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JPH11183314

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JPH11183314
[0001]
[Technical Field of the Invention] The present invention relates to a test piece disposed in a
measuring tank of a circulating water tank for circulating water filled in a substantially annular
cavity, and a back noise generated from the test piece It is related to the circulating water tank
acoustic measurement device which measures it with high sensitivity by separating it from the
above. More specifically, at least one of the upper and lower surfaces and the left and right side
of the measuring cylinder at the position where the specimen is arranged The present invention
relates to a circulating water tank acoustic measurement apparatus in which a box-shaped
measurement trough filled with water is provided, and a bowl-like sound absorbing material in
which a wave receiver is embedded at the tip end side is disposed in the measurement trough.
[0002]
2. Description of the Related Art Generally, when a ship is traveling, if there is a large amount of
sound generated from a propeller or the like, vortices or cavitation or the like is often generated.
In such a case, the ship is Impact the propulsion efficiency of In addition, in the case of surveying
the sea using underwater acoustic equipment (receiver) such as a marine research vessel,
propeller cavitation noise has a problem such as adversely affecting the survey.
[0003]
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Therefore, as shown in FIG. 6, for example, as shown in FIG. 6, a flow of water flowing in the
water channel 2 of the circulating water tank 1 in order to reduce noise and prevent cavitation of
the propeller for the ship and to quiet the ship while traveling. A sample 3 such as a propeller or
a ship model is disposed in the inside, and the sound generated from the sample 3 is measured. A
measuring cylinder 4 having a substantially rectangular cross section is provided at the upper
center of the substantially annularly formed cavity-like water channel 2 of the circulating water
tank 1, and a circulating pump 5 is provided at the lower center of the water channel 2. The
circulation pump 5 is configured to be rotationally driven by an electric motor 6 disposed
outside.
[0004]
The hollow water channel 2 is filled with water, and the rectified water circulates in the water
channel 2 when the motor 6 is operated. In addition, the test body 3 is disposed in the
measurement cylinder 4, and when the test body 3 is a propeller, the propeller is rotationally
driven by a motor (not shown). Further, an acoustic measurement instrument or device for a
circulating water tank is provided inside or outside of the measuring cylinder 4 so as to measure
the sound generated from the specimen 3 disposed in the measuring cylinder 4. There is.
[0005]
The acoustic measuring instrument or device for the circulating water tank is one in which the
wave receiver 9 (submersible microphone) is disposed in the rectifying body 8 provided in the
water flow (direction perpendicular to the paper surface) in the measuring cylinder 4 . Next, FIG.
8 is a cross-sectional view of a conventional example of a circulating water tank acoustic
measurement device, and FIG. 9 shows a cross-sectional view taken along line A-A of FIG. 8
(Naoaki Okamura, Toshio Asano, Prediction of propeller cavitation noise And Ship Measurement,
Proceedings of the Japan Institute of Shipbuilding Fall Fall Sessions, November, 1988, No. 164,
pp. 43-53).
[0006]
The acoustic measurement unit 7a shown in FIG. 8 has an acoustic window 10 (a window made
of a material such as acrylic resin that easily transmits a sound wave) provided on the upper
surface of the measurement barrel 4a, and a box-shaped measurement trough 11 (water The
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receiver 9a is installed in the measurement trough 11 via a support member (not shown). In the
figure, reference numeral 12 denotes a reflector for reflecting the reflected sound from the back
side (upper side) of the receiver 9a.
[0007]
A rotating shaft 13 is provided at the center of the measuring barrel 4 a along the longitudinal
direction, and a propeller 14 is provided on the rotating shaft 13 and rotated to measure sound
waves generated from the propeller 14. Further, FIG. 10 shows a cross-sectional view of another
conventional example of the circulating water tank acoustic measurement apparatus, and the
acoustic measurement unit 7b is provided with an acoustic window 10a on the lower surface of
the measurement barrel 4b, and the measurement trough 11a below the acoustic window 10a. ,
And a plurality of sound absorbing members 15 are provided on the inner wall of the
measurement trough 11a, and a plurality of wave receivers 9b are disposed in a plane between
the sound absorbing member 15 and the acoustic window 10a to form the receiver group 9B. It
is a thing.
[0008]
Then, since it is considered that there is a difference in the time for the sound waves emitted
from the sound source 16 to reach the respective receivers 9b of the receiver group 9B, the
difference is used as a phase difference to overlap the signals from the respective receivers 9b.
Thus, the signal in the direction of the sound source 16 is emphasized. Therefore, the receiver
group 9B can have directivity in a specific direction. Reference numeral 12a denotes a reflector
for reflecting the sound wave from behind (below).
[0009]
However, the above-described conventional examples have the following problems. That is,. In
the conventional example shown in FIG. 7, the rectifying body 8 disposed in the measuring
cylinder 4 disturbs the flow of water to generate noise, and the S / N ratio of the measurement
data decreases. . In the conventional example shown in FIGS. 8 and 9, since the wave receiver 9a
is separated from the water flow in the measuring cylinder 4a, although such noise does not
occur, the distance from the propeller as the specimen 14 increases. Moreover, the attenuation
when transmitting through the acoustic window 10 reduces the level of the received sound at the
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receiver 9a. . In the conventional example shown in FIG. 10, by arranging and combining the
plurality of wave receivers 9b in a plane, it is possible to suppress the attenuation (reduction of
the received sound level) by the acoustic window 10a. And the sound wave reflected by the
reflection plate 12a behind the receiver 9b mix, and this affects the directivity of the receiver
group 9B.
[0010]
The present invention has been devised focusing on such conventional problems, in which the
sound generated from various specimens placed in the water flow in the channel of the
circulating water tank is separated from the background noise to be highly sensitive. Since it can
be measured and the wave receiver is embedded and integrally formed in the sound absorbing
material, a frame for attaching the wave receiver, reflection of sound of a signal line connected to
the wave receiver, etc. An object of the present invention is to provide a circulating water tank
acoustic measurement device capable of suppressing influence and always performing high
sensitivity measurement.
[0011]
SUMMARY OF THE INVENTION In order to achieve the above object, the present invention
achieves at least one of the upper and lower surfaces and the left and right side surfaces of the
measuring cylinder at the position where the specimen is disposed through an acoustic window
which easily transmits sound waves. A box-shaped measurement trough filled with water is
provided, and the rear end side of a bowl-shaped sound absorbing material whose receiver is
embedded at the front end side on the inner wall opposite to the acoustic window of the
measurement trough is separated by a predetermined distance. The gist of the invention is that
the plurality is disposed.
[0012]
The wedge-shaped sound absorbing material in which the wave receiver is embedded is made of
a rubber-like elastic material such as porous rubber material or resin material, and this sound
absorbing material is separated by half wave length of sound wave to be absorbed along the
direction of water flow. The solution is to solve this problem.
The signal lines of the receiver embedded in each of the sound absorbing materials are
embedded in the sound absorbing material and drawn out of the measurement trough.
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[0013]
The present invention is configured as described above, and the sound waves generated from the
specimen pass through the water in the measuring cylinder and the acoustic window to reach a
plurality of surface-arranged receivers.
By superimposing the respective signals using the phase difference of the signals obtained by the
respective receivers, directivity can be obtained, and the position of the sound source of the
sound wave can be known. Since the sound waves propagated behind the plurality of receivers
are absorbed by the sound absorbing material of the measurement trough, the reflected wave
reflected by the inner wall of the measurement trough is absorbed, and the measurement can be
performed with a high S / N ratio.
[0014]
When the sound absorbing material is formed into a wedge shape made of porous rubber and
provided at an interval of half the wavelength of the sound wave to be absorbed along the flow
direction of water, unnecessary sound waves are removed, so a high S It can measure by / N
ratio. Each receiver is integrally embedded in a sound absorbing material made of chloroprene
rubber or a synthetic resin material, and the signal lines connected to each receiver are also
embedded in the sound absorbing material and drawn out of the measurement trough In this
case, it is possible to suppress the influence of the reflection of the sound of the signal line
connected to the mount base for mounting the wave receiver to the wave receiver, etc. and the
wave receiver, and also for vibration isolation, it is made of rubbery elastic material It is possible
to damp the vibration with a sound absorbing material.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be
described below with reference to the attached drawings. FIG. 1 is a cross-sectional view showing
an embodiment of a circulating water tank acoustic measurement device according to the present
invention, wherein at least one surface (four in this embodiment) of upper and lower surfaces
and left and right side surfaces of a measuring cylinder 20 formed into a rectangular cross
section. The acoustic window 21 made of a material (for example, acrylic resin) which easily
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transmits the sound wave is provided on the upper side.
[0016]
The above-mentioned "easy to transmit the sound wave" means the property that the sound wave
transmits with almost no reflection or refraction. Box-shaped measurement troughs 22, 23, 24,
25 are respectively provided on upper and lower surfaces and left and right side surfaces of the
measurement cylinder 20 via an acoustic window 21, and inner wall surfaces of the
measurement troughs 22, 23, 24, 25 In FIG. 2 to FIG. 4, a rubber-like elastic material (in this
embodiment, there may be chloroprene rubber but may be made of a resin material) comprising
a ridge-like protrusion 26a and a support 26b. A base end 26 c of the sound absorbing material
26 as a material is attached to the acoustic window 21.
[0017]
A small piezoelectric rubber receiver 27 is embedded in the sound absorbing material 26 on the
side of the protrusion 26a, and the sound absorbing material 26 includes a base rubber 28 and a
cover rubber, as shown in FIGS. In the inner central portion of the base rubber 28 on the side of
the protrusion 26a, a recess 30 for accommodating the wave receiver 27 and a wave receiver
communicating with the recess 30 and extending in the longitudinal direction A signal line
receiving groove 32 for receiving the 27 signal lines 31 is formed.
[0018]
Further, a plurality of sound absorbing holes 33 are formed in the inner wall surface of the base
rubber 28 on both sides of the signal line receiving groove 32, and the sound absorbing holes 33
are formed from the side of the protrusion 26 a of the sound absorbing material 26. It is formed
so that an area may become large sequentially toward the edge part 26c.
The plurality of sound absorption holes 33 are not limited to those formed so that the area
gradually increases from the side of the protrusion 26a toward the base end 26c as described
above, It is also possible to form less.
[0019]
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In addition, a water injection hole 34 communicating with the recess 30 accommodating the
wave receiver 27 is formed on the side surface of the protrusion 26 a of the base rubber 28, and
the support plate 35 is formed in the signal line accommodation groove 32. Is attached. The
sound absorbing material 26 configured as described above embeds the wave receiver 27 in the
recess 30 formed in the inner central portion on the side of the protrusion 26 a of the base
rubber 28, and the wave receiver 32 in the signal line receiving groove 32. 27, the signal line 31
is embedded, the end of the signal line 31 is drawn out from the base end 26c of the sound
absorbing material 26, and the cover rubber 29 is superposed on the base rubber 28 and
integrally molded by adhesion or the like. is there.
[0020]
The plurality of sound absorbing members 26 configured in this manner are special mounts for
mounting the wave receiver 27 by attaching the side of the ridged protrusion 26 a in which the
wave receiver 27 is embedded toward the acoustic window 21. Also, it is possible to suppress the
influence of the reflection of the sound of the signal line connected to the wave receiver 27 and
the like, and it is possible to always perform high-sensitivity measurement. A water supply and
drainage pipe (not shown) is connected so that the inside of the measurement troughs 22, 23,
24, 25 is filled with water.
[0021]
When a test piece (for example, a propeller) 36 is disposed in such a measurement cylinder 20
and rotated, a sound wave is generated from the test piece 36. The generated sound wave
propagates in the water in the measurement cylinder 20 and spreads around, and the sound
wave propagated in the arrow X direction passes through the acoustic window 21 and is received
by the wave receiver 27 embedded in the sound absorbing material 26 in the measurement
trough 22. To reach. Since there is a phase difference in the time until the sound from the
specimen 36 reaches each receiver 27, the direction of the specimen 36 can be obtained by
superposing the signals from each receiver 27 with the phase difference. Signal can be
emphasized and directional. Also, the receiver 27 can know the position of the sound source of
the sound wave by changing the phase difference.
[0022]
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On the other hand, the sound wave (arrow E) propagated except for the embedded portion of the
wave receiver 27 is absorbed by the ridged protrusion 26a and the support 26b of the sound
absorbing material 26, and the sound generated from the specimen 36 is separated from the
background noise. Measurement with high sensitivity. Next, FIG. 5 shows another embodiment of
the sound absorbing material, and the sound absorbing material 40 of this embodiment is
composed of a ridged protrusion 40a and a support 40b, and two sheets of the sound absorption
material 40 are provided on the front and back of the support 40b. The rubber-like elastic
materials 41a and 41b are bonded together to form an integral unit, and the wave receiver 27
and the signal line 31 are embedded in the central portion in the width direction of the
protrusion 40a.
[0023]
The sound absorbing material 40 of this embodiment is lower than the height of the sound
absorbing material 26 of the first embodiment, and is designed to have the most sound absorbing
effect as the sound absorbing material 40 for a wide frequency band (near frequency 10 to 15
kHz). It is done. Furthermore, in order to correspond to a wide frequency band, it becomes
possible by bonding sound absorbing materials of different heights. In addition, although acrylic
was used as a material of the acoustic window 21 in the said embodiment, it is not limited to this,
If water can be interrupted | blocked and a sound wave can be permeate | transmitted, aluminum
honeycomb material (honeycomb-like aluminum plate It is also possible to use one in which both
sides are closed with an aluminum plate.
[0024]
According to the present invention, at least one of the upper and lower surfaces and the left and
right side surfaces of the measuring cylinder at the position where the specimen is disposed as
described above is box-shaped filled with water through an acoustic window that easily transmits
sound waves. A measurement trough is provided, and the rear end side of a sound absorbing
material made of a rubber-like elastic material in the form of a bowl is embedded at the tip end
side on the inner wall opposite to the acoustic window of the measurement trough. Since it is
arranged in multiple pieces, the sounds generated from various specimens placed in the water
flow in the water channel of the circulating water tank can be separated from the background
noise and measured with high sensitivity, and the sound absorbing material Since the wave
device is embedded and integrally formed, the influence of the reflection of the sound of the base
for attaching the wave receiver, the signal line connected to the wave receiver, etc. can be
suppressed, and always high sensitivity There is an effect that can be measured.
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[0025]
Brief description of the drawings
[0026]
1 is a cross-sectional view of a circulating water tank acoustic measurement device showing an
embodiment of the present invention.
[0027]
2 is an overall perspective view of a sound absorbing material in which a small receiver is
integrally embedded.
[0028]
3 is a plan view of a sound absorbing material in which a small receiver is integrally embedded.
[0029]
4 is a front view of a sound absorbing material in which a small receiver is integrally embedded.
[0030]
5 is a perspective view showing another embodiment of a sound absorbing material for a wide
frequency band.
[0031]
6 is an external perspective view of a conventional circulating water tank for measuring the
sound of the sample.
[0032]
7 is a partially cutaway perspective view of a conventional example of the circulating water tank
acoustic measurement device for measuring the sound generated from the sample disposed on
the measurement cylinder.
[0033]
8 is a cross-sectional view of another conventional example of the circulating water tank acoustic
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measurement device.
[0034]
9 is a cross-sectional view taken along the line AA of FIG.
[0035]
10 is a cross-sectional view of another conventional example of the circulating water tank
acoustic measurement device.
[0036]
Explanation of sign
[0037]
Reference Signs List 20 measuring cylinder 21 acoustic window 22, 23, 24, 25 measurement
trough 26 sound absorbing material 26a ridged protrusion 26b support portion 26c base end 27
piezoelectric rubber type wave receiver 28 base rubber 29 cover rubber 30 recess 31 signal line
32 Signal line receiving groove 33 Sound absorbing hole 34 Injection hole 35 Support plate 36
Test object (eg propeller)
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