
removing one side (the left side portion in FIG. 3) of the unit storage portion F1 consisting of a
mortar-like recess having a rectangular shape in a plan view The microphone unit 2 is housed so
that its main axis X is perpendicular to the plane F2 of the outer frame F at a position from one
side of the unit housing portion F1a.
[0043]
Also in the second embodiment, the baffle plate 3 fitted in the rectangular opening surface of the
unit storage portion F1a is attached to the front acoustic terminal 21 side of the microphone unit
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2, and the end of the baffle plate 3 is attached. A side acoustic terminal 4 communicating with
the rear acoustic terminal 22 of the microphone unit 2 is formed in the portion.
[0044]
According to the microphone unit 2, as described above, the directivity (the sound pressure
gradient) between the front acoustic terminal 21 and the rear acoustic terminal 22 can be
obtained by unidirectionality. In the second embodiment, the side acoustic terminal 4 is provided
only on one side as viewed from the front acoustic terminal 21 so that the acoustic pointing axis
X1 with respect to the main axis X of the microphone unit 2 is as shown in FIG. In (b), it is shifted
counterclockwise by a predetermined angle.
[0045]
FIG. 10 shows a polar pattern in the case where the side acoustic terminal 4 is provided at a
position about 1 cm away from the front acoustic terminal 21 on one side. It can be seen that the
acoustic pointing axis X1 is offset by about 15 degrees with respect to the main axis X.
[0046]
As described above, by making it possible to shift the acoustic directional axis X1 by a
predetermined angle with respect to the main axis X of the microphone unit 2, especially in a
personal computer or the like in which the mounting location of the microphone is limited, It is
possible to turn directivity in the direction of the mouth of the person (user).
Although the rectangular baffle plate is used in the second embodiment, a semicircular baffle
plate may be provided by halving the disk-like one as in the first embodiment.
[0047]
Further, according to the present invention, the microphone 1 can be easily waterproofed.
FIG. 11 (a) is a plan view of the third embodiment, and FIG. 11 (b) is a sectional view taken along
the line AA.
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[0048]
That is, by providing the waterproof frame 6 around the unit storage portion F1 and stretching
the waterproof film 5 on the waterproof frame 6, the microphone 1 can be waterproofed.
[0049]
Incidentally, in the past, the front acoustic terminal 21 and the rear acoustic terminal 22 had to
take waterproofing means such as waterproof films, respectively. According to the third
embodiment, the front acoustic terminal 21 and the rear acoustic terminal 22 have the same
structure. Since the side acoustic terminals 4 are on the same plane F2, the waterproof film 5
only needs to be provided on the plane F2, so that waterproofing can be performed easily and
inexpensively.
[0050]
In each of the above embodiments, the display panel portion of the personal computer is
illustrated as a plane to which the unidirectional microphone unit is attached. However, the
present invention is not limited to this, and the mounting thereof is not limited thereto. The flat
surface may be a personal computer body or may be a flat portion of another electronic device
(electric device).
[0051]
As described above, according to the present invention, the following effects can be achieved.
It becomes possible to give good single directivity to a microphone unit attached as the same
plane on a flat surface part such as a PC main body or its display, and thereby the target sound
can be picked up well even in the presence of ambient noise. be able to.
[0052]
Also, by arranging the side acoustic terminals asymmetrically with respect to the front acoustic
terminals, the axis of acoustic directivity can be offset with respect to the main axis of the unit.
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That is, while the main axis of the microphone unit is perpendicular to the plane, it is possible to
tilt the axis of acoustic directivity in a predetermined direction (for example, the speaker
direction).
For this reason, particularly in a personal computer or the like in which the mounting location of
the microphone is limited, directivity can be diverted in the direction of the mouth of the speaker.
[0053]
The microphone unit to be used does not have to be a special unit, and a commonly used
inexpensive microphone unit of, for example, a unidirectional electret condenser type can be
used.
[0054]
In addition, parts such as baffle plates can be obtained at low cost, and the overall configuration
is simple, so that they can be assembled at low cost.
Furthermore, the microphone can be easily waterproofed.
[0055]
Brief description of the drawings
[0056]
1 is a perspective view showing a use state of the microphone according to the first embodiment
of the present invention.
[0057]
2 is a plan view of the microphone according to the first embodiment and a sectional view taken
along the line A-A.
[0058]
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3 is a plan view showing a modification of the first embodiment and a sectional view taken along
the line A-A.
[0059]
4 is a schematic diagram for explaining the operation principle of the unidirectional microphone
unit.
[0060]
5 is a schematic diagram for explaining the operation of the microphone according to the first
embodiment when the sound source is in the front direction of the microphone unit.
[0061]
6 is a schematic diagram for explaining the operation of the microphone according to the first
embodiment when the sound source is in the oblique direction of the microphone unit.
[0062]
7 is a characteristic graph obtained by measuring the directivity of the microphone according to
the modification of FIG.
[0063]
8 is a characteristic graph obtained by measuring the polar pattern of the microphone according
to the modification of FIG.
[0064]
9 is a plan view of a microphone according to a second embodiment of the present invention and
a sectional view along line AA thereof.
[0065]
10 is a characteristic graph obtained by measuring the polar pattern of the microphone
according to the second embodiment.
[0066]
FIG. 11 is a plan view of a microphone according to a second embodiment of the present
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invention and a sectional view along line AA thereof.
[0067]
Explanation of sign
[0068]
Reference Signs List 1 microphone 2 microphone unit 21 front acoustic terminal 22 rear acoustic
terminal 3 baffle plate 4 side acoustic terminal (air leakage passage) 5 waterproof film 6
waterproof frame A monitor unit B keyboard unit COM computer F outer frame F1 concave
portion F2 plane
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