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JP2013055466

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DESCRIPTION JP2013055466
Abstract: A dynamic microphone unit and a dynamic microphone capable of reducing an impact
sound generated when a diaphragm is largely displaced. SOLUTION: A diaphragm 5 which
receives and vibrates a sound wave, a voice coil 6 fixed to the diaphragm 5 and vibrated together
with the diaphragm 5, and a magnetic gap in which the voice coil 6 is disposed A magnetic
circuit to be generated, a rear air chamber 15 formed on the back side of the diaphragm 5, and a
second air chamber 9 formed behind the voice coil 6 and in communication with the rear air
chamber 15 In the second air chamber 9, a thin plate-like acoustic resistor 50 having an elastic
force limits the volume of the second air chamber 9 and is tensioned at a position where the
voice coil 6 can contact within its maximum displacement. Is assigned and placed. [Selected
figure] Figure 1
ダイナミックマイクロホンユニットおよびダイナミックマイクロホン
[0001]
The present invention relates to a dynamic microphone unit and a dynamic microphone, and in
particular, aims to reduce an impact sound generated when a diaphragm is largely displaced due
to the application of an excessive sound pressure.
[0002]
The nondirectional component of the dynamic microphone is resistance control.
13-05-2019
1
Therefore, the frequency response can be flattened by arranging the acoustic resistance
immediately after the diaphragm.
[0003]
7 and 8 show an example of a conventional dynamic microphone unit. In FIGS. 7 and 8, reference
numeral 1 denotes a unit case which forms a base of the microphone unit. The unit case 1 has a
cylindrical shape with a bottomed outer shape, and an inner cylinder 11 extending downward
from the upper end is formed integrally with the inner side and extends radially inward to the
lower end of the inner cylinder 11. A circular ridge 12 is formed.
[0004]
In the inner cylinder 11 of the unit case 1, a magnetic circuit is configured by accommodating
the following magnetic circuit forming members. First, a petri dish-like yoke 2 is fitted in the
inner cylinder 11 and supported by the collar portion 12 of the inner cylinder 11, and the outer
peripheral surface of the peripheral wall of the yoke 2 is in contact with the inner peripheral
surface of the inner cylinder 11. There is. A disk-shaped magnet 3 having an outer diameter
smaller than the inner diameter of the peripheral wall of the yoke 2 is fixed on the bottom plate
of the yoke 2, and a disk-shaped pole piece 4 is fixed on the magnet 3. A ring yoke 21 is fixed to
the upper end surface of the peripheral wall of the yoke 2. The pole piece 4 and the ring yoke 21
have substantially the same thickness and are fixed at substantially the same height position, and
the outer peripheral surface of the pole piece 4 and the inner peripheral surface of the ring yoke
21 face each other at an appropriate distance, A magnetic gap is formed. The magnetic circuit
component is substantially accommodated in the inner cylinder 11, and the upper end surface of
the pole piece 4 and the upper end surface of the inner cylinder 11 are at substantially the same
height position.
[0005]
The magnetic flux emanating from the magnet 3 returns to the magnet 3 through a magnetic
circuit composed of the yoke 2, the ring yoke 21, the magnetic gap and the pole piece 4. Thus,
the magnetic flux traverses the magnetic gap. The outer diameter of the magnet 3 is smaller than
the outer diameter of the pole piece 4, and an air chamber 9 is formed between the outer
peripheral surface of the magnet 3 and the inner peripheral surface of the inner cylinder 11
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below the magnetic gap. The outer diameter of the magnet 3 is smaller than the outer diameter
of the pole piece 4, and an air chamber 9 wider than the magnetic gap is formed on the outer
peripheral side of the magnet 3 below the magnetic gap. A plurality of holes 22 are formed in the
yoke 2 vertically through a portion corresponding to the bottom thereof, and the holes 22
connect a space surrounded by the air chamber 9 and the circular flange 12 of the unit case 1. It
is.
[0006]
A projecting edge 14 is formed on the upper end of the unit case 1 along the outer periphery of
the unit case 1, and an upper end portion of the unit case 1 is inward of the projecting edge 14
and more than the projecting edge 14. At a low position, the projections 13 are formed along a
circle concentric with the flanges 14. The outer peripheral edge portion of the diaphragm 5 is
fixed to the upper surface of the projection 13. The diaphragm 5 is made of a thin film of
synthetic resin or metal, and the center dome 51 and the sub dome 52 surrounding the center
dome 51 are provided by molding the material. While the center dome 51 has a shape in which a
part of the spherical surface is cut away, the sub dome 52 is formed in a partial arc shape in
cross section and continuously formed on the outer peripheral edge of the center dome 51. It is
fixed on the top of the Since the outer peripheral edge of sub dome 52 is fixed as described
above, diaphragm 5 vibrates in the front-rear direction (up and down direction in FIG. 7) with the
outer peripheral edge of sub dome 52 as a fulcrum can do.
[0007]
The voice coil 6 is fixed to the diaphragm 5 along the circular boundary between the center
dome 51 and the sub dome 52. The voice coil 6 is formed and hardened in a cylindrical shape by
winding a thin conductive wire, and one end of the cylindrical shape is fixed to the diaphragm 5.
With the outer peripheral edge of the sub dome 52 of the diaphragm 5 fixed as described above,
the voice coil 6 is located in the magnetic gap, and the voice coil 6 is separated from the ring
yoke 21 and the pole piece 4 ing.
[0008]
An equalizer 8 which also serves as a protective member for the diaphragm 5 is disposed on the
front side of the diaphragm 5 by fixing its outer peripheral edge portion to the projecting edge
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portion 14 of the unit case 1. The ceiling surface of the central portion of the equalizer 8 is
formed in a dome shape, and a gap with a constant distance is maintained between the
diaphragm 5 and the center dome 51. The equalizer 8 has a plurality of holes 82 for guiding a
sound wave from the outside to the diaphragm 5.
[0009]
The lower end of the unit case 1 is closed, and a relatively large air chamber 15 is formed inside
the unit case 1. An acoustic resistor 16 is disposed in close contact with the lower surface of the
yoke 2. The inner peripheral surface of the flange portion 12 of the unit case 1 is a cylindrical
surface, and the outer peripheral surface of the acoustic resistor 16 is supported by the inner
peripheral surface of the flange portion 12. The acoustic resistor 12 is formed by thickly
laminating a non-woven fabric or the like. The acoustic resistor 16 is disposed on the back side of
the diaphragm 5, and the space on the back side of the diaphragm 5 communicates with the
acoustic resistor 16 through the magnetic gap, the air chamber 9, and the hole 22 of the yoke 2,
and further the air chamber. It leads to 15.
[0010]
When the diaphragm 5 receives a sound wave, it vibrates back and forth according to the change
of the sound pressure, and the voice coil 6 also vibrates back and forth together with the
diaphragm 5. When the voice coil 6 vibrates, the voice coil 6 crosses the magnetic flux passing
through the magnetic gap, and the voice coil 6 generates a voice signal corresponding to the
change in sound pressure. In this manner, electroacoustic conversion is performed, and for
example, audio signals are output to the outside from both ends of the voice coil 6 routed along
the back surface of the sub dome 52.
[0011]
According to the dynamic microphone unit configured as described above, the space on the back
side of the diaphragm 5 is divided by the voice coil 6 into the space on the back side of the
center dome 51 and the space on the back side of the sub dome 52 The voice coil 6 is in
communication via the inner circumferential magnetic gap and the outer circumferential
magnetic gap. Since it is effective to narrow the magnetic gap in order to increase the sensitivity
of the dynamic microphone unit, the magnetic gap is narrowed as much as possible in a range
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where the voice coil 6 does not contact the pole piece 4 and the ring yoke 21. There is.
Therefore, the space on the back side of the diaphragm 5 is substantially the same as the space
on the back side of the center dome 51 and the space on the back side of the sub dome 52 by the
voice coil 6 as described above.
[0012]
Now, the acoustic capacity of the back side space of the center dome 51 is Sc, the acoustic
capacity of the back side space of the sub dome 52 is Ss, and the gap generated between the
inner peripheral surface of the voice coil 6 and the outer peripheral surface of the pole piece 4
The acoustic mass is mgi, the acoustic resistance is rgi, the acoustic mass by the gap generated
between the outer circumferential surface of the voice coil 6 and the inner circumferential
surface of the ring yoke 21 is mgo, and the acoustic resistance is rgo. The sound pressure applied
to the diaphragm 5 from the front side is P1, the acoustic resistance of the acoustic resistor 16
disposed in the air chamber 11 of the unit case 1 is r1, the acoustic mass of the front air
chamber of the diaphragm 5 is mo, the acoustic capacity is So. Further, assuming that the
acoustic capacity of the air chamber 9 generated between the inner peripheral surface of the
peripheral wall of the yoke 2 and the outer peripheral surface of the magnet 3 is Sg, the acoustic
capacities Sc and Ss of the two spaces are shown in FIG. As described above, the acoustic mass
mgi, the acoustic resistance rgi, the acoustic capacity Sg, the acoustic mass mgo, and the acoustic
resistance rgo are connected.
[0013]
FIG. 9 is an equivalent circuit of the microphone unit shown in FIG. 7 and FIG. 8 including the
acoustic mass, the acoustic capacity, and the acoustic resistance described above. As shown in
FIG. 9, a sound pressure P1, an acoustic mass mo, an acoustic capacity So, an acoustic mass mgi,
an acoustic resistance rgi, an acoustic resistance rgo, an acoustic mass mgo, and an acoustic
capacity Ss are connected in series. The connection point of the acoustic capacity So and the
acoustic mass mgi, and the connection point of the sound pressure P1 and the acoustic capacity
Ss are connected by an acoustic capacity Sc, and the connection point of the acoustic resistance
rgi and the acoustic resistance rgo, the sound pressure P1 and The connection point of the
acoustic capacity Ss is connected with the acoustic resistance r1 and the acoustic capacity S1
connected in series. Further, the acoustic capacitance Sg is connected in parallel to the series
connection of the acoustic resistance r1 and the acoustic capacitance S1.
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[0014]
As apparent from FIG. 9, the inner peripheral acoustic mass mgi of the magnetic gap divided by
the voice coil 6 and the acoustic capacitance Sg of the air chamber 9 constitute a resonant
circuit, and the outer acoustic mass of the magnetic gap The mgo and the acoustic capacitance Ss
in the back side space of the sub dome 52 constitute a resonant circuit. The volume of the air
chamber 9 is smaller than the volume of the air chamber 11 occupying the lower half of the unit
case 1, and the acoustic capacity Sg is likely to resonate in cooperation with the acoustic mass
mgi. There is. When this resonance occurs, a peak occurs at a specific frequency and the
frequency characteristic is degraded.
[0015]
In order to reduce the above-mentioned resonance, it is conceivable to make the volume of the
air chamber 9 further smaller to minimize the acoustic capacity Sg to a negligible extent, thereby
making it difficult to resonate with the acoustic mass mgi. The conventional example shown in
FIG. 10 is an example thereof. In this example, the acoustic resistor 25 is disposed in the air
chamber 9 generated between the inner circumferential surface of the peripheral wall of the
yoke 2 and the outer circumferential surface of the magnet 3, and the acoustic resistor 25 is in
contact with the bottom surface of the yoke 2. The air chamber 9 is formed on the upper surface
side of the acoustic resistor 25. Therefore, the volume of the air chamber 9 is limited by the
acoustic resistor 25, and the acoustic capacity Sg of the air chamber 9 is extremely small.
Assuming that the acoustic resistance of the acoustic resistor 25 is r1, the acoustic capacitance
Sg is connected to the acoustic capacitance S1 via the acoustic resistance r1 and the hole 22 of
the yoke 2. The equivalent circuit is shown in FIG. In the equivalent circuit shown in FIG. 11, as
described with reference to FIG. 10, the acoustic capacity Sg is limited to an extremely small
capacity that can be ignored due to the presence of the acoustic resistor 25, so the acoustic
capacity Sg is not shown. It is done. Thus, in the example shown in FIG. 10, resonance due to the
air chamber 9 is less likely to occur, and good frequency characteristics without peaks can be
obtained in the audio frequency band.
[0016]
As described above, in order to arrange the acoustic resistor 25 in the air chamber 9 behind the
voice coil 6 to make the volume of the air chamber 9 extremely small, it is necessary to make the
acoustic resistor 25 approach the voice coil 6. When the acoustic resistor 25 has a felt-like
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structure, a non-woven fabric or a structure similar to a non-woven fabric, as shown by reference
numeral 251 in FIG. 10, a part of fibers constituting the acoustic resistor 25 rise. When the
diaphragm 5 vibrates to a large extent, the voice coil 6 comes in contact with the rise 25 of the
above-mentioned fibers to generate abnormal noise, and the vibration of the voice coil 6 faithful
to the sound wave is inhibited, and faithful electroacoustic conversion can not be performed. .
Therefore, there is a limit in bringing the acoustic resistor 25 closer to the voice coil 6, and a
limitation in reducing the volume of the air chamber 9 to reduce the acoustic capacity Sg.
Therefore, the resonance caused by the air chamber 9 is limited. There is also a limit to
prevention.
[0017]
By the way, there is a dynamic microphone which is attached to an instrument and used to pick
up the sound of the instrument. In particular, in a dynamic microphone such as a bass drum that
picks up the sound of a musical instrument that generates a sound wave with a large sound
pressure at a low frequency, the diaphragm is greatly displaced. It may be broken by being
caught between Therefore, in the dynamic microphone in which the lead wire of the voice coil is
wired along the inner surface of the sub-dome of the diaphragm facing the ring yoke, the present
inventors have found that the maximum displacement position when the diaphragm swings
toward the pole piece. The present invention has previously proposed an invention characterized
in that an amplitude restricting means for restricting the lead wire to a position where it does not
abut on the ring yoke is provided on the magnetic generation circuit side (see Patent Document
1).
[0018]
Also, the present inventor applies an elastic layer on the inner surface side of the sub dome of
the diaphragm adjacent to the voice coil so that the lead wire of the voice coil is not broken even
if the diaphragm is pressed against the magnetic generation circuit, The invention relating to a
dynamic microphone characterized in that the above-mentioned lead wire is elastically held on
the side of the sub dome through a layer has been proposed previously (see Patent Document 2).
[0019]
JP, 2005-260306, A JP, 2006-019791, A
[0020]
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According to the inventions described in Patent Document 1 and Patent Document 2, when a
large sound pressure is applied and the diaphragm is largely displaced, the diaphragm strikes the
magnetic generation circuit which is the fixed portion, and the movement of the diaphragm is
stopped. ing.
With this configuration, an effect of preventing disconnection of the lead wire of the voice coil
can be obtained.
However, there is a disadvantage that noise is generated when the diaphragm strikes the fixed
part.
[0021]
The present invention solves the problems of the above-described conventional dynamic
microphone unit, that is, a dynamic microphone unit capable of reducing an impact sound
generated when the diaphragm is largely displaced, and a dynamic microphone using the
microphone unit. Intended to be provided.
[0022]
The present invention includes a diaphragm that receives and vibrates sound waves, a voice coil
that is fixed to the diaphragm and that vibrates with the diaphragm, and a magnetic gap in which
the voice coil is disposed to generate a magnetic field in the magnetic gap. A dynamic circuit
comprising a magnetic circuit, a rear air chamber formed on the back side of the diaphragm, and
a second air chamber formed behind the voice coil and in communication with the rear air
chamber. A microphone unit, wherein a thin-plate acoustic resistor having an elastic force can
limit the volume of the second air chamber and the voice coil can be in contact with the second
air chamber within its maximum displacement. The most important feature is that the position is
placed with tension.
[0023]
The second air chamber at the rear of the voice coil is limited in volume by a thin plate-like
acoustic resistor, and resonance between the acoustic mass of the magnetic gap portion and the
acoustic capacity of the second air chamber is unlikely to occur. You can get it.
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The thin plate-like acoustic resistor is disposed with tension, and when the voice coil is largely
displaced and comes in contact with the acoustic resistor, the acoustic resistor bends to cause
impact due to the contact of the voice coil. The power can be mitigated and the generation of
noise can be suppressed.
[0024]
It is a longitudinal cross-sectional view which shows the principal part of the Example of the
dynamic microphone unit which concerns on this invention.
It is a longitudinal cross-sectional view which shows the state which the voice coil displaced large
in the said Example, and was in contact with the acoustic resistor according to FIG. It is a top
view which shows the acoustic resistance holding body in the said Example. It is a longitudinal
cross-sectional view of the said acoustic resistance holding body. It is a longitudinal crosssectional view which shows a part of fixing process of the said acoustic resistance holding body
and an acoustic resistor. It is a longitudinal cross-sectional view which shows the final form of
the acoustic resistance holding body and the acoustic resistor which passed through the said
adhering process. It is a longitudinal cross-sectional view which shows an example of the
conventional dynamic microphone unit. It is a longitudinal cross-sectional view which expands
and shows the state which the voice coil displaced large in the said prior art example, and which
expanded. It is an equivalent circuit schematic of the conventional dynamic microphone unit. FIG.
18 is a longitudinal cross-sectional view showing another example of the conventional dynamic
microphone unit with the main parts enlarged. It is an equivalent circuit schematic of the
conventional dynamic microphone unit shown in FIG.
[0025]
Hereinafter, an embodiment of a dynamic microphone unit according to the present invention
will be described with reference to the drawings, and the dynamic microphone according to the
present invention will also be referred to. The same components as those of the conventional
dynamic microphone unit shown in FIGS. 7, 8 and 10 are denoted by the same reference
numerals.
[0026]
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In FIGS. 1 and 2, reference numeral 1 denotes a unit case which forms a base of the microphone
unit. Similar to the unit case 1 of the prior art, the unit case 1 has a cylindrical shape with a
bottomed outer shape, and an inner cylinder 11 extending downward from the upper end is
integrally formed inside by an integral molding. A radially inward extending collar portion 12 is
formed at the lower end portion 11 along the entire circumference of the inner cylinder 11.
[0027]
In the inner cylinder 11 of the unit case 1, a magnetic circuit is configured by accommodating
the following magnetic circuit forming members. First, a petri dish-like yoke 2 is fitted in the
inner cylinder 11, and the yoke 2 is supported by the collar 12 of the inner cylinder 11. The
outer peripheral surface of the peripheral wall of the yoke 2 is the inner peripheral surface of the
inner cylinder 11. I am in contact with A disc-shaped magnet 3 having an outer diameter smaller
than the inner diameter of the peripheral wall of the yoke 2 is fixed on the bottom plate of the
yoke 2 by adhesion, and a disc-shaped pole piece 4 is fixed on the magnet 3 by adhesion It is
done. A ring yoke 21 is fixed to the upper end surface of the peripheral wall of the yoke 2 by
adhesion. The pole piece 4 and the ring yoke 21 have substantially the same thickness and are
fixed at substantially the same height position, and the outer peripheral surface of the pole piece
4 and the inner peripheral surface of the ring yoke 21 face each other at an appropriate distance.
A space forms a circular magnetic gap. The magnetic circuit component is accommodated in the
inner cylinder 11, and the upper end surface of the pole piece 4 and the upper end surface of the
inner cylinder 11 are at substantially the same height position.
[0028]
The magnetic flux emanating from the magnet 3 returns to the magnet 3 through a magnetic
circuit composed of the yoke 2, the ring yoke 21, the magnetic gap and the pole piece 4. Thus,
the magnetic flux traverses the magnetic gap. The outer diameter of the magnet 3 is smaller than
the outer diameter of the pole piece 4, and an air chamber 9 is formed between the outer
peripheral surface of the magnet 3 and the inner peripheral surface of the inner cylinder 11
below the magnetic gap. The outer diameter of the magnet 3 is smaller than the outer diameter
of the pole piece 4, and an air chamber 9 wider than the magnetic gap is formed on the outer
peripheral side of the magnet 3 below the magnetic gap. A portion corresponding to the bottom
of the yoke 2 is vertically penetrated to form a plurality of holes 22. The holes 22 are a space
surrounded by the air chamber 9 and the circular flange 12 of the unit case 1, and further Is
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connected to a relatively large air chamber 15 inside the unit case 1. The air chamber 15 is a
main air chamber formed on the back side of the diaphragm 5 and is referred to as a rear air
chamber. On the other hand, the air chamber 9 at the rear of the magnetic gap is a small air
chamber, hereinafter referred to as a second air chamber.
[0029]
A projecting edge 14 is formed on the upper end of the unit case 1 along the outer periphery of
the unit case 1, and an upper end portion of the unit case 1 is inward of the projecting edge 14
and more than the projecting edge 14. At a low position, the projections 13 are formed along a
circle concentric with the flanges 14. The outer peripheral edge portion of the diaphragm 5 is
fixed to the upper surface of the projection 13. The diaphragm 5 is made of a thin film of
synthetic resin or metal, and the center dome 51 and the sub dome 52 surrounding the center
dome 51 are provided by molding the material. While the center dome 51 has a shape in which a
part of the spherical surface is cut away, the sub dome 52 is formed in a partial arc shape in
cross section and continuously formed on the outer peripheral edge of the center dome 51. It is
fixed on the top of the Since the outer peripheral edge of sub dome 52 is fixed as described
above, diaphragm 5 vibrates in the front-rear direction (up and down direction in FIG. 7) with the
outer peripheral edge of sub dome 52 as a fulcrum can do.
[0030]
The voice coil 6 is fixed to the diaphragm 5 along the circular boundary between the center
dome 51 and the sub dome 52. The voice coil 6 is formed and hardened in a cylindrical shape by
winding a thin conductive wire, and one end of the cylindrical shape is fixed to the diaphragm 5.
With the outer peripheral edge of the sub dome 52 of the diaphragm 5 fixed as described above,
the voice coil 6 is located in the magnetic gap, and the voice coil 6 is separated from the ring
yoke 21 and the pole piece 4 ing.
[0031]
An equalizer 8 which also serves as a protective member for the diaphragm 5 is disposed on the
front side of the diaphragm 5 by fixing its outer peripheral edge portion to the projecting edge
portion 14 of the unit case 1. The ceiling surface of the central portion of the equalizer 8 is
formed in a dome shape, and a gap with a constant distance is maintained between the
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diaphragm 5 and the center dome 51. The equalizer 8 has a plurality of holes 82 for guiding a
sound wave from the outside to the diaphragm 5.
[0032]
When the diaphragm 5 receives a sound wave, the diaphragm 5 vibrates back and forth
according to the change of the sound pressure, and along with the vibration of the diaphragm 5,
the voice coil 6 also vibrates back and forth. The voice coil 6 crosses the magnetic flux passing
through the magnetic gap by oscillating back and forth, and generates an audio signal
corresponding to a change in sound pressure. In this manner, electroacoustic conversion is
performed, and for example, audio signals are output to the outside from both ends of the voice
coil 6 routed along the back surface of the sub dome 52.
[0033]
A major feature of this embodiment is that a thin plate-like acoustic resistor 50 having an elastic
force limits the volume of the second air chamber 9 and the voice coil 6 contacts the second air
chamber 9 within its maximum displacement. It is to be placed by applying tension to a position
where it can. The second air chamber 9 is formed in a circular shape concentric with the
cylindrical voice coil 6 between the outer peripheral surface of the magnet 3 and the inner
peripheral surface of the peripheral wall of the yoke 2. A ring-shaped acoustic resistance holder
40 is disposed.
[0034]
The structure of the said acoustic resistance holding body 40 is shown in FIG. 3, FIG. In FIG. 3
and FIG. 4, grooves 42 having a predetermined width are formed along the concentric circles on
the upper and lower surfaces of the ring-shaped acoustic resistance holding body 40, and both
sides of the grooves 42, that is, Circular flat surfaces 43 and 44 are formed on the
circumferential side and the outer circumferential side. The acoustic resistance holding body 40
is formed in a symmetrical shape so that it may be turned upside down. In the groove 42, a
plurality of holes 41 penetrating the acoustic resistance holding body 40 in the vertical direction
(thickness direction) are formed at equal intervals in the circumferential direction. An acoustic
resistor 50 is fixed to one side in the vertical direction of the acoustic resistance holder 40, the
upper surface in the illustrated example, and the acoustic resistor 50 covers the groove 42 from
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the upper side. Therefore, the acoustic resistor 50 also covers the hole 41 from the upper side.
[0035]
5 and 6 show an example of a method of fixing the acoustic resistor 50 to the acoustic resistance
holder 40. FIG. Although FIG. 5 shows a state in which the acoustic resistor 50 is fixed to the
upper surface of the acoustic resistance holding body 40, the following steps are performed
before the state of FIG. 5 is reached. First, the peripheral portion of the thin plate material of the
acoustic resistor 50 is adhered with an adhesive tape or the like in a state where an appropriate
tension is applied to a flat surface plate. The material of the acoustic resistor 50 is a material that
can be bent when an external force is applied in a state in which a suitable tension is applied, and
a material having a suitable acoustic resistance. One such material is, for example, nylon mesh.
Next, an adhesive is applied to the inner peripheral surface flat surface 43 and the outer
peripheral surface flat surface 44 on one side of the acoustic resistance holding body 40, and the
material of the acoustic resistor 50 in a tensioned state as described above. The adhesive coated
surface of the acoustic resistance holder 40 is pressed, and the adhesive is cured while
maintaining this state.
[0036]
FIG. 5 shows a state in which the acoustic resistance holding body 40 is turned upside down after
the adhesive is cured and the materials of the acoustic resistance holding body 40 and the
acoustic resistance body 50 are fixed. Next, as shown by the arrows in FIG. 5, the material of the
acoustic resistor 50 is cut off along the inner and outer circumferences of the acoustic resistor
holder 40. Thus, as shown in FIG. 6, an assembly of the acoustic resistance holding body 40 and
the acoustic resistance body 50 is completed.
[0037]
The solid body of the acoustic resistance holding body 40 and the acoustic resistance body 50 is
dropped into the second air chamber 9 as shown in FIGS. 1 and 2, and the bottom surface of the
acoustic resistance holding body 40 is a bottom surface inside the yoke 2. It abuts and is fixed. In
such an assembly mode, the acoustic resistance holding body 40 holds the acoustic resistance
body 50 on the side facing the voice coil 6, and the second air chamber 9 is formed by the
acoustic resistance holding body 40 and the acoustic resistance body 50. Is limited to a very
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small volume on the side facing the voice coil 6. Further, the lower end of the voice coil 6 faces
the groove 42 of the acoustic resistance holder 40, and the acoustic resistor 50 covering the
groove 42 from the upper surface side can contact the voice coil 6 within its maximum
displacement. It is placed in position. In other words, when the voice coil 6 is largely displaced
toward the acoustic resistor 50, as shown in FIG. 2, the lower end of the voice coil 6 contacts the
acoustic resistor 50 and the acoustic resistor 50 is bent downward. It is not supposed to be.
[0038]
Since the acoustic resistor 50 has elastic force and is given an appropriate tension and held
above the groove 42 of the acoustic resistance holder 40, when the lower end of the voice coil 6
is separated from the acoustic resistor 50, As shown in FIG. 1, it returns to flat form. Therefore,
when the lower end of the voice coil 6 contacts, the acoustic resistor 50 acts like a damper that
absorbs the contact energy of the voice coil 6 and absorbs the impact force due to the contact of
the voice coil 6, Eliminate the impact noise or reduce the impact noise.
[0039]
The acoustic resistance holding body 40 does not have a structure in which the acoustic resistor
50 is directly fixed to the hole 41 communicating the rear air chamber 15 with the second air
chamber 9, and the diameter above the hole 41 is larger than the diameter of the hole 41. A wide
groove 42 is formed over the entire circumference, and the acoustic resistor 50 is fixed so as to
cover the groove 42 from above. Therefore, the area in which the acoustic resistor 50 can be
bent by the contact of the voice coil 6 is larger than the area of the groove having a width
corresponding to the diameter of the hole 41, and the voice coil 6 It is possible to enhance the
impact noise reduction effect when in contact.
[0040]
As described for the conventional dynamic microphone, both end wires of the voice coil are fixed
along the back surface of the sub dome 52 of the diaphragm 5 so as to output a signal to the
outside. Therefore, when the diaphragm 5 is largely displaced, the end line of the voice coil 6
may hit the corner of the member constituting the magnetic circuit, for example, the ring yoke
21, and the end line may be cut. However, according to the present embodiment, the downward
displacement of the voice coil 6 and the diaphragm 5 to which the voice coil 6 is fixed in FIGS. 1
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and 2 is restricted by the acoustic resistor 50 as described above. There is also an advantage that
the contact between the member constituting the magnetic circuit and the end line of the voice
coil 6 can be avoided, and the cutting of the end line can be prevented.
[0041]
According to the above embodiment, since the second air chamber 9 at the rear of the voice coil
6 is limited in volume by the thin plate-like acoustic resistor 50 and the acoustic resistance
holder 40 holding the same, Resonance between the acoustic mass and the acoustic capacity of
the second air chamber 9 is unlikely to occur, and good frequency characteristics can be
obtained.
[0042]
The dynamic microphone unit according to the embodiment described above is configured as a
dynamic microphone by assembling the microphone connector for outputting the output signal
of the microphone unit to the outside by assembling this into the microphone case. Be done.
[0043]
Reference Signs List 1 unit case 2 yoke 3 magnet 4 pole piece 5 diaphragm 6 voice coil 8
equalizer 9 second air chamber 15 rear air chamber 21 ring yoke 40 acoustic resistance holder
41 hole 42 groove 50 acoustic resistor
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