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FIELD OF THE INVENTION The present invention relates to a throat microphone that is resistant
to howling. 2. Related Art Conventionally, as throat microphones of this type, microphones of an
electrodynamic type, an electret condenser type, a bone conduction type, and the like have been
adopted and commercialized. Here, the electret capacitor type is described as an example. FIG. 5
shows a cross-sectional view of a conventional electret condenser type throat microphone. In FIG.
5, 1 is a cylindrical metal case having a sound hole 1a on the top surface, and 2 is a metal ring to
which a vibrating film 3 (electret material) formed by applying metal deposition 3a on one side is
attached and fixed. , 4 is a gap spacer, 5 is a fixed electrode having a damping hole 5a, 6 is an
insulator, 7 is an FET for impedance conversion, 7a is an input terminal of the FET 7 and is
electrically connected to the fixed electrode 5 by contact or spot welding Connected. Reference
numeral 8 denotes a printed circuit board, to which the output terminal 7b of the FET 7 is
connected and fixed by soldering 8a or the like. Each of these parts is inserted into the case 1
and its end is fixed to the circumference of the printed circuit board 8 by caulking portion 1b or
the like. 9 is a code for taking out the output, and 10 is a metal case 1. 11 is an arm, 12 is a
dustproof picture cloth, and 13 is a skin (throat). FIG. 6 shows an example of use of this throat
microphone attachment 7. The operation of the above embodiment will now be described. In FIG.
5, there is an air layer between the vibrating membrane 3 and the fixed electrode 5 and exhibits
a capacitor (capacitance) Co of about several PF to several 10 PF. This Co is slightly changed by
the vibration of the skin 13 due to the voice and the vibration of the vibrating membrane 3 due
to the air transmission. Assuming that this change in capacitance is eighty, the capacitance of the
capacitor is C 0 v = Co ± 80. Therefore, it can be electrically taken out through the voltage
change ΔV = Eo ·. る。 (K = proportional coefficient, S = equivalent effective area of vibrating
membrane 3, g = equivalent gap of vibrating membrane 3 and fixed electrode 5, Eo = surface
potential of electret material) and sensitivity K. Depends on the stray capacitance Cs, the gain Gy
of the FET 7 and the like. FIG. 7 shows an equivalent circuit diagram of this prior art example. In
the prior art, although the type using the electret material for the vibrating membrane 3 is
shown, there is also a type in which the electret material is attached to the fixed electrode 5 by
any method. Further, the printed board 8 is for taking out the output of the FWT 7 and is not
required to be separately a printed board, and there is a method for taking out the output
terminal 7b of the FET 7 as it is, a method for taking out via the metal terminal plate etc.
The FET 7 can obtain the same function regardless of whether it is configured internally or
externally. SUMMARY OF THE INVENTION However, in the above-described conventional
example, when there is a gap or the like between the case and the skin because of the
configuration in which the skin digging is transmitted to the vibrating membrane by air
transmission and the output is taken out by this vibration. Depending on the voice, it may cause
howling. In addition, there is also the problem that the deterioration is thick in terms of sound
quality. The present invention solves such conventional problems, and it is an object of the
present invention to provide a throat microphone that is difficult to howl and has less
deterioration in sound quality. Means for Solving the Problems In order to achieve the above
object, the present invention electretizes a metal fixed electrode in which a polymer film is fixed
by heat fusion or the like in a cylindrical metal case having a hole in a top surface, and insulation.
While holding by the body, it is connected to the input terminal of FgT, the output terminal is
taken out through the printed circuit board, and the metal case and the skin are electrically
conducted. Operation The present invention has the following operation by the above
configuration. That is, a capacitor is formed between the skin and the metal fixed electrode, and a
change in skin vibration can be grasped by a change in capacitance, converted into an electric
signal by the built-in FgT, and taken out. Embodiment 1 FIG. 1 shows the configuration of an
embodiment of the present invention. The same parts as in FIG. 5 are indicated by the same
numbers. In FIG. 1, 21 denotes a cylindrical metal case having a hole 21a, 25 denotes a metal
fixed electrode on which the polymer film 25b is attached by heat fusion or an adhesive or the
like and fixed, and 25a denotes a braking hole. The insulator 6, the FET 7, and the printed board
8 are the same as in the prior art, and these four internal components are inserted into the metal
case 21, and the end of the metal case 21 is fixed by caulking the portion of the printed board 8
by caulking portion 21b or the like. ing. The reference numeral 30 denotes a case of the metal
case 21 and the reference numeral 34 denotes a metal plate, which are electrically conducted to
the metal case 21. It is not necessary to provide this metal plate 34 as long as the metal case 21
directly contacts the skin 13. In the above configuration, the polymer film 25b is electretized by
any method. Therefore, an FEP film or the like is suitable as the material of the polymer film 25b.
FIG. 2 shows the aerobic equivalent circuit of FIG. 1, and a capacitor Co + is formed between the
skin 13 and the metal fixed electrode 25. The skin 13 is not a perfect conductive object but has a
certain degree of conductivity, so it may be considered as a circuit in the same figure.
As the skin 13 vibrates due to vocalization, the capacitor Co! Causes a capacity change.
Therefore, as in the conventional case, it can be taken out as a voltage change. As described
above, according to the above embodiment, conventionally, the vibration of the skin 13 is
vibrated by air transmission to vibrate the vibrating membrane 3. That is, although the indirect
change was caught, according to the present invention, the change of the skin 13 is directly
taken as the capacitance change, and this capacitance change is used as the electret's charge
(surface potential) to produce a sensitive electrical signal. Has the effect of taking out. In the
above embodiment, since the skin 13 is not completely conductive, it has the disadvantage of
being more susceptible to inductive noise (such as ham) than the hole 21a, but a method of
removing or reducing it by a filter by an electric circuit is also conceivable. Alternatively, two
microphones may be connected in parallel, one for detecting vibration and the other for
induction noise cancellation. FIG. 3 (al is a general use example of a throat microphone, in which
the output of the microphone is taken out via an equalizer. That is, it is effective in correcting
transmission loss by the skin 13 and reproducing more faithfully. The same figure (bl is an
example which shows the frequency-gain characteristic of an equalizer. FIG. 4 is a cross sectional
view showing another embodiment. This is because the electret is deteriorated by the adhesion of
moisture, dust and the like, so that a thin film protective film 35 for drip-proof etc. is formed on
the front side of the metal fixed electrode 25. In this embodiment, the metal ring 36 is adhesively
fixed to the metal ring 36 in any way, and is formed on the front surface of the metal fixed
electrode 25 with a gap as a spacer 37. As the conductive fMiTI film 35, a conductive one forms
an electret condenser microphone and operates abnormally, so a film having a high insulating
property is desirable. As described above, various methods can be considered other than the
configuration side of the protective film 35 provided for the purpose of preventing the
deterioration of the electret. For example, the spacer 37 is abolished, and the protective film 35
and the metal ring 36 are configured reversely to that shown in FIG. Although not shown in this
embodiment, in the mounting, the microphone of the present invention is formed at both ends of
the arm 11, and a configuration in which two sums are taken can be considered. It is. Although
the throat microphone of the present invention has been described above, various applications
such as heart sound detection and a sphygmomanometer can be considered from the viewpoint
of directly capturing the vibration of the skin 13. As is apparent from the above embodiments,
the present invention directly recognizes the change in skin vibration as the change in
capacitance of the capacitor, that is, since the vibration of the vibration source itself can be
directly converted into an electrical signal, the sound quality is less deteriorated and faithful.
Since the speaker can be widely sounded and does not have a vibrating membrane as in the prior
art, the mounting has an effect that it is difficult to cause howling even when there is a space
between the part and the skin.
Also, there is an advantage that it is difficult to spread this against ambient noise.
Brief description of the drawings
1 is a cross-sectional view of a throat microphone showing one embodiment of the present
invention, FIG. 2 is an electrical etc. in FIG. 1, FIG. 4 is a cross-sectional view showing another
embodiment of the present invention, and FIG. 6 is a mounting view of the throat microphone,
and FIG. 7 is an electrical equivalent circuit diagram in FIG.
21 · Metal case 25 · · · Metal fixed electrode 25b · · · Polymer film, 6 · · · · · · · · · · · · · · · · · · · · · · · 7
printed circuit board, 30 · · · installation Is a case, 34 .. metal plate, 9: cord for taking out the
output, 11: arm, 13: skin. Name of Agent Attorney Shigetaka Ogino has 1 person Fig. 2 Fig. 3 /
third cause Fig. 70-WM
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