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DESCRIPTION JP2005252575

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DESCRIPTION JP2005252575
PROBLEM TO BE SOLVED: To provide a microphone covering structure and a wind tunnel test
device capable of measuring wind noise and the like and measuring aerodynamic noise and the
like generated from a test object with high accuracy. SOLUTION: A thin film portion 7 is fixed to
substantially the same surface as a wall surface of a fixed wall portion 3a with a gap from a
vibrating surface 5d. The thin film portion 7 is formed by laminating and bonding a plurality of
thin films 8 and 9 and the thin films 8 and 9 are synthetic resin adhesive tapes made of a
polypropylene film or the like. The adhesive layer 9 b of the thin film 9 is attached to the wall
surface of the fixed wall portion 3 a, and the vibrating surface 5 d is covered by the thin film
portion 7. Therefore, when the air flows in the wind tunnel measurement unit 3, the thin film
portion 7 prevents the air flow in the vicinity of the vibration surface 5d from being disturbed,
and the air flowing in the wind tunnel measurement unit 3 is directly on the vibration surface 5d.
The thin film part 7 prevents the hitting. As a result, noise such as wind noise and wind noise
generated by air passing near the vibrating surface 5 d is suppressed. [Selected figure] Figure 4
Microphone covering structure and wind tunnel test device
[0001]
The present invention covers the coating structure of a microphone that covers the vibrating
surface of the microphone with a thin film portion, and the wind tunnel that measures the
behavior of the test object generated by the flow of the gas when the gas flows through the test
object in the wind tunnel. It relates to a test apparatus.
[0002]
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1
The conventional wind tunnel test apparatus includes a wind tunnel measurement unit for
installing a test object, an outlet for blowing air to the wind tunnel measurement unit, a suction
port for sucking air from the wind tunnel measurement unit, and a test target disposed in the
wind tunnel measurement unit. The microphone etc. which measure the noise which generate |
occur | produces from a thing are provided (for example, refer patent document 1).
This conventional wind tunnel test apparatus is an open-drum type wind tunnel test apparatus in
which the wind tunnel measurement portion between the air outlet and the air inlet is open, and
when the air flow is applied to the test object, the test object Noise such as aerodynamic noise
generated from objects is measured by the microphone. In such a conventional wind tunnel test
apparatus, the microphone is disposed at a position away from the air flow so that the air flow
does not directly hit the microphone.
[0003]
Japanese Patent Publication No. 2000-507360
[0004]
On the other hand, in the conventional wind tunnel test apparatus, there is a closed cylinder type
wind tunnel test apparatus in which a wind tunnel measurement unit is surrounded by a shell
and a flow path constitutes a closed circuit.
In such a closed cylinder type wind tunnel test apparatus, when a microphone is disposed in the
wind tunnel measurement unit as in the open cylinder type wind tunnel test apparatus, the flow
of air directly strikes the microphone makes accurate measurement difficult. For this reason, in
the closed-loop wind tunnel test apparatus, a recess is formed in the fixed wall portion of the
wind tunnel measurement unit, and the microphone is installed in this recess so that the tip
surface of the microphone and the wall surface of the fixed wall are substantially the same
surface. doing. For example, the microphone is installed so that the end surface of the protective
cap that protects the vibrating surface of the microphone is substantially flush with the wall
surface of the fixed wall, or the end surface of the urethane cover that covers this protective cap.
A microphone is installed so as to be substantially flush with the wall surface of the fixed wall
portion.
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2
[0005]
In the conventional closed-loop wind tunnel test apparatus, since a large number of through
grooves are formed on the tip end surface of the protective cap portion, there is an uneven
portion on the tip end surface of the protective cap portion. There is a minute uneven portion.
Therefore, when the air flow hits these irregularities, the air flow is disturbed, and the air flow
directly strikes the vibrating surface of the microphone by passing through the through groove
of the protective cap, causing wind noise and noise. The noise component by wind noise etc.
becomes large. As a result, there has been a problem that aerodynamic noise and the like
generated from the test object can not be measured with high accuracy by the microphone.
[0006]
An object of the present invention is to provide a coating structure of a microphone and a wind
tunnel test apparatus capable of reducing wind noise and measuring aerodynamic noise and the
like generated from a test object with high accuracy.
[0007]
The present invention solves the above problems by means of solutions as described below.
In addition, although the code | symbol corresponding to embodiment of this invention is
attached | subjected and demonstrated, it does not limit to this embodiment. The invention
according to claim 1 is a coating structure of a microphone in which the vibrating surface (5d) of
the microphone (5) is covered with the thin film portion (7; 10), and the vibrating surface is a
wall surface of the fixed wall portion In the microphone covering structure (6), the thin film
portion is disposed in substantially the same plane as the wall surface of the fixed wall portion.
[0008]
A second aspect of the present invention is the microphone covering structure according to the
first aspect, wherein the thin film portion is fixed to a wall surface of the fixed wall portion.
[0009]
The third aspect of the invention is the microphone covering structure according to the first or
second aspect, wherein the thin film portion (7) is formed by laminating a plurality of thin films
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(8, 9). It is a coating structure of a microphone characterized by
[0010]
The invention according to claim 4 is the coating structure for a microphone according to claim 1
or 2, wherein the thin film portion (10) is formed of a single thin film (11). It is a structure.
[0011]
The invention according to claim 5 is a wind tunnel test apparatus for measuring the behavior of
the test object (1) generated by the flow of gas when the gas flows through the test object in the
wind tunnel measurement unit (4). A wind tunnel test apparatus (2) comprising the coating
structure (6) of the microphone (5) according to any one of claims 1 to 4.
[0012]
According to the present invention, wind noise and the like can be reduced, and aerodynamic
noise and the like generated from the test object can be measured with high accuracy.
[0013]
First Embodiment Hereinafter, a first embodiment of the present invention will be described in
detail with reference to the drawings.
FIG. 1 is a plan view of a wind tunnel test apparatus according to a first embodiment of the
present invention.
FIG. 2 is a plan view seen from the II direction of FIG.
FIG. 3 is a cross-sectional view of the coating structure of the microphone in the wind tunnel test
apparatus according to the first embodiment of the present invention.
FIG. 4 is a cross-sectional view of the thin film portion of the coating structure of the microphone
in the wind tunnel test apparatus according to the first embodiment of the present invention.
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The test object 1 shown in FIG. 1 is a test object (test object) of a model or a real thing. The test
object 1 is, for example, a model that simulates (reduces) an actual railway vehicle, a current
collector (pantograph), and the like.
[0014]
The wind tunnel test device 2 is a device that measures the behavior of the test object 1
generated by the flow of air when the air is flowed to the test object 1 in the wind tunnel
measurement unit 3. The wind tunnel test apparatus 2 flows air to the test object 1 in the wind
tunnel measurement unit 3, for example, and the flow of the air causes an acoustic noise such as
aerodynamic noise generated from the test object 1 and / or the flow of the air. Measure the
pressure etc. which the test object 1 receives. The wind tunnel test apparatus 2 shown in FIG. 1 is
a closed-loop wind tunnel test apparatus including a wind tunnel measurement unit 3, a wind
tunnel 4, a microphone 5, a coating structure 6, and the like.
[0015]
The wind tunnel measurement unit 3 is a portion on which the test object 1 is installed, and as
shown in FIGS. 2 to 4, includes the fixed wall portion 3 a and the microphone housing portion 3
b. The fixed wall portion 3 a is a cylindrical portion surrounding the inside of the wind tunnel
measurement portion 3. The microphone housing portion 3b is a concave portion for housing the
microphone 5, and as shown in FIG. 3, a plurality of the microphone housing portions 3b are
formed at a position receded from the wall surface of the fixed wall portion 3a.
[0016]
A wind tunnel 4 shown in FIG. 1 is an apparatus for creating an artificial air flow to investigate
various aerodynamic problems experimentally. The wind tunnel 4 is provided with a fan (not
shown) for artificially blowing a wind having a certain property, a duct, a rectifier and the like,
and a nozzle portion 4a that jets air to make the wind tunnel measurement unit 3 have a uniform
flow. The nozzle unit 4 a is connected to the wind tunnel measurement unit 3.
[0017]
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The microphone 5 shown in FIGS. 2 to 4 is a device for detecting noise generated from the test
object 1 when air is allowed to flow through the test object 1, and is an acoustoelectric converter
for converting acoustic energy into electrical energy. Etc. As shown in FIG. 2, a plurality of
microphones 5 are arranged at predetermined intervals, and each of them constitutes a twodimensional microphone array. As shown in FIG. 3, the microphone 5 includes a diaphragm 5a, a
vibration pickup unit 5b, a main unit 5c, and the like. The microphone 5 is housed, for example,
in the microphone housing portion 3b in a state where the protective cap portion is removed
from the tip end and the vibrating surface 5d is exposed.
[0018]
The diaphragm 5a is a portion that converts sound waves into mechanical vibrations, and is
formed of a polymer thin film or the like. A vibrating surface (pressure receiving surface) 5d is
formed on the surface of the diaphragm 5a on the side receiving the sound from the sound
source, and the vibrating surface 5d is disposed at a position receding from the wall surface in
the fixed wall portion 3a. . The vibration pickup unit 5b is a mechanical-electrical converter that
converts mechanical vibration of the diaphragm 5a into an electrical signal, and is a piezoelectric
element or the like that outputs an electrical signal according to the magnitude of the vibration.
The main body 5c is a cylindrical case accommodating the diaphragm 5a, the vibration pickup 5b
and the like, and a protective cap (not shown) for protecting the diaphragm 5a can be detachably
attached to the tip of the main body 5c. .
[0019]
The covering structure 6 is a structure in which the vibrating surface 5 d of the microphone 5 is
covered with the thin film portion 7. The covering structure 6 is provided with a thin film portion
(film portion) 7 having flexibility as shown in FIGS. As shown in FIG. 4, the thin film portion 7 has
a gap from the vibrating surface 5d to cover and protect the vibrating surface 5d, and is disposed
substantially in the same plane as the wall surface of the fixed wall 3a. In this embodiment, it is
preferable to install the microphone 5 in the microphone housing portion 3b so that the gap
between the thin film portion 7 and the vibrating surface 5d is as small as possible. The thin film
portion 7 is formed by overlapping and bonding a plurality of thin films 8 and 9 and is fixed to
the wall surface of the fixed wall portion 3a. As the thin film portion 7, it is preferable to select a
material having a thickness and a weight that can smooth the flow of air and does not resonate in
response to the flow of air. The thin films 8 and 9 have base materials 8a and 9a having smooth
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surfaces, and adhesive material layers 8b and 9b formed by applying an adhesive material on the
back surfaces of the base materials 8a and 9a, and are made of polypropylene film Etc. It is an
adhesive tape made of synthetic resin made of The thin films 8 and 9 bond the adhesive layer 8b
and the adhesive layer 9b, and are fixed to the fixed wall portion 3a with the base 8a side facing
the vibrating surface 5d and the base 9a side facing the sound source ing. As shown in FIGS. 2
and 4, the thin film 9 is formed to be slightly longer in length and width than the thin film 8, and
the adhesive layer 9b of the thin film 9 is bonded to the wall surface of the fixed wall 3a. The
periphery of the thin film 8 is sandwiched and fixed between the wall surface of the fixed wall 3
a and the thin film 9.
[0020]
Next, the operation of the wind tunnel test apparatus according to the first embodiment of the
present invention will be described. As shown in FIG. 1, the test object 1 is placed in the wind
tunnel measurement unit 3, and air is ejected from the nozzle portion 4 a to flow the air to the
test object 1. As a result, the flow of air strikes the test object 1 and an aerodynamic sound is
generated from the test object 1. The aerodynamic sound is detected by the microphone 5 and
the aerodynamic sound is measured.
[0021]
Next, the operation of the coating structure of the microphone in the wind tunnel test apparatus
according to the first embodiment of the present invention will be described. As shown in FIGS. 2
and 3, the adhesive layer 9 b of the thin film 9 is attached to the wall surface of the fixed wall 3 a
so that the surface of the thin film 7 is substantially the same surface. Is covered by the thin film
portion 7. Therefore, as shown in FIG. 1, the thin film portion 7 prevents the air flow in the
vicinity of the vibrating surface 5 d from being disturbed when the air flows in the wind tunnel
measurement portion 3, and the air flows in the wind tunnel measurement portion 3. The thin
film portion 7 prevents air from directly striking the vibrating surface 5d. As a result, noise such
as wind noise and wind noise generated by air passing near the vibrating surface 5 d is
suppressed.
[0022]
The wind tunnel test apparatus and the coating structure of the microphone according to the first
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embodiment of the present invention have the following effects. (1) In the first embodiment, the
vibrating surface 5d is disposed at a position receded from the wall surface of the fixed wall
portion 3a, and the thin film portion 7 is disposed substantially in the same plane as the wall
surface of the fixed wall portion 3a. Therefore, the thin film portion 7 can prevent the air flow in
the vicinity of the vibrating surface 5d of the microphone 5 from being disturbed, and can
prevent the air flow from directly hitting the vibrating surface 5d. As a result, since generation of
noise such as wind noise and wind noise generated near the vibration surface 5 d can be
suppressed, aerodynamic noise and the like from the test object 1 to be originally measured can
be accurately measured.
[0023]
(2)
In the first embodiment, the thin film portion 7 is fixed to the wall surface of the fixed wall
portion 3a. As a result, the wall surface of the fixed wall portion 3a and the surface of the thin
film portion 7 become substantially the same surface, so the air flow near the vibrating surface
5d of the microphone 5 becomes smooth, and the air flow is disturbed near the vibrating surface
5d. You can prevent that.
[0024]
(3)
In the first embodiment, a plurality of thin films 8 and 9 are overlapped and adhered to form a
thin film portion 7. Therefore, the number of thin films 8 and 9 is arbitrarily selected in
accordance with the velocity of air flowing in the wind tunnel measurement unit 3 and the size of
the gap between the thin film unit 7 and the vibrating surface 5 d. , Weight and rigidity can be
easily adjusted.
[0025]
(4) In the first embodiment, since the wind tunnel test apparatus 2 includes the covering
structure 6, noise such as wind noise and wind noise near the vibration surface 5d of the
microphone 5 is reduced, and aerodynamic noise and the like from the test object 1 can be
reduced. It can measure accurately.
[0026]
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8
Second Embodiment FIG. 5 is a plan view of a coating structure of a microphone in a wind tunnel
test apparatus according to a second embodiment of the present invention.
FIG. 6 is a cross-sectional view of a coating structure of a microphone in a wind tunnel test
apparatus according to a second embodiment of the present invention. Below, about the part
same as the part shown to FIGS. 1-4, the same number is attached | subjected and detailed
description is abbreviate | omitted. The thin film portion 10 shown in FIGS. 5 and 6 is composed
of a thin film 11 and an adhesive layer 12. The thin film 11 is a polypropylene film or the like
similar to the thin film portion 7 shown in FIGS. 2 to 4, and is covered by the adhesive layer 12
so as to cover the vibrating surface 5d of the microphone 5 as shown in FIGS. It is stuck and fixed
to the wall surface of fixed wall 3a. The adhesive layer 12 is applied to the wall surface of the
fixed wall 3 a so as to surround the microphone housing 3 b. In the second embodiment, in
addition to the effect of the first embodiment, since the thin film portion 10 is formed of one thin
film 11, the thickness of the thin film portion 10 can be easily managed.
[0027]
Next, the coating structure of the microphone according to the embodiment of the present
invention will be described. In order to verify the sound wave transmission characteristics of the
thin film portion 7 shown in FIGS. 1 to 4 and the dark noise reduction effect of the thin film
portion 7, experiments on the characteristics of the thin film portion 7 were performed. First, a
50 μm-thick polypropylene film (a transparent adhesive tape (trade name: SCOTCH) made by
Sumitomo 3M Ltd.) having an adhesive property on one side is attached as shown in FIGS. At the
same time, the vibration surface 5d of the microphone 5 is covered so as to be protected and
attached to the wall surface of the fixed wall 3a. The size of the rectangular area shown in FIG. 2
was 900 × 500 mm, and a film was attached so as to cover the microphone 5 in this area. The
experiment was conducted using a closed-drum wind tunnel test apparatus in the Wind Tunnel
Technology Center (Yonehara) of the Railway General Research Institute.
[0028]
(Sound Wave Transmission Property) FIG. 7 is a graph showing the test results of the sound wave
transmission property of the film in the coating structure of the microphone according to the
example of the present invention. The vertical axis shown in FIG. 7 is the sound pressure level
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difference (dB) between the case where the film is applied and the case where the film is not
applied, and the horizontal axis is the frequency (Hz). The test of the sound wave transmission
characteristics was performed by generating sounds (white noise) having equal power in a
constant frequency range from a speaker which is a sound source for sound measurement under
windless conditions. The graph shown in FIG. 7 shows the difference between the sound pressure
level measured by the microphone when the film is not covered by the film and the sound
pressure level measured by the microphone when the film is covered by the film The effect of
coating the vibrating surface with a film on the measurement results of the microphone is
evaluated. In general, when a film covers the vibrating surface, it is desirable that the influence
on the measurement results of the microphone be as small as possible, and even if the sound
pressure level changes, it is preferable to change uniformly over a wide frequency band. As
shown in FIG. 7, the effect of the film coating was at most about 1.5 dB at most, and it was
confirmed that the effect on the measurement results of the microphone was extremely small.
[0029]
(Dark Noise Reduction Effect) FIG. 8 is a graph showing measurement results of background
noise by a film in a coating structure of a microphone according to an embodiment of the present
invention. The vertical axis shown in FIG. 8 is the sound pressure level (dB), and the horizontal
axis is the frequency (Hz). Verification of the background noise reduction effect was performed
by removing the test object 1 from the inside of the closed cylinder and measuring the
background noise in the closed cylinder under a blowing condition of 50 m / s. Here, the
background noise is a sound other than that when focusing on a specific sound when a plurality
of sounds are simultaneously present, and, for example, when considering an aerodynamic sound
in a closed cylinder, this aerodynamic force The noise of the fan in the closed cylinder when
there is no sound is called the background noise to the aerodynamic noise. As shown in FIG. 8,
compared with the case where the vibrating surface is not covered with the film (without the
film), when the vibrating surface is covered with the film (with the film), about 7 to 15 dB in the
frequency range up to 5 kHz. Noise reduction effects such as wind noise and wind noise were
confirmed.
[0030]
From the above, even if the film is covered with the vibrating surface, the influence on the
measurement result of the microphone is extremely small, and the effect of reducing the wind
noise and wind noise by the film has been confirmed. In the case where the number of films is
small, a problem which is considered to be caused by resonance occurs in a frequency range of 5
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10
kHz band or more, and it is considered that the level of sound pressure received is increased by
installing the films. Although this effect is reduced by increasing the number of films, it is
considered that the performance in the high frequency band is lowered to make it difficult to
pass sound waves. For this reason, it is necessary to pay close attention to the relationship
between the thickness and the performance of the entire films superposed. On the other hand,
when a paper tape was used instead of the film, the sound was amplified at a specific frequency,
and the effect of reducing wind noise was low.
[0031]
(Other Embodiments) The present invention is not limited to the embodiments described above,
and various modifications or changes are possible as described below, and these are also within
the scope of the present invention. (1) In this embodiment, the closed-tunnel-type wind tunnel
test apparatus 2 has been described as an example, but the present invention can be applied to
an open-body-type wind tunnel test apparatus or the like. For example, the fixed wall 3a may be
disposed at a position apart from the air flow of the open cylinder, and the vibrating surface 5d
of the microphone 5 accommodated in the microphone accommodation unit 3b may be covered
by the thin film unit 7. Moreover, although the case where air was flowed to the wind tunnel
measurement part 3 was mentioned as the example and demonstrated in this embodiment, this
invention is applicable also when flowing gas other than air to the wind tunnel measurement part
3. FIG.
[0032]
(2)
In this embodiment, the case where the thin film portion 7 is fixed to the fixed wall portion 3a is
described as an example, but the present invention is not limited to this. For example, the fixed
wall 3a and the like may be omitted, the protective cap may be removed from the tip, and the
covering structure of the microphone 5 provided with the thin film 7 covering the vibrating
surface 5d may be configured. In this case, not only when the microphone 5 is used in the openbody type wind tunnel test apparatus but also when the microphone is used outdoors etc., it is
possible to prevent the air flow from directly hitting the vibrating surface. . In this embodiment,
the adhesive tape having the adhesive layers 8b and 9b on one side of the base members 8a and
9a is described as an example of bonding to the wall surface of the fixed wall 3a. The material
can also be applied and adhered to the wall surface of the fixed wall 3a.
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[0033]
It is a top view of the wind tunnel test equipment concerning a 1st embodiment of this invention.
It is the top view seen from the II direction of FIG. It is sectional drawing of the coating | coated
structure of the microphone in the wind tunnel test apparatus which concerns on 1st
Embodiment of this invention. It is sectional drawing of the thin film part of the coating | coated
structure of the microphone in the wind tunnel test apparatus which concerns on 1st
Embodiment of this invention. It is a top view of the covering structure of the microphone in the
wind tunnel test equipment concerning a 2nd embodiment of this invention. It is sectional
drawing of the coating | coated structure of the microphone in the wind tunnel test apparatus
which concerns on 2nd Embodiment of this invention. It is a graph which shows the test result of
the sound wave transmission characteristic by the film in the coating | coated structure of the
microphone which concerns on the Example of this invention. It is a graph which shows the
measurement result of the background noise by the film in the coating | coated structure of the
microphone concerning the Example of this invention.
Explanation of sign
[0034]
DESCRIPTION OF SYMBOLS 1 test object 2 wind tunnel test apparatus 3 wind tunnel
measurement part 3a fixed wall part 3b microphone housing part 4 wind tunnel 5 microphone
5a diaphragm 5d vibration surface 6 covering structure 7 thin film part 8,9 thin film 8a, 9a base
material 8b, 9b adhesive Layer 10 Thin film part 11 Thin film 12 Adhesive material layer
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