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JPH10111169

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DESCRIPTION JPH10111169
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
fluid noise measuring sensor mounted on a wall in contact with a water flow or the like for
measuring fluid noise.
[0002]
2. Description of the Related Art In designing a ship's hull, its external shape is an important
factor that greatly affects the wave resistance, stability, quietness and the like. Therefore, it is
necessary to analyze the relationship between the noise generated in the boundary layer of the
hull surface during navigation and the outer shape of the hull, and reflect the obtained result in
the design. However, in the boundary layer of the hull surface during navigation There is not
much research on the relationship between the generated noise and the external shape of the
hull, and the measurement of fluid noise generated from the wall in contact with the water flow
etc. is based on an empirical formula etc. obtained using a water tank and a model etc. An
approximation is being made. Such laboratory-level methods are difficult to obtain accurate data
of fluid noise because they are analogy rather than using actual vessels.
[0003]
Therefore, a method has been proposed in which a commercially available small hydrophone is
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placed in the flow field to measure fluid noise. On the other hand, since the fluid noise attenuates
exponentially with distance, the hydrophone needs to be placed close to the flow field.
[0004]
However, since the commercially available hydrophone is expensive, the mold for protecting the
built-in element is thick, and the length is also as long as 50 mm. Since the acoustic window to be
formed had to be enlarged to fit the hydrophone and could not be installed close to the flow field,
it was difficult to make accurate fluid noise measurement.
[0005]
Therefore, an object of the present invention is to provide a fluid noise measurement sensor
capable of solving the above-mentioned problems and accurately measuring fluid noise such as
water flow with a simple configuration.
[0006]
[Means for Solving the Problems] In order to achieve the above object, the present invention is a
fluid noise measuring sensor mounted on a wall in contact with a water flow or the like for
measuring fluid noise thereof, comprising a measuring surface of a watertight container facing
the wall. A main electroacoustic transducer is provided on the front surface, and a secondary
electroacoustic transducer for noise cancellation is provided on the back surface of the
measurement surface.
[0007]
According to the above configuration, the measurement surface of the watertight container
vibrates in accordance with the vibration of the hull, so that the main and sub electroacoustic
transducers simultaneously vibrate.
By superimposing the signal of the sub electro-acoustic transducer on the signal of the main
electro-acoustic transducer, the signal corresponding to the vibration of the ship is erased, and
only fluid noise can be taken out, and measurement can be performed with high accuracy.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will
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now be described in detail with reference to the attached drawings.
[0009]
FIG. 1 is a cross-sectional view showing an embodiment of a fluid noise measurement sensor of
the present invention.
[0010]
As shown in the figure, an attachment member (flat plate in the figure) attached to the hull and in
contact with a water flow (direction of arrow A) etc. is, for example, a part of a dome-shaped
cover.
The watertight container 2 is attached to the wall surface of 1).
The watertight container 2 is made of, for example, a metal such as stainless steel and is formed
in a closed bottomed cylindrical shape.
The watertight container 2 has its flange portion 3 fixed to the mounting member 1 by a bolt
(not shown) (fixed with an adhesive or a screw is formed on the outer periphery of the watertight
container 2 and the inner periphery of the mounting member 1 You may do it.).
A main electroacoustic transducer (for example, an electrode is formed on both sides of a small
piece made of piezoelectric rubber or piezoelectric ceramic, and is compact) 5 is provided in the
recess 4 on the outer side (upper side in the figure) of the watertight container 2 A waterproof
rubber (for example, silicone rubber) 6 is filled in the recess 4 so as to cover the main
electroacoustic transducer 5. The surface (measurement surface) 10 of the waterproof rubber 6
is formed to be a smooth surface without unevenness as in the surface of the mounting member
1. A through hole 8 is formed in a lid (partition) 7 of the watertight container 2, and a waterproof
cable 9 from the main electroacoustic transducer 5 is penetrated. On the back surface of the
measurement surface 10 of the watertight container 2, a secondary electroacoustic transducer
11 having the same characteristics as the main electroacoustic transducer 5 is provided. The
waterproof cable 9 of the main electroacoustic transducer 5 and the waterproof cable 12 of the
auxiliary electroacoustic transducer 11 are connected such that the polarity of the output signal
is reversed. A fluid noise measurement sensor is configured by the watertight container 2, the
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main electroacoustic transducer 5, and the auxiliary electroacoustic transducer 11.
[0011]
In such a fluid noise measurement sensor, since the main electroacoustic transducer 5 is closest
to the water flow, it receives the fluid noise and the vibration of the partition 7. Since the
secondary electroacoustic transducer 11 is disposed at a position cut off from the water flow,
only the vibration of the partition 7 is received. Therefore, by superimposing the output signals
of both electro-acoustic transducers 5 and 11, the vibration component in the direction of arrow
B of partition 7 due to the vibration of the ship is canceled, so that only fluid noise can be
measured with a high S / N ratio. it can. Moreover, since a commercially available hydrophone is
not used, downsizing is possible.
[0012]
According to the present embodiment, in the fluid noise measurement sensor attached to the wall
surface in contact with the water flow and the like to measure the fluid noise, the main
electroacoustic transducer is provided on the surface of the measurement surface of the
watertight container facing the wall surface Since the sub-electro-acoustic transducer for noise
cancellation is provided on the back surface of the measurement surface, a small fluid noise
measurement sensor capable of accurately measuring fluid noise such as water flow can be
realized with a simple configuration. In the present embodiment, the water-tight container has
been described as being formed in a cylindrical shape with a closed bottom, but the present
invention is not limited to this, and may have a box shape or an elliptical cylindrical shape. Also,
the mounting member may be a bulkhead of the hull.
[0013]
As described above, according to the present invention, the following excellent effects are
exhibited.
[0014]
The main electro-acoustic transducer is provided on the surface of the measurement surface of
the watertight container facing the wall, and the sub-electro-acoustic transducer for noise
cancellation is provided on the back of the measurement surface. It can be measured accurately.
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[0015]
Brief description of the drawings
[0016]
1 is a cross-sectional view showing an embodiment of a fluid noise measurement sensor of the
present invention.
[0017]
Explanation of sign
[0018]
2 Watertight container 5 Main electroacoustic transducer 7 Partition wall (lid part) 11 Secondary
electroacoustic transducer 10 Measurement surface
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