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JPH1127781

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JPH1127781
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
sound pressure microphone used for an acoustic intensity probe to which a two microphone
method is applied.
[0002]
2. Description of the Related Art In an acoustic intensity probe to which the two-microphone
method is applied, a difference in phase characteristics particularly in a low frequency region
between two microphones greatly affects the measurement accuracy of acoustic intensity. For
this reason, when manufacturing an acoustic intensity probe, the processing accuracy of each
microphone is increased to make the phase characteristics uniform, or a large number of
microphones are manufactured, and two microphones having the phase characteristics uniform
are selected from among them. There is.
[0003]
As a conventional condenser type sound pressure microphone, as shown in FIG. 5, in order to
keep the static pressure inside and outside of the diaphragm 100 equal so that the correct sound
pressure can be obtained even if the atmospheric pressure fluctuates, the inside of the
microphone is A very thin pressure balance passage 103 for ventilating the back electrode
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portion space 101 and the outside (outside) is formed in the insulator 104 serving as a partition
wall. Reference numeral 105 denotes a back electrode, 106 denotes an output terminal, and 107
denotes an outer peripheral wall.
[0004]
However, since the pressure balance passage 103 is very thin and the viscous resistance of air is
large and acts as an acoustic resistance, in the case of a high frequency, the pressure balance
passage 103 passes through the pressure balance passage 103 and the inside of the vibrating
membrane 100. Affect the inside of the vibrating membrane 100 at low frequencies. Therefore,
in the case of measuring the sound pressure, by providing the pressure balance passage 103, in
addition to the sound pressure applied to the vibrating film 100 directly from the outside of the
vibrating film 100, the vibrating film 100 also flows from the inside of the vibrating film 100
through the pressure balance passage 103. The sound pressure is applied to the sound source,
causing the phase characteristics to be disturbed.
[0005]
Therefore, the influence of the frequency range is determined by the shape of the pressure
balance passage 103. Therefore, in order to reduce the phase characteristic difference between
the microphones, the pressure balance passages 103 of the paired microphones have the same
shape. It is necessary to reduce the variation in machining accuracy so that However, in the case
of low frequency, it is not easy to process the pressure balance passage 103 to the extent that
the desired phase characteristic is satisfied because it requires high processing accuracy, and the
pressure balance passage is made the same shape for paired microphones. It is difficult to
process 103.
[0006]
The present invention has been made in view of such problems in the prior art, and the objective
of the present invention is that the variation of the phase characteristic of the low frequency of
the microphone is small, and special processing accuracy is required. It is an attempt to propose
a sound pressure microphone that does not
[0007]
SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present
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invention ventilates a back electrode space and the outside through an acoustic resistor.
[0008]
The acoustic resistor can be formed of a porous sintered metal.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be
described below with reference to the attached drawings.
Here, FIG. 1 is a schematic sectional view of the sound pressure microphone according to the
present invention, FIG. 2 is a sectional view showing the attached state of the sintered metal
body, FIG. 3 is an exploded perspective view of a female member of the output terminal, and FIG.
It is sectional drawing which shows the other attachment state of a sintered metal body.
[0010]
The sound pressure microphone according to the present invention is, as shown in FIG. 1, a
condenser type microphone, in which a vibrating membrane 2 is attached to the open end of a
cylindrical outer peripheral wall 1 and a back electrode is opposed to this vibrating membrane 2
3 is disposed in the outer peripheral wall 1, the output terminal 4 is connected to the back pole
3, and an insulator 6 provided with a through hole 6 a at the center as a partition to form the
back pole portion space 5 is attached to the outer peripheral wall 1 Further, the gap 7 formed by
the through hole 6a of the insulator 6 and the output terminal 4 loosely mounted to the through
hole 6a is closed by the sintered metal body 8 as an acoustic resistor.
[0011]
The sintered metal body 8 has a cylindrical shape and has a through hole 8a formed in the axial
center thereof, and the output terminal 4 is fitted in the through hole 8a, and abuts against the
insulator 6 to close the gap 7.
The illustration is omitted for a bias DC voltage source connected to the output terminal 4 and
the like, and a case body connected to the outer peripheral wall 1 and the like.
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[0012]
The sintered metal body 8 is a porous member having a large number of continuous vents in
place of the pressure balance passage 103 used in the conventional sound pressure microphone
in order to ventilate the back electrode portion space 5 and the outside world. It is.
For the sintered metal body 8, metal powder such as stainless steel powder or bronze powder is
used as a raw material powder.
[0013]
And although the size and shape of each of the large number of vent holes in the sintered metal
body 8 are different from each other, the viscosity resistance of the average air when the entire
sintered metal body 8 is considered as a pressure balance passage is plural Between the sintered
metal bodies 8 of the above.
[0014]
As a result, the variation of the phase characteristic of the low frequency of the sound pressure
microphone is reduced.
Also, no holes or grooves are required as pressure balancing passages, and no special processing
accuracy is required.
[0015]
Further, as the acoustic resistor, a ceramic sintered member having the same structure as that of
the sintered metal body 8, a polymer material, a sheet of a tetrafluorinated ethylene continuous
porous body, or the like may be used.
[0016]
As a method of attaching the sintered metal body 8, as shown in FIG. 2, the male member 4a of
the output terminal 4 integrally formed with the back electrode 3 is inserted into the through
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hole 8a of the sintered metal body 8, and then the male member 4a is screwed into the female
member 4b of the output terminal 4, and the sintered metal body 8 is sandwiched between the
locking portion 4c formed on the outer periphery of the male member 4a and the insulator 6.
[0017]
The female member 4b of the output terminal 4 is fixed in contact with the insulator 6 by
screwing the male member 4a.
The outer diameter of the sintered metal body 8 is larger than the inner diameter of the through
hole 6 a of the insulator 6.
[0018]
Further, as shown in FIG. 3, the female member 4b is formed with a through hole 4d and a fitting
member 4e which is fitted from below to the through hole 6a of the insulator 6, and a pressing
ring 4g in which the through hole 4f is formed. And the terminal member 4i of the blind tube
which screwed to the internal peripheral surface of 4 h of through holes.
[0019]
By screwing the male member 4a of the output terminal 4 into the female member 4b of the
output terminal 4, the sintered metal body 8 closes the gap 7 to function as a pressure balance
passage between the back electrode portion space 5 and the outside world. The back electrode 3
to the female member 4b can be electrically connected.
[0020]
As described above, since the sintered metal body 8 is fixed by being sandwiched between the
locking portion 4 c and the insulator 6, no adhesive is required, and the air hole of the sintered
metal body 8 is not blocked by the adhesive. It is possible to prevent the occurrence of variations
in the acoustic resistance of the sintered metal body 8.
[0021]
Further, as another method of attaching the sintered metal body, as shown in FIG. 4, a cylindrical
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output terminal 10 is formed integrally with the back electrode 3, and a cylindrical sintered body
is formed in the hollow portion 11 of the output terminal 10. After fitting the sintered metal body
12, the output terminal 10 can be inserted into the through hole 6 a of the insulator 6.
Reference numeral 13 denotes an electrode screwed to the tip of the output terminal 10.
[0022]
The wall 10a of the output terminal 10 has a plurality of through holes 10b for communicating
the back electrode portion space 5 with the hollow portion 11, a step 10c for positioning the
sintered metal body 12 in contact with the hollow portion 11, and the outer space A plurality of
communicating through holes 10d are formed.
[0023]
The cylindrical sintered metal body 12 is formed by sintering at a predetermined temperature in
a state in which metal particles are filled inside a metal cylindrical member.
In addition, when the sintered metal body 12 is fitted into the hollow portion 11 of the output
terminal 10, an unnecessary gap can not be formed between the outer peripheral surface of the
sintered metal body 12 and the inner peripheral surface of the output terminal 10. The part is
sealed with an adhesive or the like.
[0024]
By inserting the output terminal 10 into which the sintered metal body 12 is fitted as described
above into the through hole 6 a of the insulator 6, the through hole 10 b, the hollow portion 11,
and the like between the back electrode portion space 5 and the outside. Desired ventilation is
maintained through the sintered metal body 12, the hollow portion 11 and the through hole 10d.
[0025]
According to the mounting method of the sintered metal body 12 shown in FIG. 4, compared with
the mounting method of the sintered metal body 8 shown in FIG.
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[0026]
As described above, according to the present invention, by ventilating the back electrode portion
space and the outside through the acoustic resistor, it becomes a substitute for the pressure
balance passage, and no special processing accuracy is required. The variation in phase
characteristics of the low frequency region of the microphone can be reduced.
[0027]
Further, by using a sintered metal body having a large number of continuous vents as the
acoustic resistor, it is possible to further reduce the dispersion of the phase characteristics in the
low frequency region of the microphone.
[0028]
Brief description of the drawings
[0029]
1 is a schematic sectional view of a sound pressure microphone according to the present
invention
[0030]
Fig. 2 Cross section showing the attached state of the sintered metal body
[0031]
Fig. 3 An exploded perspective view of the female member of the output terminal
[0032]
Fig. 4 A sectional view showing another mounting state of the sintered metal body
[0033]
Fig. 5 A schematic cross-sectional view of a conventional sound pressure microphone
[0034]
Explanation of sign
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[0035]
DESCRIPTION OF SYMBOLS 1 ... Outer peripheral wall, 2 ... Vibrating film, 3 ... Back pole, 4, 10 ...
Output terminal, 5 ... Back pole space, 6 ... Insulator, 7 ... Gap, 8, 12 ... Sintered metal body
(Acoustic resistor ).
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