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JP2004080173

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JP2004080173
The present invention provides a microphone that can exhibit high directivity and can be
miniaturized. A support (2) is provided with a sound collection unit (2A) at the center thereof,
and a reflection member (20) is provided at the front of the outside. The vibrating member 10
provided in the sound collecting unit 2 </ b> A is supported by a cover member 11 supported on
the front side of the support 2. An introduction passage 13 is formed between the vibrating
member 10 and the reflecting member 20. The sound wave S3a directly incident from the front
side of the vibrating member 10 is reflected by the reflecting surface 20a and is canceled by the
reflected sound wave S3b incident from the back side of the vibrating member 10 through the
introduction path 13. Thus, the vibration of the vibrating member 10 is suppressed. [Selected
figure] Figure 3
Directional microphone
TECHNICAL FIELD [0001] The present invention relates to a directional microphone that is most
sensitive to sound incident from the front, and can be made less sensitive to sound from other
directions. [0002] As a conventional directional microphone, there is a microphone type in which
a long and narrow sound collecting portion is provided in a pipe shape at a tip end portion. In
this gun type, for example, a sound collecting unit is mounted on the back side (base end side) of
the pipe-like portion. Also, a plurality of holes are formed on the side surface of the pipe portion,
and the sound entering from the hole on the side surface escapes from the other holes formed on
the side surface, so that the sound does not reach the sound collecting portion less The
sensitivity can be lowered. In addition, a hole is also formed in the front of the pipe-like portion,
and the sound that has entered straight from the hole in the front does not get out of the hole in
the side, and the sound reaches the sound collecting portion and the sensitivity can be increased.
Another microphone is one having a reflecting surface formed by a paraboloid called parabola
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type. In this type of microphone, a sound collection unit is provided in front of the paraboloid,
and in particular, sound incident from the front is collected in the sound collection unit, so
sensitivity to smaller sounds is high. can do. SUMMARY OF THE INVENTION However, although
the microphones of the above-mentioned conventional gun type and parabola type can improve
the sensitivity to the sound from a certain direction in any case, In the gun type, the length
dimension of the pipe part is increased, and in the parabola type, sufficient directivity can not be
exhibited unless the diameter dimension of the reflecting surface is increased, and it is difficult to
miniaturize the apparatus. there were. The present invention is intended to solve the abovedescribed conventional problems, and it is an object of the present invention to provide a
directional microphone that can exhibit compactness and high directivity. According to the
present invention, there is provided a directional microphone provided with a sound collecting
unit for vibrating a vibrating member with a sound generated in a certain direction outside and
converting it into a sound signal. The sound collecting unit is provided on a support, and the
support is provided with a reflecting member for guiding a sound generated at a position
deviated from the predetermined direction so as to be incident from the back side of the
vibrating member, A direct sound wave generated at a position deviated from a predetermined
direction and directly incident on the front side of the vibrating member is applied with a
reflected sound wave incident from the back side of the vibrating member so as not to operate
the sound collecting unit or suppressed. It is characterized by the fact that
In the present invention, for example, with respect to the sound incident from the direction
inclined to the front of the vibrating member, the sound pressure by the direct sound wave
directly incident on the front side of the vibrating member is reflected by the reflection member
Since the sound pressure of each other is canceled by the sound pressure by the reflected sound
wave incident from the back side of the vibrating member, the vibrating member is not vibrated,
or the mutual sound pressure is suppressed and the force of vibrating the vibrating member is
weakened. Be In this way, since it is possible to cancel or suppress sound incident from directions
other than the front, it is possible to obtain a compact and highly directional microphone. For
example, the vibrating member is supported in front of the reflecting member, and an
introduction path is formed between the vibrating member and the reflecting member for
guiding the reflected sound wave to the back side of the vibrating member. . With such a
configuration, for example, sound incident from a direction other than the front can be easily
guided to the rear surface of the vibrating member. In this case, the reflecting member may be
formed of a surface including at least one of a flat surface and a curved surface. FIG. 1 is a plan
view of a directional microphone according to the present invention as viewed from the front,
FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1, and FIG. 4 is a partial enlarged
cross-sectional view of FIG. 2 showing FIG. As shown in FIG. 1, the directional microphone 1 of
the present embodiment has a support 2 formed in a cylindrical shape of a synthetic resin
material. The support 2 is formed with a circular recess 2a whose front (Z1 side) is open, and a
sound collecting unit 2A functioning as a microphone is provided in the recess 2a. In the sound
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collecting portion 2A, a ring-shaped rear yoke 3 is fixed to the bottom (Z2 side in FIG. 2) of the
recess 2a, and a cylindrical inner yoke 4 is at the center of the rear yoke 3 It is integrally formed
with 3. The tip of the inner yoke 4 is formed so as to extend beyond the front end face of the
support 2. A magnet 5 made of a cylindrical permanent magnet is fixed to the upper surface (the
Z1 side in FIG. 2) of the rear yoke 3. The magnet 5 is magnetized such that the front side (Z1
side) and the back side (Z2 side) are opposite to each other. For example, as shown in FIG. 2, the
Z1 side is N pole and Z2 side is S pole. It is done. A ring-shaped front yoke 6 is fixed to the
surface of the magnet 5 on the Z1 side. A cylindrical opposing yoke 7 is integrally formed on the
front yoke 6 so as to extend toward the Z1 side.
The rear yoke 3, the inner yoke 4, the front yoke 6 and the opposing yoke 7 are all formed of a
magnetic material such as iron or ferrite. Further, a protrusion 4 a protruding toward the
opposing yoke 7 is integrally formed on the outer peripheral surface of the distal end of the inner
yoke 4, and the inner peripheral surface of the distal end of the opposing yoke 7 is directed to
the inner yoke 4. The protruding projections 7a are integrally formed, and the projections 4a and
the projections 7a face each other. At this time, a gap G with a minute interval is formed between
the protrusion 4 a and the protrusion 7 a. Therefore, in the present embodiment, a magnetic
circuit for detection is formed by the rear yoke 3, the inner yoke 4, the magnet 5, the front yoke
6 and the opposing yoke 7. A reflecting member 20 formed in a ring shape is provided on the
front surface of the support 2 outside the outer peripheral surface of the opposing yoke 7. At the
inner peripheral edge portion of the reflecting member 20, parts of the inner yoke 4 and the
opposing yoke 7 project. The reflecting member 20 is formed of synthetic resin or the like, and
its front surface is a reflecting surface 20 a. As shown in FIG. 3, the reflecting surface 20a has a
tapered surface 20a1 which is inclined in the Z2 direction from the outer peripheral side to the
inner peripheral side. That is, in the tapered surface 20a1, the surface on the outer peripheral
side of the reflecting member 20 protrudes more forward than the surface on the inner
peripheral side. Further, the reflecting surface 20a of the present embodiment is formed so as to
be short on the flat surface 20a2 formed short vertically to the Z axis outside the tapered surface
20a1 and perpendicular to the Z axis on the inside of the tapered surface 20a1. The flat surface
20a3 and the tapered surface 20a1 have inclined surfaces 20a4 that are inclined and formed
short on the opposite side, and the surfaces 20a1, 20a2, 20a3, and 20a4 are continuously
formed. An inclined surface 7b is formed in the facing yoke 7 so as to be continuous with the
inclined surface 20a4. As shown in FIG. 2, a vibrating member 10 is provided in front of the
support 2. The vibrating member 10 is formed of a diaphragm made of paper, a laminate of
paper and resin film, or paper impregnated with resin, and is supported by the cover member 11.
The cover member 11 is formed of a synthetic resin in a disc shape, and is supported so as to be
located in front of the support 2. Therefore, an introduction path 13 having a gap of a
predetermined width is formed between the vibrating member 10 and the reflecting member 20.
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Although the cover member 11 is fixed to the inner yoke 4 or the opposing yoke 7, the cover
member 11 may be fixed to another portion such as the reflecting surface 20a. The cover
member 11 is formed to have a diameter smaller than the diameter R of the support 2 as
illustrated, and a part of the reflection member 20 is formed from the outer peripheral edge of
the cover member 11. It protrudes outside. The outer peripheral portion of the cover member 11
is set to overlap with a part of the inner periphery of the reflecting surface 20a. The cover
member 11 in the present embodiment has a concave shape in which the back surface side (Z2
side) is open. The outer peripheral edge of the vibrating member 10 is fixed to the inner
peripheral edge of the cover member 11 with an adhesive or the like. At this time, the cross
section of the vibrating member 10 is substantially W-shaped. As shown in FIG. 3, a cylindrical
bobbin 12 is fixed on the Z2 side of the vibrating member 10, and a detection coil C is wound
around the outer peripheral surface of the bobbin 12. At this time, the bobbin 12 around which
the detection coil C is wound is located between the gap G formed between the protrusion 4 a
and the protrusion 7 a. The vibrating member 10 has a curved ring-shaped vibrating portion 10
a outside the bobbin 12 and a curved circular vibrating portion 10 b inside the bobbin 12. On the
front surface of the cover member 11, a plurality of circular small holes 11a are formed at equal
intervals along the circumferential direction. Therefore, when the cover member 11 is viewed
from the front on the Z1 side, a part of the vibrating portion 10a is exposed from the small hole
11a, and the vibrating portion 10b is not exposed. Next, the operation of the directional
microphone 1 will be described with reference to FIG. When a sound wave is incident from the
S1 direction (Z1 side) which is the front of the directional microphone 1, the sound wave passes
through the small hole 11a of the cover member 11 and strikes the vibrating portion 10a of the
vibrating member 10, and the vibrating portion 10a is directly vibrated. . When the vibrating
portion 10a vibrates, the detection coil C crosses in the Z direction with respect to the magnetic
field directed from the protrusion 7a to the protrusion 4a, so that a detection current is induced
in the detection coil C. The detected current is amplified by a predetermined amplifier circuit or
the like and output as a sound signal to a speaker or a recording device. When sound waves are
generated from the front, the sound waves incident on the flat surface 20a2 of the reflection
member 20 are reflected in the Z1 direction, and most of the sound waves incident on the taper
surface 20a1 of the reflection member 20 remain as they are. It is reflected toward the Z1 side.
In the directional microphone 1, when a sound wave is incident from the direction S 2
perpendicular to the Z direction, the sound wave is the outer surface 2 b of the support 2, the
outer surface 20 b of the reflection member 20 and the outer surface 11 c of the cover member
11. It is hit and reflected. Therefore, since the vibrating parts 10a and 10b do not vibrate, the
sensitivity to the sound wave from the S2 direction can be sufficiently lowered. Further, since the
flat surface 20a2 of the reflection surface 20a and the back surface 11b of the cover member 11
have the same position in the Z direction, the sound wave from the S2 direction does not intrude
into the introduction path 13 and vibration occurs. The member 10 is not vibrated. Further,
when a sound wave is incident from the S3 direction inclined with respect to the S1 direction (or
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the S2 direction), a direct sound wave S3a directly incident on the vibrating portion 10a through
the small hole 11a and a reflection surface of the reflection member 20 A reflected sound wave
S3b incident on 20a is generated. At this time, the reflected sound wave S3b is reflected by the
reflection surface 20a and then guided through the introduction path 13 so as to be incident
from the back surface side of the vibrating portion 10a of the vibrating member 10. Then, the
vibration due to the sound pressure of the reflected sound wave S3b acts in the direction to
cancel the vibration due to the sound pressure of the direct sound wave S3a. That is, since the
direct sound waves S3a and the reflected sound waves S3b are waves of the same waveform
emitted from the same sound source and the phases are opposite to each other, they cancel each
other's sound waves. Thus, the bobbin 12 around which the detection coil C is wound does not
vibrate in the Z direction, and thus no detection current is induced in the detection coil C.
Alternatively, since the vibration is weakened by suppressing each other's sound waves, the
induced detection current can be reduced. Therefore, the sensitivity can be lowered for the sound
wave incident from the S3 direction. Further, when the sound wave is incident from the S4
direction which is closer to the S2 side than the S3 direction, the direct sound wave S4a is
directly incident on the vibrating portion 10a through the small hole 11a. Also, the reflected
sound wave S4b is reflected by the reflection surface 20a through the introduction path 13 and
is incident from the back side of the vibrating part 10a. At this time, the reflection sound wave
S4b is reflected to the flat surface 20a3 of the reflection surface 20a It is reflected by the
inclined surface 7b of the yoke 7 and reaches the back side of the vibrating portion 10a. Also in
this case, since the sound waves of the same waveform having different phases are applied to the
vibrating portion 10a of the vibrating member 10 from the front side and the back side, the
direct sound waves S4a and the reflected sound waves S4b cancel each other, and the vibrating
member is vibrated. 10 will not vibrate.
Alternatively, the sound waves of each other are suppressed and the vibration of the vibrating
member 10 is weakened. Therefore, since a detection current is not induced in the detection coil
C, no sound signal is output. Alternatively, since the induced detection current is reduced, the
output of the sound signal can be reduced. Thus, the sensitivity can also be lowered for sound
waves incident from the S4 direction. As shown in FIG. 3, in the reflection member 20, when
inclined surfaces 20a4 and 7b having an inclination opposite to the tapered surface 20a1 are
formed on the inner peripheral side, vibration is reflected by the tapered surface 20a1 and
vibration occurs. It becomes possible to reflect again the sound wave which did not reach the
member 10 and to be directed to the vibrating member 10. As described above, in the present
embodiment, the sound incident from a direction other than the front can reduce the sensitivity
of the sound collection unit 2A, so that high directivity can be exhibited. In addition, since both
the length dimension in the Z direction and the diameter dimension in the XY plane can be made
short, it is possible to obtain a small microphone that can exhibit high directivity. Further, in the
present embodiment, although the case where the reflective surface 20a is tapered facing inward
has been described, the present invention is not limited thereto. For example, the reflective
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surface 20a is formed in an XY plane perpendicular to the Z direction. It may be a reflective
surface. Alternatively, it may be a reflecting surface formed by a curved surface such as a
paraboloid or a curved surface, or it may be a reflecting surface combining a curved surface and
a flat surface. According to the present invention described above, the sensitivity can be lowered
particularly to sounds other than those incident from the front, so that high directivity can be
exhibited, and the size of the apparatus can be reduced. It can also be illustrated. BRIEF
DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view showing a directional microphone
according to the present invention, FIG. 2 is a cross-sectional view taken along line 2-2 in FIG. 1,
FIG. 3 is a diagram showing a mechanism for exhibiting directivity Partially enlarged sectional
view of 2 [Description of the code] C detection coil 1 directional microphone 2 support 2a
recessed portion 2A sound collecting portion 3 lower yoke 4 internal yoke 4a, 7a protrusion 5
magnet 6 upper yoke 7 opposed yoke 7b inclined Surface 10 vibration member 10a, 10b
vibration portion 11 cover member 11a small hole 12 bobbin 20 reflection member 20a
reflection surface 20a1 tapered surface 20a2, 20a3 flat surface 20a4 inclined surface
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