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DESCRIPTION JP2010278888

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DESCRIPTION JP2010278888
A transmitter having high sensitivity in a high sound (high frequency) region and capable of
realizing a wider band compared to the conventional structure is obtained. A front portion is
constituted by a space defined by a mouthpiece wall portion 13 having an outer peripheral shape
of a first truncated cone on an inner wall 13a and a peripheral wall 14 having an outer
peripheral shape on an inner wall 14a of a second truncated cone. A plurality of air chambers 12
and a plurality of microphone units 11 facing the mouthpiece wall portion 13 and arranged to
face the space of the front air chamber 12 and communicating with the peripheral end of the
space of the front air chamber 12 The sound hole 15 is a transmitter provided in the mouthpiece
wall portion 13. [Selected figure] Figure 1
Transmitter
[0001]
The present invention relates to a transmitter used in a handset or the like of a telephone, and
more particularly to a transmitter which has excellent sensitivity in a high-tone (high frequency)
region and realizes a wide band.
[0002]
2. Description of the Related Art In recent years, communication quality has been improved to
perform high-quality (clear) transmission of voice and the like by performing communication
using a broadband circuit such as an IP circuit.
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According to the IP line, it is possible to use a voice transmission band of up to 20 kHz, but in
order to improve the speech quality, it is necessary to realize a wide band of the transmitter
connected to the line.
[0003]
As shown in FIGS. 11 and 12, the transmitter 2 used in the handset 1 of the telephone set has a
front air chamber 22 with a cylindrical space in front of the microphone 21 having excellent
sensitivity in the high frequency (high frequency) region. By providing, voices (sound waves)
enter the front air chamber 22 from the plurality of sound holes 24 formed in the mouthpiece
wall portion 23, and reach the sound receiving surface of the microphone 21 through the space
of the front air chamber 22. In order to achieve a wide band. That is, the high air (high
frequency) region of the sound wave is emphasized by the front air chamber 22, and the
transmitter 2 can be broadened. In this case, the sensitivity to the frequency in the transmitter 2
is as shown in FIG. 13, and the high frequency (fH), which is the upper limit frequency that can
output the electric signal without causing a decrease in sensitivity, is shown in the following
equation (A) Thus, it is known that it is proportional to the square root of the sum (Sm) of the
opening area of the sound hole 24 and inversely proportional to the square root of the volume
(VF) of the front air chamber 22 (α is a constant). In the formula (A), in order to obtain a high
upper limit frequency (fH), it is necessary to increase the sum (Sm) of the opening area of the
sound hole 24 or to reduce the volume of the front air chamber 22. fH = (α / 2π) √ (Sm / VF)
(Formula A)
[0004]
When downsizing the transmitter 2 provided with the front air chamber 22 having the shape as
described above, the volume of the front air chamber 22 can be made small, which is
advantageous for broadening the bandwidth, while the area of the mouthpiece wall portion 23 is
Because the size of the sound hole 24 decreases, the total sum of the open areas of the sound
holes 24 decreases, which causes an obstacle to broadening the bandwidth. Further, the front air
chamber 22 needs to play a role of protecting the microphone 21 from static electricity by
securing the distance L between the sound hole 24 formed in the mouthpiece wall portion 23
and the microphone 21, so the front air chamber There is also a limit to reducing the volume of
22. When the area of the mouthpiece wall 23 of the transmitter 2 is increased to increase the
sum of the opening areas of the sound holes 24, there is a limit to the reduction of the volume of
the front air chamber 22, and a wide band is realized. It becomes an obstacle.
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[0005]
Therefore, in order to realize a microphone for achieving a wide band while protecting the
microphone from static electricity, as a structure for reducing the volume of the front air
chamber by securing a distance between one end face of the front air chamber and the
microphone, The structure of the transmitter described in 1 has been proposed.
[0006]
As shown in FIG. 14, this transmitter has a substantially mortar-shaped inner wall in which the
side of the mouthpiece wall 23 becomes wider in the space of the front air chamber 22 (the
mouthpiece wall 23 and the side wall of the microphone 21 And the cross section orthogonal to
the line segment connecting the lines from the mouthpiece wall 23 to the area toward the wall on
the microphone 21 side), the distance L between the mouthpiece wall 23 and the microphone 21
is To realize a wide band by reducing the volume of the front air chamber 22 (reducing the
volume of the front air chamber space) while protecting the microphone 21 from static electricity
without shortening as compared with the structure of FIG. 12 (See Patent Document 1).
[0007]
Patent Document 1: Japanese Patent Application Publication No. 2008-154036
[0008]
However, according to the above-described structure of the transmitter 2, there is a problem that
although the wide band can be achieved by reducing the space of the front air chamber 22, there
is a problem that it is not sufficient. It was desired.
[0009]
The present invention has been proposed in view of the above circumstances, and it is an object
of the present invention to provide a transmitter which is excellent in sensitivity in a high sound
(high frequency) region and which can realize wider band as compared with the conventional
structure. There is.
[0010]
In order to achieve the above object, the invention according to claim 1 is characterized in that a
front air chamber formed of a space partitioned and formed by a mouthpiece wall and a
peripheral wall, and a space of the front air chamber facing the mouthpiece wall. And a
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microphone unit disposed to face the front face of the microphone, wherein a plurality of sound
holes communicating with the outermost end of the space of the front air chamber are formed in
the wall of the mouthpiece. And
[0011]
The invention according to claim 2 is the transmitter according to claim 1, wherein the space of
the front air chamber is cylindrical, and the plurality of sound holes are formed in the
mouthpiece wall portion along the circle of the front air chamber. It is characterized by being
done.
[0012]
According to the invention of claim 3, in the transmitter according to claim 1, the space of the
front air chamber has a mouthpiece wall portion having an outer peripheral shape of a first
truncated cone on an inner wall, and a periphery of a second truncated cone It is characterized in
that it is defined by a peripheral wall having a shape on the inner wall.
[0013]
The invention of claim 4 is characterized in that in the transmitter of claim 3, the shape of the
first truncated cone and the shape of the second truncated cone are similar.
[0014]
The invention according to claim 5 is characterized in that, in the transmitter according to claim
3 or claim 4, the mouthpiece wall has a conical recess on the sound hole forming side.
[0015]
The invention according to claim 6 is arranged so as to face the space in the front air chamber,
facing the front air chamber constituted by a space defined by the mouthpiece wall and the
peripheral wall, and the mouthpiece wall. In the transmitter provided with the microphone unit, a
plurality of sound holes communicating with the space of the front air chamber are formed in the
peripheral wall.
[0016]
The invention according to claim 7 is characterized in that a front air chamber constituted by a
space partitioned and formed by a mouthpiece wall, and a microphone facing the space of the
front air chamber facing the mouthpiece wall. In the transmitter equipped with the unit, the
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mouthpiece wall portion is annularly mounted around the front air chamber by being attached
via a support to a microphone attachment plate to which the microphone unit is attached. It is
characterized in that it is formed as a sound hole.
[0017]
According to the transmitter of claim 1, by forming a plurality of sound holes communicating
with the peripheral end of the space of the front air chamber in the mouthpiece wall, the
mouthpiece wall and the microphone unit A wide band can be realized by reducing the volume of
the front air chamber (reducing the volume of the front air chamber space) while securing a
distance to protect the microphone unit from static electricity.
[0018]
In this case, the space of the front air chamber has a cylindrical shape with a low height (claim 2),
a mouthpiece wall portion having an outer peripheral shape of the first truncated cone on the
inner wall, and a second truncated cone With the configuration (claim 3) divided by the
peripheral wall having the peripheral shape on the inner wall, the volume can be reduced.
[0019]
In addition, the configuration in which the shape of the first truncated cone and the shape of the
second truncated cone are similar to each other ensures the reduction in volume of the front air
chamber and the total area of the cross-sectional areas of the sound holes. A wide band can be
efficiently realized by combining contradictory matters in a balanced manner.
[0020]
By providing a conical recess on the sound hole forming side of the mouthpiece wall portion
(claim 5), when the peripheral shape of the first truncated cone in the mouthpiece wall portion is
the inner wall, the mouthpiece wall portion The thickness of the transmitter can be made
uniform, and the appearance of the transmitter can be made a novel design.
[0021]
According to the transmitter of claim 6, by forming a plurality of sound holes communicating
with the space of the front air chamber in the peripheral wall, the distance between the sound
hole and the microphone unit is secured to protect the microphone unit from static electricity.
However, by achieving a reduction in volume of the front air chamber (reduction in volume of the
front air chamber space), broadband can be realized.
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[0022]
According to the transmitter of claim 7, by forming the periphery of the front air chamber as an
annular sound hole, the distance between the annular sound hole and the microphone unit is
secured to protect the microphone unit from static electricity, while the front air is protected.
Broadening the bandwidth can be realized by reducing the volume of the chamber (reducing the
volume of the front air chamber space).
[0023]
An example of embodiment of the transmitter used for the handset is shown, (a) is a sectional
explanatory drawing, (b) is a planar explanatory drawing.
It is a model figure in the case of changing the volume of a front air chamber.
It is a graph which displays the rising degree of high frequency.
It is cross-sectional explanatory drawing which shows the other example of embodiment of a
transmitter.
It is cross-sectional explanatory drawing which shows the other example of embodiment of a
transmitter.
It is cross-sectional explanatory drawing which shows the other example of embodiment of a
transmitter.
It is a model figure in the case of changing the volume of a front air chamber.
It is cross-sectional explanatory drawing which shows the other example of embodiment of a
transmitter.
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The other example of embodiment of a transmitter is shown, (a) is cross-sectional explanatory
drawing, (b) is perspective explanatory drawing.
It is cross-sectional explanatory drawing which shows the other example of embodiment of a
transmitter.
It is perspective explanatory drawing which shows the external appearance of a handset.
It is cross-sectional explanatory drawing which shows the structure of the conventional
transmitter.
It is a graph which shows the sensitivity with respect to the frequency in a transmitter.
It is cross-sectional explanatory drawing which shows the structure of the conventional
transmitter.
[0024]
Hereinafter, an example of embodiment of the transmitter of this invention is demonstrated,
referring FIG.1 and FIG.11.
The transmitter 2 is integrally mounted on the main body of the handset 1 of the telephone as
shown in FIG.
FIG. 1 shows a part of the transmission side of the handset 1 constituting the transmitter 2. FIG.
1 (a) is a schematic sectional view, and FIG. 1 (b) is a plan view.
[0025]
The transmitter 2 has a microphone unit (microphone) 11 mounted on the microphone mounting
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plate 10, a front air chamber 12 positioned on the front side of the microphone unit 11, and a
front air chamber 12 with respect to the microphone unit 11. The mouthpiece wall 13 is
provided at the opposite position.
The mouthpiece wall 13 is formed at the end of the body 1a on the transmitter side of the
handset 1. The peripheral wall 14 is extended from the mouthpiece wall 13 to the inner portion
of the body 1a. The microphone mounting plate 10 is mounted.
The space of the front air chamber 12 disposed between the microphone mounting plate 10 and
the mouthpiece wall portion 13 has a peripheral shape of a truncated cone formed on the
mouthpiece wall portion 13 with an inner wall 13a and a peripheral shape of the truncated cone
The microphone unit 11 mounted on the microphone mounting plate 10 is disposed so as to be
divided by the peripheral wall 14 having the inner wall 14a, and to face the space of the front air
chamber 12 so as to face the mouthpiece wall portion 13.
A signal line is connected to the microphone unit 11, and an audio signal is output to a circuit
(not shown).
[0026]
In addition, an inner wall 13a of the frusto-conical circumferential shape formed on the
mouthpiece wall 13 (the shape of a first truncated cone) and an inner wall 14a of a frusto-conical
circumferential shape formed on the peripheral wall 14 (a second truncated cone) In the space of
the front air chamber 12, the distance between the inner walls 13a and 14a is the same, and the
outer diameter and the inner diameter increase from the microphone unit 11 side to the
mouthpiece wall 13 side. It consists of continuous annular zone space.
[0027]
In the mouthpiece wall portion 13, a plurality of sound holes 15 communicating with the space
of the front air chamber 12 are annularly formed along a circle (see FIG. 1 (b)) around the
outermost end of the front air chamber 12. It is configured to be placed.
[0028]
According to the transmitter 2 of the above-mentioned structure, the sound wave from the
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outside passes through the sound hole 15 provided in the mouthpiece wall 13 and receives the
sound of the microphone unit 11 through the space of the front air chamber 12 Led to the
surface.
The space of the front air chamber 12 is defined by the inner wall 13a of the frusto-conical
circumferential shape formed in the mouthpiece wall portion 13 and the inner wall 14a of the
frusto-conical circumferential shape formed in the peripheral wall 14 If the frusto-conical
peripheral shape of 14a is the same, the volume of the volume of the frusto-conical shape
decreases by forming the inner wall 13a in the mouthpiece wall 13 as compared with the space
of the front air chamber 22 of FIG. While the number of sound holes 15 decreases.
[0029]
Hereinafter, in the structure of the microphone of FIG. 1, the influence on the broadening due to
the volume of the front air chamber 12 becoming smaller by the volume of the truncated cone
shape compared to the structure of the front air chamber 22 of FIG. The influence of the
reduction in the total number of cross-sectional areas due to the reduction in the number of
sound holes 15 and the broadening of the bandwidth will be discussed with reference to FIG.
The volume to be reduced from the front air chamber 12 is similar to that of the front air
chamber 12 as shown by a dotted line, and the front air chamber and the reduction volume are
conically calculated to simplify the calculation of the volume. In FIG. 2, the diameter of the
second conical shape (corresponding to the shape of the second truncated cone in FIG. 1)
including the inner wall 14a is φD and the height is j, and the first conical shape including the
inner wall 13a (FIG. 1) Corresponding to the shape of the first truncated cone) with φE and
height k, and electrostatic distance (the shortest distance between the top of the first cone and
the bottom of the second cone) is j0 .
[0030]
Since the first conical shape and the second conical shape are similar, the following equation is
established between the height k of the first conical shape and the height j of the second conical
shape . k = j × E / D Then, the electrostatic distance j0 is j0 = √ (j <2> + E <2> / 4). Further, j can
be expressed by the following equation: j = √ (j0 <2> -E <2> / 4).
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[0031]
The electrostatic distance in the front air chamber 22 of FIG. 14 is j because it is equal to the
height of the second conical shape, and the electrostatic distance j0 in the front air chamber 12
of FIG. 1 is larger than j. With respect to protection from static electricity, the structure shown in
FIG.
[0032]
Next, the area where the sound hole can be opened in the front air chamber 12 of FIG. 1 is: Sm =
(π / 4) (D <2> -E <2>).
The volume obtained by subtracting the volume of the first conical shape is: VF = (π / 12) (D <2>
× j−E <2> × k) = (π / 12) (D <2> × j−E <2> × j × E / D) = (πj / 12D) (D <3> −E <3>) = (π /
12D) (D <3> −E <3>) √ (j0 <2>) It becomes -E <2> / 4).
[0033]
Since the high frequency is obtained by the above-mentioned equation (A) by fH = (α / 2π) √
(Sm / VF), the high frequency fH1 of the transmitter corresponding to FIG. 1 substitutes Sm and
VF. Then, fH 1 = (α / 2π) √ {(π / 4) (D <2> −E <2>) / (π / 12D) (D <3> −E <3>) √ (j0 <2>) It
becomes -E <2> / 4)}. The high frequency fH0 in the case of the front air chamber 22 of FIG. 13
is fH0 = (α / 2π) π {(π × D <2> / 4) / (π × D <2> × j0 / 12)} = It becomes ((alpha) / 2 (pi)
(root) (3 / j0).
[0034]
The ratio (fH / fH0) between the high frequency fH and the high frequency fH0 is given by
equation 1.
[0035]
[0036]
Here, when D = 20 mm and j0 = 10 mm, the ratio (fH / fH0) of the high frequency fH to the high
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frequency fH0 is expressed by Equation 2.
[0037]
[0038]
When the ratio of the high frequency fH to the high frequency fH0 when the diameter E of the
first conical shape was changed from 0 to 18 mm was calculated in Equation 2, the graph shown
by the solid line in FIG. 3 was obtained. .
According to this graph, the higher frequency is increased when the diameter D of the conical
shape (first conical shape) including the inner wall 13a is made closer to the diameter D of the
conical shape (second conical shape) including the inner wall 14a. In particular, when the
diameter E of the first conical shape is 18 mm, it can be confirmed that the value of the high
frequency becomes about 1.3 times.
[0039]
That is, according to the above-described structure of the transmitter 2 (FIG. 1), a truncated cone
shape similar in shape to the space of the front air chamber to the structure of the conventional
transmitter 2 (FIG. 14) Then, the distance between the mouthpiece wall portion 13 and the
microphone unit 11 is maintained (if the size of the peripheral wall 14 is the same, the
electrostatic distance j in FIG. 1 can be made longer than the electrostatic distance j0 in FIG. The
capacity of the front air chamber 12 can be reduced.
In this case, the sum of the number of sound holes and the total area of the cross-sectional area
is reduced, and there is a concern that the effect is small. As the influence of the other is larger, it
is possible to realize wide band as a whole.
[0040]
FIG. 4 shows another example of the embodiment of the transmitter. Components having the
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same functions as those of FIG. 1 are assigned the same reference numerals and explanations
thereof will be omitted.
In the example of the transmitter of FIG. 4, similar to the conical shape of the inner wall 13a and
the inner wall 14a on the outer side (the sound hole forming side) of the mouthpiece wall 13
with respect to the transmitter of FIG. Forming a conical recess 16 having a surface that
By providing the conical recess 16 in the mouthpiece wall portion 13, the thickness of the
mouthpiece wall portion 13 constituting the main body 1a of the handset 1 can be made
constant, and the occurrence of cracking and the like can be prevented and durability is
achieved. While improving the quality, the appearance of the transmitter 2 can be made a novel
design.
[0041]
FIG. 5 shows another example of the embodiment of the transmitter. Components having the
same functions as those of FIG. 1 are assigned the same reference numerals and explanation
thereof is omitted. In the example of the transmitter of FIG. 5, the case where the outer surface
13b of the mouthpiece wall 13 and the microphone attachment plate 10 are not parallel to each
other and the outer surface 13b is inclined is shown. According to this example, the volume of
the front air chamber 12 is reduced with respect to the mouthpiece wall portion 13 having the
inclined outer surface 13 b by projecting a truncated cone having an inclined bottom surface into
the space of the front air chamber. To realize a wide band of the transmitter 1.
[0042]
FIG. 6 shows another example of the embodiment of the transmitter. Components having the
same functions as those in FIG. 1 are assigned the same reference numerals and explanation
thereof is omitted. Although the first conical shape including the inner wall 13a and the second
conical shape including the inner wall 14a are formed to have similar shapes in the microphones
of the respective examples described above, in the example of FIG. This is the case where the
shape and the second conical shape are not similar. That is, the inclination of the first conical
inner wall 13a is configured to be steep relative to the second conical inner wall 14a. Even in this
case, the volume of the front air chamber 12 can be reduced as compared with the structure of
FIG. Further, in this case, since the area for forming the sound holes 15 can be enlarged
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compared to FIG. 1, the sound holes 15 are arranged in two rows along the annular circle of the
end portion of the front air chamber 12 in the mouthpiece wall portion 13 It is arranged and
formed.
[0043]
Hereinafter, in the structure of the transmitter of FIG. 6, the influence on the broadening due to
the volume of the front air chamber 12 becoming smaller by the volume of the truncated cone
shape compared to the structure of the front air chamber 22 of FIG. The influence of the
reduction in the total number of cross-sectional areas due to the reduction in the number of
sound holes 15 and the broadening of the bandwidth will be discussed with reference to FIG. The
volume (conical shape) to be reduced from the front air chamber 12 has its apex position fixed as
shown by the dotted line. Also, in order to simplify the calculation of volume, the front air
chamber and the volume to be reduced are calculated conically. In FIG. 7, the diameter of the
conical shape (second conical shape) including the inner wall 14a is φD, the height is j, and the
diameter of the conical shape (first conical shape) including the inner wall 13a is φE, the height
k And the electrostatic distance (the shortest distance between the apex of the second conical
shape and the periphery of the bottom of the first conical shape) is j0.
[0044]
As for the first conical shape and the second conical shape, it is assumed that the shape of the
first conical shape changes with the apex position as a constant position. Since the vertex
position of the first conical shape to be changed is a fixed position between the height j of the
second conical shape and the height k of the first conical shape, for example, it is assumed that
the following equation holds Do. k = j-1 Then, the electrostatic distance j0 is j0 = √ (j <2> + E <2>
/ 4). Further, j can be expressed by the following equation: j = √ (j0 <2> -E <2> / 4).
[0045]
The electrostatic distance in the front air chamber 22 of FIG. 14 is j because it is equal to the
height of the second conical shape, and the electrostatic distance j0 in the front air chamber 12
of FIG. 6 is a value larger than j. With regard to protection from static electricity, the structure
shown in FIG.
[0046]
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13
Next, the area where the sound hole can be opened in the front air chamber 12 of FIG. 6 is: Sm =
(π / 4) (D <2> -E <2>).
The volume obtained by subtracting the volume of the first conical shape is: VF = (π / 12) (D <2>
× j−E <2> × k) = (π / 12) {D <2> × j−E <2> × (j−1)} = (π / 12) {(D <2> × √ (j0 <2> −E
<2> / 4) −E <2> × √ (j0 <2> −) It becomes E <2> / 4) + E <2>}.
[0047]
Since the high frequency is obtained by the above-mentioned equation (A) by fH = (α / 2π) √
(Sm / VF), the high frequency fH1 of the transmitter corresponding to FIG. 6 substitutes Sm and
VF. Then, fH1 = (α / 2π) √ {π (D <2> -E <2>) / 4} × √ [12 / π {D <2> √ (j0 <2> -E <2> / 4) ) E <2> √ (j0 <2> -E <2> / 4) + E <2>}]. The high frequency fH0 in the case of the front air
chamber 22 in FIG. 14 is fH0 = (α / 2π) √ {(π × D <2> / 4) / (π × D <2> × j0 / 12)} = It
becomes ((alpha) / 2 (pi) (root) (3 / j0).
[0048]
The ratio (fH / fH0) of the high frequency fH to the high frequency fH0 is given by Equation 3.
[0049]
[0050]
Here, when D = 20 mm and j0 = 10 mm, the ratio (fH / fH0) of the high frequency fH to the high
frequency fH0 is as shown in Expression 4.
[0051]
[0052]
When the ratio of the high frequency fH to the high frequency fH0 when the diameter E of the
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first conical shape was changed from 0 to 18 mm was calculated in Equation 4, the graph shown
by the dotted line in FIG. 3 was obtained. .
According to this graph, when the diameter E of the conical (first conical) including the inner wall
13a is smaller than the diameter D of the conical (second conical) including the inner wall 14a,
several 2 (FIG. 1) The structure of FIG. 1 is more effective in the case where the diameter E
approaches D, although the high frequency tends to increase to about 1.1 times than the
structure of FIG.
[0053]
That is, according to the above-described structure of the transmitter 2 (FIG. 6), a frusto-conical
shape not similar in shape to the space of the front air chamber is projected with respect to the
structure of the conventional transmitter 2 (FIG. 14). 6 by maintaining the distance between the
mouthpiece wall portion 13 and the microphone unit 11 (if the size of the peripheral wall 14 is
the same, the electrostatic distance j in FIG. 6 can be made longer than the electrostatic distance
j0 in FIG. The capacity of the front air chamber 12 can be reduced.
In this case, the sum of the number of sound holes and the total area of the cross-sectional area
is reduced, and there is a concern that the effect is small. As the influence of the other is larger, it
is possible to realize wide band as a whole.
[0054]
FIG. 8 shows another example of the embodiment of the transmitter. Components having the
same functions as those of FIG. 1 are assigned the same reference numerals and explanations
thereof will be omitted.
The plan view of the transmitter of FIG. 8 is the same as that of FIG. 1 (b).
In the example of the transmitter shown in FIG. 8, the space of the front air chamber 17 disposed
between the microphone mounting plate 10 and the mouthpiece wall 13 is cylindrical, and the
end of the circle of the front air chamber 17 is at the end. A plurality of sound holes 15 are
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formed in the mouthpiece wall portion 13 along the same. According to this example, since the
sound hole 15 is formed in the mouthpiece wall 13 along the peripheral end of the front air
chamber 17, the electrostatic distance L can be secured and the thin front air can be secured. By
using the chamber 17, the volume can be minimized without forming a bulging portion in the
front air chamber, and the broadband of the transmitter 2 can be realized.
[0055]
FIG. 9 shows another example of the embodiment of the transmitter, which is a further
development of the concept of FIG. 8 in which a thin front air chamber is adopted. That is, at the
end of the main body 1 a of the handset 1, the disk-like microphone mounting plate 10 provided
with the microphone unit 11 at the center is fixed. In the microphone mounting plate 10, a
plurality of disk-like mouthpiece wall portions 13 parallel to the microphone mounting plate 10
with a gap are provided around the microphone mounting plate 10 and the mouthpiece wall
portion 13. It is mounted via the connecting portion 18. With the above-described structure, the
space between the mouthpiece wall portion 13 and the microphone attachment plate 10
constitutes the front air chamber 17, and the connecting portion 18 constitutes the sound hole
25. According to this example, since the sound holes 25 are located around the front air chamber
17, the electrostatic distance L can be secured, and by making the thin front air chamber 17, the
front air chamber can be made to the front air chamber. The volume can be minimized without
forming the bulging portion, and the broadband of the transmitter 2 can be realized.
[0056]
FIG. 10 shows another example of the embodiment of the transmitter. Components having the
same functions as those in FIG. 9 are assigned the same reference numerals and explanation
thereof is omitted. That is, instead of the plurality of connecting portions 18 provided around the
microphone attachment plate 10 and the mouthpiece wall portion 13, a plurality of supports 19
are provided between the microphone attachment plate 10 and the mouthpiece wall portion 13.
Thus, the front air chamber 17 is formed between the microphone attachment plate 10 and the
mouthpiece wall 13. In the case of this example, all around the space sandwiched by the
microphone attachment plate 10 and the mouthpiece wall portion 13 constitute the annular
sound hole 26, so the area of the sound hole is enlarged to achieve a wide band. Can.
[0057]
Reference Signs List 1 handset, 2 transmitter, 10 microphone mounting plate, 11 microphone
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unit, 12 front air chamber, 13 mouthpiece wall, 13a inner wall, 13b outer surface 14
circumferential wall 14a Inner wall, 15 sound hole, 16 conical recess, 17 front air chamber, 18
connection part, 19 support body, 25 sound hole, 26 annular sound hole.
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