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JP2010136131

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Notice
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
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DESCRIPTION JP2010136131
An object of the present invention is to provide a high performance microphone unit which can
be miniaturized. A microphone unit (1) includes a housing (11), a diaphragm (122) disposed
inside the housing (11), and an electric circuit unit (13) that processes an electrical signal
generated based on the vibration of the diaphragm (122). Prepare. The housing 11 includes a
first sound introducing space 113 for guiding the sound outside the housing to the first surface
122 a of the diaphragm 122 via the first sound hole 111, and a housing via the second sound
hole 112. A second sound introducing space 114 for guiding an external sound to a second face
122 b which is a back surface of the first face 122 a of the diaphragm 122 is provided, and the
electric circuit unit 13 is provided in the first sound introducing space 113. Be placed. Further,
the microphone unit 1 is provided with an acoustic resistance unit 15 for adjusting the frequency
characteristic of the first sound introducing space 113. [Selected figure] Figure 2
マイクロホンユニット
[0001]
The present invention relates to a microphone unit that converts an input voice into an electrical
signal, and in particular, it is formed such that sound pressure is applied to both surfaces (front
and back surfaces) of the diaphragm, and the electric signal is converted by vibration of the
diaphragm based on the sound pressure difference. It relates to the configuration of the
microphone unit to be generated.
[0002]
03-05-2019
1
Conventionally, for example, a microphone unit is provided in an information processing system
using an audio communication device such as a cellular phone or a transceiver, or a technology
for analyzing input voice such as a voice authentication system, or a recording device.
It is preferable to pick up only the target voice (user's voice) at the time of a telephone call or the
like, voice recognition and voice recording. For this reason, development of a microphone unit
that accurately extracts a target voice and removes noise (background noise and the like) other
than the target voice has been advanced.
[0003]
As a technique for removing noise and collecting only a target voice in a use environment in
which noise is present, it is possible to give directivity to a microphone unit. As an example of a
microphone unit having directivity, there is conventionally known a microphone unit that is
formed so that sound pressure is applied to both surfaces of a diaphragm (diaphragm) and
generates an electrical signal by vibration of the diaphragm based on the sound pressure
difference ( See, for example, Patent Documents 1 and 2).
[0004]
By the way, in recent years, the miniaturization of electronic devices has progressed, and it has
become important to miniaturize the microphone unit. JP-A-4-217199 JP-A-2005-295278
[0005]
Conventionally, the microphone unit is provided with an electric circuit unit that processes (for
example, amplification processing) an electric signal generated based on the vibration of the
diaphragm. And conventionally, this electric circuit part is arrange | positioned to the exterior of
the sound introduction space which extends from a sound hole to a diaphragm (for example,
refer FIG. 2 of patent document 2).
[0006]
03-05-2019
2
As described above, in recent years, miniaturization of the microphone unit is important. For this
reason, in the microphone unit formed so that sound pressure is applied to both surfaces of the
above-described diaphragm, it has been examined to arrange the electric circuit portion in the
sound conduction space extending from the sound hole to the diaphragm. It was found that good
directivity characteristics could not be obtained in the band. That is, it has been found that the
performance of the microphone unit is degraded even as a configuration in which the electric
circuit unit is disposed in the sound introducing space simply for the purpose of downsizing.
[0007]
Accordingly, an object of the present invention is to provide a high-performance microphone unit
that can be miniaturized.
[0008]
In order to achieve the above object, the present invention comprises a housing, a diaphragm
disposed inside the housing, and an electric circuit unit that processes an electrical signal
generated based on the vibration of the diaphragm. A microphone unit, wherein the housing
includes a first sound introducing space for guiding the sound of the outside of the housing to
the first surface of the diaphragm via the first sound hole, and a second sound hole. A second
sound introducing space for guiding the sound of the outside of the housing to a second face
which is the back face of the first face of the diaphragm, and the electric circuit unit is configured
to An acoustic wave disposed in any one of a space and the second sound introducing space, for
adjusting at least one of a frequency characteristic of the first sound introducing space and a
frequency characteristic of the second sound introducing space It is characterized in that a
resistor portion is provided.
[0009]
According to this configuration, the electric circuit unit that performs signal amplification
processing and the like is arranged in any one of the first sound introducing space and the
second sound introducing space.
For this reason, the microphone unit can be miniaturized as compared with the case where the
electric circuit section is disposed outside the sound introducing space as in the prior art.
03-05-2019
3
[0010]
By the way, when the electric circuit portion is disposed in the sound guide space, the two sound
guides may be caused by the imbalance of the shapes of the two sound guide spaces (the first
sound guide space and the second sound guide space). A difference occurs in the frequency
characteristics of the space.
Specifically, for example, a difference occurs in frequency characteristics in a high frequency
band, and a good noise suppression performance can not be obtained on the high frequency side.
In this respect, the present configuration is configured to adjust the frequency characteristics of
the sound introducing space by providing the acoustic resistance portion, so that good noise
suppression performance can be obtained on the high frequency side. That is, according to this
configuration, the audio signal (electric signal) output from the microphone unit can be made
high in quality with less noise.
[0011]
In the microphone unit of the above configuration, preferably, the acoustic resistance portion is
formed to selectively act on sound in a specific frequency band. The above-mentioned frequency
characteristic difference between the two sound introducing spaces caused by the arrangement
of the electric circuit part in the sound introducing space is hardly recognized in, for example, the
low frequency band but is recognized in the high frequency band. For this reason, as in the
present configuration, by making the acoustic resistance portion selectively act on a specific
frequency band (for example, high frequency band), it is easy to reduce the frequency
characteristic difference between the two sound introducing spaces. .
[0012]
Further, in the microphone unit having the above configuration, the acoustic resistance unit may
be configured by attaching an acoustic resistance member to the housing.
[0013]
As a specific configuration in the case of using the acoustic resistance member, the acoustic
resistance member is at least a part of a path from the first sound hole to the first surface, or the
second sound hole It may be arranged to block at least a part of the path to the second surface.
03-05-2019
4
[0014]
In addition, as another specific configuration in the case of using the acoustic resistance member,
at least a part of a path from the first sound hole to the first surface, and the second sound It may
be arranged to block at least a part of the path from the hole to the second surface.
In this case, the acoustic resistance member may be formed of a first acoustic resistance member
and a second acoustic resistance member separately attached to the housing.
[0015]
In the microphone unit of the above configuration, at least one of the first sound hole and the
second sound hole may be a plurality of through holes and also serve as the acoustic resistance
portion.
[0016]
According to the present invention, the microphone unit can be miniaturized.
And since it becomes the structure which can suppress "deterioration of noise suppression
performance" which may occur when achieving miniaturization, a high quality voice signal is
obtained.
[0017]
Hereinafter, embodiments of a microphone unit to which the present invention is applied will be
described in detail with reference to the drawings.
[0018]
FIG. 1 is a schematic perspective view showing the configuration of the microphone unit of the
present embodiment.
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5
FIG. 2 is a schematic cross-sectional view at a position A-A in FIG.
As shown in FIGS. 1 and 2, the microphone unit 1 of the present embodiment includes a housing
11, a micro electro mechanical system (MEMS) chip 12, an application specific integrated circuit
(ASIC) 13, and a circuit board 14. And an acoustic resistance unit 15.
[0019]
The housing 11 is formed in a substantially rectangular parallelepiped shape, and accommodates
the MEMS chip 12 including the diaphragm (diaphragm) 122, the ASIC 13, and the circuit board
14 therein. The outer shape of the housing 11 is not limited to the shape of this embodiment,
and may be, for example, a cube, or is not limited to a hexahedron such as a rectangular
parallelepiped or a cube, and is other than a polyhedron structure or polyhedron other than
hexahedron (For example, a spherical structure, a hemispherical structure, etc.).
[0020]
As shown in FIGS. 1 and 2, the housing 11 is formed therein with a first sound introducing space
113 and a second sound introducing space 114. The first sound introducing space 113 and the
second sound introducing space 114 are divided by a vibrating film 122 included in the MEMS
chip 12 which will be described in detail later. That is, the first sound introducing space 113 is in
contact with the upper surface (first surface) 122 a side of the vibrating film 122 and the second
sound introducing space 114 is in contact with the lower surface (second surface) 122 b of the
vibrating film 122. It has become.
[0021]
Further, in the upper surface 11 a of the housing 11, a first sound hole 111 and a second sound
hole 112 which are substantially circular in plan view are formed. The first sound hole 111 is
connected to the first sound introducing space 113, whereby the first sound introducing space
113 and the external space of the housing 11 are connected. That is, the sound outside the
housing 11 is guided to the upper surface 122 a of the vibrating membrane 122 by the first
sound introducing space 113 through the first sound hole 111. In the present embodiment,
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6
although the acoustic resistance portion 15 is provided above the first sound hole 111, the sound
wave passes through the acoustic resistance portion 15 and the first sound introducing space
from the external space of the housing 11 It is supposed to get into 113.
[0022]
In addition, the second sound hole 112 is connected to the second sound introducing space 114,
whereby the second sound introducing space 114 and the external space of the housing 11 are
connected. That is, the sound outside the housing 11 is guided to the lower surface 122 b of the
vibrating membrane 122 by the second sound introducing space 114 through the second sound
hole 112. The distance between the first sound hole 111 and the second sound hole 112 is
preferably about 4 to 6 mm for the purpose of improving the S / N (Signal to Noise) ratio of the
sound output from the microphone unit 1.
[0023]
In the present embodiment, the first sound hole 111 and the second sound hole 112 have a
substantially circular shape in plan view, but the present invention is not limited to this. The
shape may be other than a circular shape, for example, a rectangular shape Or the like. Further,
in the present embodiment, one first sound hole 111 and one second sound hole 112 are
provided, but the present invention is not limited to this configuration, and the number of each
may be plural.
[0024]
Further, in the present embodiment, the first sound hole 111 and the second sound hole 112 are
formed on the same surface of the housing 11. However, the present invention is not limited to
this configuration. For example, they may be formed on adjacent surfaces or opposed surfaces.
However, when the two sound holes 111 and 112 are formed in the same surface of the housing
11 as in the present embodiment, the sound path in the voice input device (for example, a mobile
phone etc.) mounting the microphone unit 1 of the present embodiment. Is preferred in that it is
not complicated.
[0025]
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7
FIG. 3 is a schematic cross-sectional view showing the configuration of the MEMS chip 12
provided in the microphone unit 1 of the present embodiment. As shown in FIG. 3, the MEMS
chip 12 has an insulating base substrate 121, a vibrating film 122, an insulating film 123, and a
fixed electrode 124, and forms a capacitor type microphone. The MEMS chip 12 is manufactured
using a semiconductor manufacturing technology.
[0026]
For example, an opening 121a having a substantially circular shape in plan view is formed in the
base substrate 121, whereby sound waves coming from the lower side of the vibrating film 122
reach the vibrating film 122. The vibrating film 122 formed on the base substrate 121 is a thin
film that vibrates (vibrates in the vertical direction) by receiving a sound wave, has conductivity,
and forms one end of an electrode.
[0027]
The fixed electrode 124 is disposed to face the vibrating film 122 with the insulating film 123
interposed therebetween. Thereby, the vibrating membrane 122 and the fixed electrode 124
form a capacitance. A plurality of sound holes 124 a are formed in the fixed electrode 124 so
that sound waves can pass therethrough, and sound waves coming from the upper side of the
vibrating film 122 reach the vibrating film 122.
[0028]
In such a MEMS chip 12, when a sound wave is incident on the MEMS chip 12, the sound
pressure pf is applied to the upper surface 122a of the vibrating film 122, and the sound
pressure pb is applied to the lower surface 122b. As a result, the vibrating membrane 122
vibrates according to the difference between the sound pressure pf and the sound pressure pb,
and the distance Gp between the vibrating membrane 122 and the fixed electrode 124 changes,
and the static charge between the vibrating membrane 122 and the fixed electrode 124 The
capacitance changes. That is, the MEMS chip 12 functioning as a condenser type microphone can
extract the incident sound wave as an electric signal.
03-05-2019
8
[0029]
In the present embodiment, the vibrating membrane 122 is lower than the fixed electrode 124,
but it is configured such that the opposite relationship to this (the vibrating membrane is upper
and the fixed electrode is lower) It does not matter.
[0030]
FIG. 4 is a diagram for explaining the circuit configuration of the ASIC 13 provided in the
microphone unit 1 of the present embodiment.
The ASIC 13 is an embodiment of the electric circuit unit of the present invention, and is an
integrated circuit that amplifies an electric signal generated based on a change in capacitance in
the MEMS chip 12 by the signal amplification circuit 133. In the present embodiment, the charge
pump circuit 131 and the operational amplifier 132 are configured so as to accurately obtain the
change in capacitance in the MEMS chip 12. In addition, a gain adjustment circuit 134 is
included so that the amplification factor (gain) of the signal amplification circuit 133 can be
adjusted. The electrical signal amplified by the ASIC 13 is output to, for example, an audio
processing unit of a mounting substrate (not shown) on which the microphone unit 1 is mounted.
[0031]
Returning to FIG. 2, the circuit board 14 is a board on which the MEMS chip 12 and the ASIC 13
are mounted. In the present embodiment, the MEMS chip 12 and the ASIC 13 are both flip-chip
mounted, and both are electrically connected by the wiring pattern formed on the circuit board
14. In the present embodiment, the MEMS chip 12 and the ASIC 13 are flip-chip mounted.
However, the present invention is not limited to this configuration. For example, the MEMS chip
12 and the ASIC 13 may be mounted using wire bonding.
[0032]
The acoustic resistance unit 15 is provided above the first sound hole 111. In the present
embodiment, the acoustic resistance portion 15 is formed by arranging a sheet-like acoustic
03-05-2019
9
resistance member formed in a substantially circular shape in a plan view so as to close the first
sound hole 111 provided in the housing 11. As the acoustic resistance member, for example, a
mesh member formed of a resin such as polyester or nylon or stainless steel is used. The opening
of the mesh member is, for example, about 20 to 100 μm, and its thickness is, for example,
about 0.1 mm. However, these are merely examples, and the opening, the number of meshes, the
thickness, and the like of the mesh member used as the acoustic resistance member are
appropriately selected according to the purpose, and are not limited to the above. Here, the
number of meshes refers to the number of meshes in one inch (25.4 mm). Further, the opening
refers to a value obtained by the following equation when the diameter of a line forming a mesh
is defined as a wire diameter. Opening (μm) = (25400 mesh number)-Wire diameter
[0033]
In the present embodiment, the acoustic resistance member constituting the acoustic resistance
portion 15 is formed in a substantially circular shape in plan view, but is not limited to this, and
the shape may be changed as appropriate, for example, a substantially rectangular shape in plan
view It is good also as etc.
[0034]
The acoustic resistance unit 15 is provided to adjust the frequency characteristic of the first
sound introducing space 113.
This is to reduce the difference between the frequency characteristic of the first sound
introducing space 113 and the frequency characteristic of the second sound introducing space
114. Hereinafter, the reason for providing such an acoustic resistance part 15 is demonstrated in
detail.
[0035]
First, referring to FIG. 5, the directivity characteristic required of the microphone unit 1 of the
present embodiment will be described. Here, as shown in FIG. 5A, the directions connecting the
first sound hole 111 and the second sound hole 112 are set as the directions of 0 ° and 180 °.
Further, an intermediate point between the first sound hole 111 and the second sound hole 112
is set to M.
03-05-2019
10
[0036]
In this case, as shown in FIG. 5B, assuming that the distance between the sound source and the
middle point M is constant, when the sound source is in the direction of 0 ° or 180 °, the
diaphragm 122 is used. It is required that the applied sound pressure (pf-pb) be maximized. On
the other hand, it is required that the sound pressure (pf−pb) applied to the diaphragm 122 be
minimum (0) when the sound source is in the direction of 90 ° or 270 °. That is, the
microphone unit 1 of the present embodiment has a property (bi-directional characteristic) that
is easy to receive the sound waves incident from the directions of 0 ° and 180 °, and hard to
receive the sound waves incident from the directions of 90 ° and 270 °. Is desired. The
symmetry of the directivity as shown in FIG. 5 (b) is related to the background noise suppression
performance, and it is desirable for the microphone unit 1 to have directivity with good
symmetry over the entire range of the used frequency range. Be
[0037]
FIG. 6 is a graph for explaining problems in the case where the acoustic resistance unit 15 is not
provided in the microphone unit 1 of the present embodiment. In FIG. 6, the horizontal axis
(logarithmic axis) is the frequency, and the vertical axis is the output of the microphone. Further,
in FIG. 6, a graph (a) indicated by a solid line shows frequency characteristics in the case where
the acoustic resistance portion 15 is not provided in the microphone unit 1 and the sound wave
is prevented from being incident from the second sound hole 112. . Further, in FIG. 6, a graph (b)
indicated by a broken line shows frequency characteristics in the case where the acoustic
resistance portion 15 is not provided in the microphone unit 1 and the sound wave is not
incident from the first sound hole 111 .
[0038]
In addition, in obtaining the data of FIG. 6, the sound source is set as the fixed position of the
direction which shifted | deviated from 90 degrees and 270 degrees (refer Fig.5 (a)). Further,
when obtaining data of each frequency, the amplitude (sound pressure) of the sound wave is the
same.
[0039]
03-05-2019
11
Here, a case is considered where the microphone unit is required to exhibit the bi-directional
characteristics shown in FIG. 5B at all frequencies in the operating frequency range (for example,
100 Hz to 10 kHz). In this case, assuming that the sound source is incident on the microphone
unit with the sound source being shifted from 90 ° and 270 °, the frequency changes between
graph (a) and graph (b) in FIG. However, it is required to maintain a constant output difference.
The constant output difference is a value determined according to the difference between the
distance from the sound source to the first sound hole 111 and the distance from the sound
source to the second sound hole 112. In this respect, in the experimental result shown in FIG. 6,
the graph (a) and the graph (b) maintain a constant output difference up to a frequency of about
100 Hz to 6 kHz. However, in the high frequency band exceeding approximately 6 kHz, the
above-mentioned constant output difference does not occur, and a reversal of the magnitude of
the output value is also observed between graph (a) and graph (b).
[0040]
The above-mentioned tendency in the high frequency band may be attributed to the difference in
frequency characteristics between the first sound introducing space 113 and the second sound
introducing space 114. That is, in the microphone unit 1 of the present embodiment, the ASIC 13
is disposed in the first sound introducing space 113 for the purpose of downsizing. For this
reason, the imbalance between the volume of the first sound introducing space 113 and the
volume of the second sound introducing space 114 is increased, and the difference in the
frequency characteristics between the first sound introducing space 113 and the second sound
introducing space 114 is It is considered to have occurred. And, it is considered that the result as
shown in FIG. 6 results from this difference in frequency characteristics. Therefore, in the
microphone unit 1 of the present embodiment, the acoustic resistance unit 15 is provided to
adjust the frequency characteristics of the first sound introducing space 113, and the frequency
characteristics of the first sound introducing space 113 and the second sound introducing space
114. To reduce the difference between
[0041]
As can be seen from the results shown in FIG. 6 described above, in the case where the acoustic
resistor 15 is not provided in the microphone unit 1 of the present embodiment, desired bidirectional characteristics (FIG. 5 (FIG. Although the characteristics shown in b) can be obtained,
the desired bi-directional characteristics can not be obtained on the high frequency side (the
03-05-2019
12
frequency side higher than approximately 6 kHz). For this purpose, as a characteristic of the
acoustic resistance portion 15 provided in the microphone unit 1, for example, it is conceivable
to provide a characteristic that exerts an effect of becoming a microphone output shown by a
broken line in FIG. That is, it has little effect on the low frequency side sound, and selectively acts
on the high frequency (for example, frequency between 6 kHz and 20 kHz) side (decreases the
output on the high frequency side). It is conceivable to provide an acoustic resistance portion 15.
[0042]
In addition, FIG. 7 is a figure for demonstrating the characteristic of the acoustic resistance part
15 with which the microphone unit 1 of this embodiment is provided. The horizontal axis in FIG.
7 is a logarithmic axis.
[0043]
FIG. 8 is a figure for demonstrating the effect at the time of arrange | positioning an acoustic
resistance member so that the sound introduction space may be obstruct | occluded. In FIG. 8,
the horizontal axis (logarithmic axis) is the frequency, and the vertical axis is the output of the
microphone. Further, in FIG. 8, graph (a) shows the result in the case where the acoustic
resistance member is not arranged, and graph (b) shows the result in the case where the acoustic
resistance member a is arranged, and graph (c) shows different characteristics from the acoustic
resistance member a. It is a result at the time of arrange | positioning the acoustic resistance
member b to have. Although FIG. 8 shows the result in the case of using a microphone unit
having a configuration different from that of the microphone unit 1 of the present embodiment,
the tendency obtained here also applies to the microphone unit 1 of the present embodiment.
[0044]
As shown in FIG. 8, by arranging the acoustic resistance members a and b so as to close the
sound introducing space, the microphone output is not substantially changed on the low
frequency band side, and the microphone output is selectively selected on the high frequency
band side. It can be seen that it can be attenuated. Further, it is also understood that the
attenuation of the microphone output at each frequency can be changed by changing the
characteristics of the acoustic resistance member. Therefore, as in the microphone unit 1 of the
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13
present embodiment, by providing the acoustic resistance portion 15 so as to close the first
sound introducing space 113, the frequency characteristics of the first sound introducing space
113 and the second sound introducing space 114 can be obtained. It can be seen that it is
possible to reduce the difference.
[0045]
The main factors that determine the characteristics of the acoustic resistance member formed of
the sheet-like mesh member are the number of meshes (corresponding to the density of the holes
formed in the mesh member) and the size of the openings of the mesh (the holes of the mesh
member) And thickness. Therefore, it is possible to obtain an acoustic characteristic member
having desired characteristics by adjusting these factors.
[0046]
Here, the effect in the case of using the microphone unit 1 of the present embodiment configured
as described above will be described.
[0047]
For example, when the microphone unit 1 of the present embodiment is applied to a close-talking
type voice input device, the user's voice is generated from the vicinity of the first sound hole 111
and the second sound hole 112.
As described above, the user's voice generated near the vibrating membrane 122 causes a large
difference in sound pressure due to the difference in the distance to the vibrating membrane
122. Therefore, a sound pressure difference is generated between the upper surface 122a and
the lower surface 122b of the diaphragm 122 of the microphone unit 1 by the voice of the user,
and the diaphragm 122 vibrates.
[0048]
On the other hand, noise such as background noise generates a sound wave at a position farther
from the first sound hole 111 and the second sound hole 112 than the user's voice. As described
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14
above, noise generated at a position far from the vibrating membrane 122 hardly causes a
difference in sound pressure even if there is a difference in the distance to the vibrating
membrane 122. For this reason, the sound pressure difference due to noise is canceled in the
vibrating membrane 122.
[0049]
Therefore, in the microphone unit 1, the vibrating membrane 122 can be regarded as vibrating
only by the voice of the nearby user. Therefore, the electrical signal output from the microphone
unit 1 can be regarded as a signal representing only the user's voice from which noise has been
removed. That is, according to the microphone unit 1 of the present embodiment, it is possible to
obtain user's voice from which noise is removed.
[0050]
Further, in the microphone unit 1 of the present embodiment, since the ASIC 13 for processing
the electric signal generated based on the vibration of the vibrating membrane 122 is disposed in
the first sound introducing space 113, the size can be reduced.
[0051]
When the ASIC 13 is disposed in the first sound introducing space 113, the volume imbalance
between the first sound introducing space 113 and the second sound introducing space 114
makes it possible to obtain desired bi-directional characteristics particularly in a high frequency
band. Noise suppression performance can not be obtained.
However, in the microphone unit 1 of the present embodiment, the difference in the frequency
characteristics between the first sound introducing space 113 and the second sound introducing
space 114 can be reduced by providing the acoustic resistance portion 15, so on the high
frequency side It is possible to obtain good noise suppression performance. That is, it can be said
that the microphone unit 1 of the present embodiment is a compact and high-performance
microphone unit.
[0052]
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15
The embodiment shown above is an example, and the microphone unit of the present invention is
not limited to the composition of the embodiment shown above. Various changes may be made to
the configuration of the embodiment described above without departing from the object of the
present invention.
[0053]
For example, in the embodiment described above, the acoustic resistance member is disposed
above the first sound hole 111 to form the acoustic resistance portion 15. However, the acoustic
resistance member (acoustic resistance portion) may be provided at a position where the sound
wave from the first sound hole 111 to the vibrating film 122 through the first sound introducing
space 113 passes. That is, the acoustic resistance member may be disposed so as to close at least
a part of the path from the first sound hole 111 to the upper surface 122 a of the vibrating
membrane 122. In the case of the present embodiment, the acoustic resistance member blocks
the entire path from the first sound hole 111 to the upper surface 122 a of the diaphragm 122.
[0054]
Further, in the embodiment described above, the acoustic resistance member is attached to the
housing 11 in the acoustic resistance portion 15. However, the configuration of the acoustic
resistance portion 15 is not limited to this, and may be configured by processing the housing 11,
for example. Specifically, for example, as shown in FIG. 9, the first sound hole 111 may be an
assembly of a plurality of small through holes, and the microphone unit 21 may be configured
such that the first sound hole 111 doubles as the acoustic resistance portion 15. good.
[0055]
In the embodiment described above, the acoustic resistance portion 15 is provided only on the
side of the first sound hole 111. However, the present invention is not limited to this
configuration, and in addition to the first sound hole 111 side, the sound resistance portion may
be provided on the second sound hole 112 side. In the case of this configuration, an acoustic
resistance portion is provided to adjust the frequency characteristics of both the first sound
introducing space 113 and the second sound introducing space 114 to match the frequency
characteristics of both.
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[0056]
As a specific example of the configuration in which the acoustic resistance portion is provided on
the second sound hole 112 side in addition to the first sound hole 111 side, for example, as
shown in FIG. It is possible to provide a configuration (microphone unit 31) in which one acoustic
resistance unit 15, 16 is provided. The two acoustic resistance members having different
characteristics may be made of, for example, different materials, or may be made of the same
material, for example, with different parameters such as thickness.
[0057]
As another specific example, as shown in FIG. 11, for example, the first sound hole 111 and the
second sound hole 112 may be closed by only one acoustic resistance member (integral body)
(microphone unit 41). In the case of this configuration, for example, as shown in FIG. 11, the
stepped portion 17a is provided, and the acoustic resistance portion 17 is configured such that
the thickness of the acoustic resistance member differs between the first sound hole 111 side
and the second sound hole 112 side. It is good. Thus, the frequency characteristics of both the
first sound introducing space 113 and the second sound introducing space 114 can be adjusted
to reduce the difference between the frequency characteristics of the first and second sound
introducing spaces 113 and 114.
[0058]
Moreover, in the embodiment shown above, although the acoustic resistance part 15 was
provided only in the 1st sound hole 111 side, it is good also as a structure which provides the
acoustic resistance part 15 only in the 2nd sound hole 112 side. For example, if the frequency
characteristic of the second sound introducing space 114 is adjusted, the frequency
characteristic of the first sound introducing space 113 and the second sound introducing space
114 are different from the case of the present embodiment by changing the space shape of the
microphone unit 1. In some cases, it is possible to reduce the difference from the frequency
characteristics of
[0059]
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17
Further, in the embodiment described above, the diaphragm 122 (diaphragm) is disposed in
parallel with the surface 11 a of the housing 11 in which the sound holes 111 and 112 are
formed. However, the present invention is not limited to this configuration, and the diaphragm
may be configured not to be parallel to the surface on which the sound hole of the housing is
formed.
[0060]
In addition, in the microphone unit 1 shown above, a so-called condenser type microphone is
adopted as the configuration of the microphone (the MEMS chip 12 corresponds) having the
diaphragm. However, the present invention can of course be applied to a microphone unit
adopting a configuration other than a condenser type microphone as a configuration of a
microphone having a diaphragm. As a configuration other than the capacitor type microphone
having a diaphragm, for example, a dynamic type (dynamic type), an electromagnetic type
(magnetic type), a piezoelectric type microphone or the like can be mentioned.
[0061]
The microphone unit of the present invention is suitable for use in, for example, voice
communication devices such as mobile phones and transceivers, information processing systems
using techniques for analyzing input voice such as voice authentication systems, and recording
devices.
[0062]
These are schematic perspective views which show the structure of the microphone unit of this
embodiment.
FIG. 2 is a schematic cross-sectional view at a position A-A in FIG. These are schematic sectional
drawings which show the structure of the MEMS chip with which the microphone unit of this
embodiment is provided. These are figures for demonstrating the circuit structure of ASIC with
which the microphone unit of this embodiment is provided. These are figures for demonstrating
the directivity characteristic requested | required of the microphone unit of this embodiment.
These are graphs for demonstrating the problem when it is set as the structure which does not
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provide an acoustic resistance part in the microphone unit of this embodiment. These are figures
for demonstrating the characteristic of the acoustic resistance part with which the microphone
unit of this embodiment is provided. These are figures for demonstrating the effect at the time of
arrange | positioning an acoustic resistance member so that the sound introduction space may be
obstruct | occluded. These are figures for demonstrating the modification of the microphone unit
of this embodiment. These are figures for demonstrating the modification of the microphone unit
of this embodiment. These are figures for demonstrating the modification of the microphone unit
of this embodiment.
Explanation of sign
[0063]
DESCRIPTION OF SYMBOLS 1, 21, 31, 41 Microphone unit 11 Housing | casing 12 MEMS chip
13 ASIC (electric circuit part) 15 Acoustic resistance part 111 1st sound hole 112 2nd sound
hole 113 1st sound introduction space 114 2nd sound introduction space 122 Vibration Film
(diaphragm) 122 a upper surface of diaphragm (first surface of diaphragm) 122 b lower surface
of diaphragm (second surface of diaphragm)
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