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JPH057390

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DESCRIPTION JPH057390
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
mounting structure of a microphone unit mounted in a thin and small-volume housing.
[0002]
2. Description of the Related Art FIG. 13 is a cross-sectional view showing the mounting structure
of a conventional microphone unit disclosed in, for example, Japanese Patent Application LaidOpen No. 63-232798. In the figure, 10 is a housing, 11 is a differential microphone unit
(hereinafter referred to as "microphone unit"), 11a is a plurality of small openings formed on the
back surface, 15 is a front sound hole, 16 is a front sound hole A back air chamber, 17 is a front
air chamber, 18 is a back sound hole, and in this conventional example, a front air chamber 17
and a back air chamber 16 of similar size are provided on the front and back of the microphone
unit 11, A front sound hole 15 and a back sound hole 18 are provided on the same surface of the
body 10.
[0003]
Further, in the conventional example disclosed in Japanese Utility Model Application Publication
No. 57-60306, the microphone unit is covered with a wire mesh to make the back surface close
to an open state so that the directivity of the microphone unit is not lost.
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[0004]
Also, in a portable recorder and video tape recorder, the microphone unit is wrapped in a
breathable open-celled urethane resin material and attached to the outside of the case.
[0005]
Since the conventional mounting structure of the unidirectional microphone unit is configured as
described above, it is possible to cover rain on the back surface of the microphone unit and
prevent it from invading the inside of the microphone unit. It is difficult to prevent, and it is
difficult to mount with a battery, an electronic circuit component or the like in a thin and small
case, and there are further problems such as a restriction on the design of the case.
[0006]
The present invention has been made to solve the above-mentioned problems, and the
microphone unit can be mounted in a small space in a thin and small housing to maintain
directivity, and further, it is possible to restrict the design. The object is to obtain a mounting
structure of a small number of microphone units.
[0007]
In the microphone unit mounting structure according to the present invention, a small diameter
front sound hole is provided on the front of the differential microphone unit mounted inside the
housing, and a predetermined volume is provided on the rear surface. An air chamber is
provided, and a rear sound hole connected to the rear air chamber is provided so as to open on a
housing surface different from the housing surface in which the front sound hole is formed.
[0008]
Further, the present invention is characterized in that a plurality of back sound holes are
provided.
[0009]
Also, the present invention is characterized in that the microphone unit is disposed in the lower
central portion of the housing formed wide, and the back sound hole is formed in the lower or
lower surface of the back surface of the housing. Do.
[0010]
Further, according to the present invention, an airtight sealing member for airtightly sealing
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between the space in the housing in which the receiver is disposed and the space in the housing
in which the microphone unit is disposed and the back air chamber is provided. It is
characterized by
[0011]
Further, the present invention is characterized in that a drip-proof member disposed between the
front surface of the microphone unit and the front sound hole is provided.
[0012]
In the present invention, the back air chamber and the back sound hole change the amplitude
and the phase of the sound wave coming from the outside of the housing to guide the sound
wave to the back of the microphone unit, so in a thin and small volume housing Also, the
directivity of the microphone unit can be obtained.
[0013]
In addition, the microphone unit is disposed at the lower central portion of the widely formed
housing, and the back sound hole is formed on the lower or lower surface of the back of the
housing, so the front sound hole or back sound with the fingertip at the time of operation There
is less risk of blocking the holes.
[0014]
In addition, since the space in the housing in which the receiver is disposed and the space in the
housing in which the microphone unit is disposed and the back air chamber are airtightly sealed
by the airtight sealing member, howling occurs Can be prevented.
[0015]
Further, since the drip-proof member is provided between the front surface of the microphone
unit and the front sound hole, it is possible to prevent water droplets such as rain from entering
the microphone unit from the front sound hole.
[0016]
EXAMPLES Example 1
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Hereinafter, a first embodiment of the present invention will be described with reference to the
drawings.
In FIG. 1, the microphone unit 11 is held by a soft rubber holder 12 and is housed in a housing
10 made of a strong material that can be carried outdoors.
A front sound hole 15 having a diameter of about 2 mm is provided in the partial housing 10
corresponding to the front of the microphone unit 11, and a rear air chamber 16 of about 0.04
cc is provided on the back of the microphone unit 11. A rear sound hole 18a of about 4 mm 2
connected to the rear air chamber 16 is formed on the lower side surface of the housing 10.
[0017]
The Ni-Cd battery 14 with a thickness of about 6 mm is mounted behind the partition plate 10a,
and the microphone unit 11 having a diameter of about 6 mm and a thickness of about 5 mm is
used. It is configured to a thin, low volume phone.
[0018]
Next, the acoustic operation of this embodiment will be described.
The sound wave coming from the front direction of the microphone unit 11 (this is taken as 0 °)
vibrates the diaphragm of the microphone unit 11 through the front aperture 15, and part of the
sound wave is diffracted along the housing 10 And the amplitude and phase change to reach the
back sound hole 18a.
The sound wave that has reached the back sound hole 18 a is affected by the stiffness of the
back air chamber 16, acoustic resistance, and the like, and the amplitude and phase thereof
further change to reach the back surface of the microphone unit 11.
[0019]
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This sound wave enters the microphone unit 11 through a plurality of small apertures formed on
the back surface of the microphone unit 11, and vibrates the diaphragm from behind.
Therefore, the output of the microphone unit 11 is the difference between the vibration due to
the sound wave passing through the front sound hole 15 and the vibration due to the sound
wave passing through the back sound hole 18 a.
[0020]
Next, the influence of the front sound hole 15 and the back sound hole 18a on the vibration and
phase of the sound wave will be described.
The front sound hole 15 is mainly affected by the acoustic resistance and inertance of the sound
hole, but if the sound hole area has a diameter equivalent to 1 to 3 mm, it is experimentally
confirmed that the influence is small There is.
[0021]
On the other hand, the sound waves passing through the back sound hole 18a are affected by the
back sound hole 18a and the back air chamber 16, so they are more complicated than that of the
front opening 15, and the degree of influence is also large.
[0022]
The acoustic equivalent circuit of the back sound hole 18a and the back air chamber 16 is
represented as shown in FIG.
In the figure, F2 is the sound pressure at the opening surface of the back sound hole 18a, r2 is
the acoustic resistance of the back sound hole 18a, m2 is the inertance of the back sound hole
18a, s is the stiffness of the back air chamber 16 and Z180 is the microphone unit 11 The
acoustic impedance when viewed from the back, ξ 2 is the volume velocity of air at the back
sound hole 18 a, and ξ 180 is the volume velocity at the back of the microphone unit 11.
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[0023]
The volume velocity ξ180 of the back of the microphone unit 11 is ξ180 = F2 / (Z180 + Z2 +
Z180 ・ Z2 ・ jω / s) from FIG. 2 (1) However, the acoustic impedance Z2 of the back sound
hole 18a is Z2 = (r2 + J ω m 2) ω is an angular frequency.
[0024]
A small hole of about 1 mm in diameter is made on the back of the microphone unit 11, and its
acoustic resistance is quite large.
Since the back sound hole 18a is larger than the back small hole of the microphone unit 11, | Z2
/ Z180 | <1
[0025]
Also, the inertance m2 of the back sound hole 18a is smaller than the acoustic resistance r2.
Therefore, equation (1) is approximated as the following equation.
| Ξ 180 | | | F 2 / Z 180 | · [1 / {1 + (ω r 2 / s) 2} 1/2] (2) In the above equation, | F 2 / Z 180 |
The second term shows the degree of influence of the back sound hole 18 and the back air
chamber 16 on the volume speed.
[0026]
It is known that the acoustic resistance and stiffness of the second term can be calculated based
on the opening area and shape of the back sound hole 18a and the volume of the back air
chamber 16. For example, the opening area of the back sound hole 18a Is a size corresponding to
a diameter of 1 to 10 mm, and the volume of the back air chamber 16 is about 0.02 cc to 10 cc,
the following equation (ω · r 2 / s) 2 <in the voice band (300 to 3000 Hz) 1 (3) holds, the volume
velocity at this time | ξ180 | is 0.7 | F2 / Z180 | <| <180 | <F2 / Z180 | (4)
[0027]
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The amplitude of this volume velocity is at least 0.7 times or more of the amplitude at the time of
opening, the attenuation by the back air chamber 16 and the back sound hole 18a is small, and
the influence on the directivity is also small.
[0028]
As in this embodiment, in order to obtain directivity by incorporating the small microphone unit
11 in the thin and small volume housing 10, providing a large air chamber is a space inside the
housing 10. It is disadvantageous in terms of efficient use.
[0029]
In addition, in the method of incorporating two microphone units inside the housing and
obtaining directivity by the difference output, an internal volume for at least two microphone
units is required, but as in this embodiment, 1 If two microphone units are built in and the
volume of the back air chamber 16 is set smaller than the volume of the microphone unit 11, the
most efficient use of space can be obtained, and good directivity can be obtained.
[0030]
As the microphone unit 11 having a diameter of 6 mm, a thickness of 5 mm to a diameter of 10
mm, and a thickness of about 10 mm can be used, the volume of the back air chamber 16 in this
case is about 0.1 cc to 0.8 cc. Although the practical volume range of the back air chamber 16 is
0.02 cc to 0.8 cc in consideration of this, equation (4) holds also in this volume range, and the
amplitude change of volume velocity is small. Deterioration of directivity at that time is expected
to be the same degree, and the degree of deterioration falls within -3 dB to 0 dB in sound
pressure display.
[0031]
On the other hand, the directivity when the microphone unit 11 is open is -6 to -10 dB at 1 kHz,
so -3 to -7 dB even if the influence of the back air chamber 16 and the back sound hole 18 is
subtracted -3 dB to 0 dB Yes, practical directivity is obtained.
[0032]
3 shows the case where the front sound hole 15 has a diameter of 2.4 mm, the volume of the
back air chamber 16 is about 0.04 cc, and the area of the back sound hole 18a is 4 mm 2 as
described above in the mounting structure shown in FIG. The horizontal axis is the frequency,
and the vertical axis is the relative sensitivity of the microphone unit 11. The microphone
sensitivity to the sound source in the front direction (0 °) and the sound source in the back
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direction (180 °) The sensitivity to the microphone is shown, the sensitivity in the back
direction is small, and practically sufficient directivity is obtained.
[0033]
In this embodiment, the back sound hole 18a is provided on the lower side surface of the
housing 10. However, even if the user holds the lower side of the housing 10 to make a call, the
back sound hole 18a is closed by the palm. There is an advantage that there is little risk of
deterioration of directivity due to peeling.
[0034]
The back sound hole 18a operates in the same manner as long as it is provided on a housing
surface other than the housing surface in which the front sound hole 15 is provided, so the
position of the back sound hole 18a and the mounting position of the microphone unit 11 are
Since the right and left ends of the body 10, the center, and the left and right sides may be used,
restrictions on the design of the housing are reduced.
[0035]
Example 2
FIG. 4 is a cross-sectional view of a second embodiment of the present invention, in which a part
of the battery 14 is cut away to provide a back sound hole 18b, and a back air chamber 16 is
formed in an L shape.
As described above, even if the back air chamber 16 is bent in an L shape, there is no significant
difference in the value of stiffness if the volume is the same, so the area of the back sound hole
18b and the volume of the back air chamber 16 are shown in FIG. The same effect can be
obtained by selecting the same value as the embodiment shown in FIG.
[0036]
Example 3
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FIG. 5 is a cross-sectional view of a third embodiment of the present invention, in which an
acoustic tube 19 for guiding a sound wave is attached to a part of the battery 14 and a back
sound hole 18c is formed at the tip.
In this embodiment, the total volume of the back air chamber is the sum of the volume of the
acoustic tube 19 and the volume of the back air chamber 16 of the microphone unit 11, and the
predetermined total volume satisfying the equation (3), the predetermined aperture area The
same effects as those of the respective embodiments can be obtained.
[0037]
Example 4
FIG. 6 is a cross-sectional view of a fourth embodiment of the present invention, in which a linear
back sound hole 18 d is provided from the back surface of the microphone unit 11 to the back
surface of the housing 10.
In this embodiment, since the distance between the back sound hole 18d and the front sound
hole 15 is large, there is an effect that the frequency can be offset to a lower frequency. The
volume of the back air chamber 16 and the area of the back sound hole 18d are shown in FIG. If
you choose the same value as, you will get the same effect.
[0038]
Example 5
FIG. 7 is a cross-sectional view of a fifth embodiment of the present invention, in which a back
sound hole 18a is added to the embodiment shown in FIG.
In this embodiment, since the amplitudes and phases of the sound waves reaching the two rear
sound holes 18a and 18b are different, the volume velocity ξ 180 of the back surface of the
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microphone unit 11 corresponding to the equation (1) is It will be.
[0039]
ξ180 = F2 / (Z180 + Z23 + Z180180Z23 ・ jω / s) (5) Z23 = (r2 + jω · m2) (r2 + jω · m3) / {r2
+ r3 + jω (m2 + m3)} ω is the angular frequency, and the back surface When the inertances m2
and m3 of the sound holes 18a and 18b are smaller than the acoustic resistances r2 and r3 and |
Z23 / Z180 | << 1, the equation (5) is approximated as the following equation.
| Ξ 180 | = | F 2 / Z 180 | · [1 / {1 + (ω · r 23 / s) 2} 1/2] (6) r 23 = r 2 · r 3 / (r 2 + r 3)
[0040]
If the opening area of the back sound holes 18a and 18b is a size equivalent to 1 to 10 mm in
diameter as in the embodiment of FIG. 1, and the volume of the back air chamber 16 is about
0.05 cc to 10 cc. For example, in the voice band (300 to 3000 Hz), the following equation (ω ·
r23 / s) 2 (7) holds, and the volume velocity | ξ 180 | at this time becomes as in equation (4),
the back surface Since the attenuation by the air chamber 16 and the rear sound holes 18a and
18b is small and the influence on the directivity is also small, practical use of the rear air
chamber 16 in the case of using the microphone unit 11 of the same size as the first embodiment
of FIG. If the volume of the rear air chamber 16 and the size of the two rear sound holes 18a and
18b satisfy the equation (7), the basic volume range is 0.02 cc to 0.8 cc as in the first
embodiment of FIG. The same directivity can be obtained.
[0041]
In the fifth embodiment, since the two rear sound holes 18a and 18b are provided at a distance
from each other, there is an advantage that the directivity is not easily deteriorated due to the
two rear sound holes 18a and 18b being closed simultaneously with the palm. can get.
[0042]
In addition, even if the size of the two back sound holes 18a and 18b is changed, the synthesized
sound resistance may be within the predetermined range, and the back sound hole at a position
easy to see is small in design and a position difficult to notice Since it is sufficient to enlarge the
back surface sound hole, the degree of freedom in design of the case is further improved.
03-05-2019
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[0043]
Example 6
FIG. 9 is a cross-sectional view of the sixth embodiment of the present invention, in which the
back sound hole 18a is added to the third embodiment shown in FIG. 5, and the same directivity
as the fifth embodiment of FIG. Is obtained.
[0044]
In Examples 5 and 6, two back sound holes are provided, but the number may be three or more.
In this case, the acoustic impedance Z is a parallel connection of the acoustic impedances of the
respective back sound holes. Therefore, the opening area may be determined by the same
method.
[0045]
In addition, even in the structure in which the back air chamber 16, the back sound holes 18a to
18d, and the acoustic tube 19 are integrally formed of synthetic resin or metal, the air chamber
and the sound holes have the same acoustic operation. Play.
[0046]
Example 7
FIG. 10 is a cross-sectional view of a seventh embodiment of the present invention, in which the
housing 10 comprises a front housing 19, a rear housing 20 and a partition plate 10a following
it, and is formed in the lower central portion of the front housing 19. A receiver 23, a liquid
crystal display unit 24, and an operation button unit 25 are disposed in the storage unit 22
divided by the cylindrical protrusion 21 for storing the microphone unit 11, and the storage unit
22 and the back air chamber 16 are provided. The space is hermetically sealed by the hermetic
sealing member 26.
[0047]
Reference numeral 27 denotes a drip-proof member, which is made of, for example, a sheet
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material obtained by sintering polyethylene, and has sufficient air permeability while preventing
intrusion of raindrops and water droplets, and the front surface of the microphone unit 11 and
the front sound hole 15 It is disposed between.
[0048]
11 is a front view of the microphone unit mounting portion of FIG. 10 in the X1-X2 line arrow
direction; 28 is a sounder, 29 is a sounder storage portion formed in the front case 19, 30 is a
sounder rubber holder, 31 is a front case The sounder sound holes formed in the body 19 are
configured to be in close contact with the sounder sound holes 31 and the sound holes of the
sounder 28 so that the sound pressure loss of the sounder 28 is reduced.
[0049]
According to the seventh embodiment, the inside of the housing 22 where the handset 23 is
disposed and the microphone unit 11 including the back air chamber 16 are arranged by the
airtight sealing member 26 airtightly held by the bulging part 26a. Since the space with the
space provided is airtightly closed, the occurrence of howling is prevented.
[0050]
In addition, since the front sound hole 15 is closed by the drip-proof member 27, it is possible to
prevent raindrops and water droplets entering from the front sound hole 15 from entering the
microphone unit 11.
[0051]
Example 8
FIG. 12 is a cross-sectional view of the eighth embodiment of the present invention, in which the
hermetic sealing member 26 is integrally formed with the rubber holder 30.
The rubber holder 30 is suitably made of a sufficiently soft material because the weight of the
microphone unit 11 is as low as about 1 g. For example, silicone rubber having a hardness of 40
° to 70 ° HSA is suitable.
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[0052]
As described above, according to the present invention, a front sound hole is provided in a
portion corresponding to the front of the microphone unit of the housing accommodating the
differential type microphone unit, and the microphone is provided on the back of the microphone
unit. In addition to providing a back air chamber having a volume smaller than that of the unit
and providing a back sound hole communicating with the back air chamber on the housing
surface of the direction different from the housing surface provided with the front sound hole In
addition, even in the case of a small-volume housing, directivity can be obtained, and an
advantage can be obtained that the degree of freedom in design of the housing is increased.
[0053]
In addition, since the back sound holes are provided in a plurality, it is difficult to cause
deterioration of directivity due to the back sound holes being closed with the palm, and further,
there is an advantage that the degree of freedom in design of the housing is increased. can get.
[0054]
In addition, since the microphone unit is disposed at the lower central portion of the housing
formed wide, and the back sound hole is formed on the back or lower surface of the lower part of
the housing, the front sound hole or back sound hole with the fingertip at the time of operation Is
less likely to be blocked.
[0055]
Further, since the space in which the handset in the case is disposed and the space in which the
microphone unit is disposed are hermetically sealed, the occurrence of howling is reduced.
[0056]
In addition, since the space between the front sound hole communicating with the microphone
unit and the microphone unit is closed by the drip-proof member having sufficient air
permeability, raindrops and water droplets intrude into the microphone unit from the front
sound hole. Can be prevented.
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