JP2987433B2 - Circulating water tank acoustic measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of arranging a specimen in a measuring cylinder of a circulation water tank for circulating water filled in a substantially annular cavity, and generating a noise generated from the specimen in a background noise. The present invention relates to a circulating water tank acoustic measurement device that measures with high sensitivity by separating from the measurement tank.More specifically, at least one of the upper and lower surfaces and the left and right sides of the measurement cylinder at the position where the specimen is arranged, through an acoustic window that easily transmits sound waves The present invention relates to a circulating water tank acoustic measurement device in which a box-shaped measurement trough filled with water is provided, and a wedge-shaped sound-absorbing material having a receiver buried at the distal end side is provided in the measurement trough.

[0002]

2. Description of the Related Art In general, when the sound generated by a propeller or the like when a ship is traveling is large, a vortex is generated,
In addition, cavitation and the like often occur, and in such a case, the propulsion efficiency of the ship is affected. In addition, when an underwater acoustic device (receiver) is used to survey the sea, such as an oceanographic research ship, there has been a problem that propeller cavitation noise has an adverse effect on the survey.

[0003] Therefore, in order to reduce noise and prevent cavitation of a propeller for a ship, and to quiet the running ship, as a simulation test measuring device, for example, as shown in FIG. A sample 3 such as a propeller or a ship model is arranged in a flowing water flow, 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 a substantially annular hollow 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 arranged outside.

The cavity-shaped water channel 2 is filled with water, and rectified water circulates in the water channel 2 when the electric motor 6 operates. The test piece 3 is arranged in the measuring cylinder 4, and when the test piece 3 is a propeller, the propeller is configured to be rotationally driven by an electric motor (not shown).
An acoustic measuring instrument or device for a circulating water tank is provided inside or outside the measuring cylinder 4.
The sound generated from the specimen 3 arranged in the inside is measured.

[0005] In the acoustic measuring instrument or device for the circulating water tank, a receiver 9 (underwater microphone) is arranged in a rectifier 8 provided in a water flow (a direction perpendicular to the paper surface) in the measuring cylinder 4. Things. Next, FIG. 8 is a cross-sectional view of a conventional example of a circulating water tank acoustic measurement device, and FIG. 9 is a cross-sectional view taken along line AA of FIG. 8 (Naoaki Okamura, Toshio Asano, prediction of propeller cavitation noise). And actual ship measurement, 1988
Proceedings of the Autumn Meeting of the Shipbuilding Society of Japan, No. 164, pp. 43-53).

[0006] The acoustic measuring section 7a shown in FIG.
An acoustic window 10 (a window made of a material such as acrylic resin that easily transmits sound waves) is provided on the upper surface of the device, and a box-shaped measurement trough 11 (water pool) is provided thereon, and the measurement trough 11 is provided in the measurement trough 11. The receiver 9a is installed via a support member (not shown). In the figure, reference numeral 12 denotes a receiver 9a.
2 shows a reflector for reflecting a reflected sound from behind (above).

At the center of the measuring cylinder 4a, a rotating shaft 13 is provided along the longitudinal direction. A propeller 14 is provided on the rotating shaft 13 and rotated to measure a sound wave generated from the propeller 14. FIG. 10 is a cross-sectional view of another conventional example of the circulating water tank acoustic measurement device, and shows the acoustic measurement unit 7b.
Is provided with an acoustic window 10a on the lower surface of the measuring cylinder 4b,
0a is provided below the measurement trough 11a.
A plurality of sound absorbing members 15 are provided on the inner wall of a, and a plurality of receivers 9b are arranged in a plane between the sound absorbing member 15 and the acoustic window 10a to form a receiver group 9B.

Since it is considered that there is a difference in the time when the sound wave emitted from the sound source 16 reaches each of the receivers 9b of the receiver group 9B, a signal from each of the receivers 9b is used as a phase difference. Are superimposed, the signal in the direction of the sound source 16 is emphasized. Therefore, the receiver group 9B can have directivity in a specific direction. In addition, 12a is a reflector for reflecting sound waves from behind (below).

[0009]

However, the above-mentioned prior arts have the following problems. That is,. In the conventional example shown in FIG. 7, the rectifier 8 disposed in the measuring cylinder 4 disturbs the flow of water, so that noise is generated, and the S / N ratio of the measurement data decreases. . In the conventional example shown in FIGS. 8 and 9, since the receiver 9a is separated from the water flow in the measuring cylinder 4a, such noise does not occur, but the distance from the propeller as the test piece 14 increases. Furthermore, the level of the sound received by the wave receiver 9a decreases due to attenuation when the sound passes through the acoustic window 10. . In the conventional example shown in FIG. 10, the attenuation (reduction in received sound level) due to the acoustic window 10a can be suppressed by arranging and combining a plurality of wave receivers 9b in a plane.
Since the reflected wave on the inner wall of the measuring cylinder 4b and the sound wave reflected on the reflector 12a behind the receiver 9b are mixed, the directivity of the receiver group 9B is affected.

The present invention has been devised in view of such a conventional problem, and separates sounds generated from various specimens placed in a water flow in a channel of a circulation water tank from background noise. Measurement can be performed with high sensitivity, and the receiver is buried in the sound-absorbing material and integrally formed, so that the rack for mounting the receiver and the sound of the signal line connected to the receiver can be measured. It is an object of the present invention to provide a circulating water tank acoustic measurement device that can suppress the influence of reflection and the like and can always perform highly sensitive measurement.

[0011]

According to the present invention, in order to achieve the above object, at least one of the upper and lower surfaces and the left and right side surfaces of a measuring cylinder at a position where a specimen is arranged is provided through an acoustic window through which sound waves are easily transmitted. Provide a box-shaped measurement trough filled with water,
On the inner wall surface of the measurement trough opposite to the acoustic window, a plurality of rear end sides of a wedge-shaped sound absorbing material having a receiver buried at a front end side are arranged at predetermined intervals. It is.

The wedge-shaped sound-absorbing material in which the receiver is embedded is made of a rubber-like elastic material such as a porous rubber material or a resin material, and absorbs the sound-absorbing material in a half of a sound wave to be absorbed in the direction of the water flow. The problem is to be solved by providing them at wavelength intervals. The signal line of the receiver buried in each sound absorbing material is buried in the sound absorbing material and drawn out of the measurement trough.

According to the present invention, the sound wave generated from the specimen reaches the plurality of receivers arranged in a plane through the water and the acoustic window in the measuring cylinder. By superimposing the signals using the phase difference between the signals obtained by the respective receivers, directivity can be given, and the position of the sound source can be known. Sound waves that propagate behind multiple receivers are absorbed by the sound absorbing material of the measurement trough,
The reflected wave reflected on the inner wall of the measurement trough is absorbed and the high S
/ N ratio.

When the sound absorbing material is formed in a wedge shape made of porous rubber and provided at intervals of half a wavelength of a sound wave to be absorbed along the flow direction of water, unnecessary sound waves are removed. ,
It can be measured at a high S / N ratio. Each receiver is embedded in a sound absorbing material made of a material such as chloroprene rubber or synthetic resin material, and the signal line connected to each receiver is also embedded in the sound absorbing material and drawn out of the measurement trough. With this configuration, it is possible to suppress the influence of the base for mounting the receiver and the reflection of the sound of the signal line connected to the receiver, and the vibration isolation is also made of a rubber-like elastic material. It can be damped with a sound absorbing material.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing an embodiment of a circulating water tank acoustic measurement device according to the present invention, in which at least one of the upper and lower surfaces and left and right side surfaces of a measuring cylinder 20 formed in a hollow cross section (in this embodiment, four surfaces). On the upper side, there is provided an acoustic window 21 made of a material (for example, acrylic resin) that easily transmits sound waves.

[0016] The "easy transmission of sound waves" means that
It refers to the property of transmitting sound waves with almost no reflection or refraction. Box-shaped measurement troughs 22, 23, 24, 2 are provided on the upper and lower surfaces and left and right side surfaces of the measurement cylinder 20 through acoustic windows 21.
5 are provided respectively, and the measurement troughs 22, 23, 2
As shown in FIGS. 2 to 4, a rubber-like elastic material comprising a wedge-shaped protrusion 26a and a support 26b (in this embodiment, chloroprene rubber is used, but a resin material is used). A base end portion 26c of the sound absorbing material 26 made of a material may be attached toward the acoustic window 21.

In the inside of the sound absorbing member 26 on the side of the protrusion 26a, small receivers 27 of a piezoelectric rubber type are embedded, respectively.
As shown in FIGS. 2 to 4, the sound absorbing material 26 has a structure in which a base rubber 28 and a cover rubber 29 are bonded to each other. A concave portion 30 for accommodating the signal line 27 and a signal line accommodating groove 32 for accommodating the signal line 31 of the wave receiver 27 extending in the longitudinal direction communicating with the concave portion 30 are formed.

A plurality of sound absorbing holes 33 are formed on the inner wall surface of the base rubber 28 on both sides of the signal line accommodating groove 32, and the sound absorbing holes 33 are formed on the projections 26 a of the sound absorbing material 26. It is formed so that the area increases sequentially from the side toward the base end portion 26c. The plurality of sound absorbing holes 33
The sound absorbing holes 33 having a large area are not limited to those formed so that the area is sequentially increased from the protruding portion 26a side to the base end portion 26c as described above. It is possible.

Water injection holes 34 are formed on the side surfaces of the projections 26a of the base rubber 28 so as to communicate with the recesses 30 for receiving the receiver 27. A support plate 35 is attached. The sound absorbing material 26 configured as described above has the receiver 27 buried in the concave portion 30 formed at the inner center portion of the base rubber 28 on the side of the protrusion 26a, and the receiver 27 is provided in the signal line accommodating groove 32. 2
7, the terminal portion of the signal line 31 is pulled out from the base end portion 26c of the sound absorbing material 26, and the base rubber 28
The cover rubber 29 is superposed thereon and integrally formed by bonding or the like.

The plurality of sound absorbing members 26 configured as described above are attached to the acoustic window 21 by attaching the wedge-shaped projection 26a having the receiver 27 embedded therein toward the acoustic window 21.
7 can be suppressed, and the influence of the reflection of sound from the signal line connected to the receiver 27 can be suppressed, and measurement with high sensitivity can always be performed. The inside of the measurement troughs 22, 23, 24, 25 is connected to a water supply / drain pipe (not shown) so as to be filled with water.

When a specimen (for example, a propeller) 36 is arranged and rotated in the measuring cylinder 20, sound waves are generated from the specimen 36. The generated sound wave propagates through the water in the measuring cylinder 20 and spreads around, and the sound wave propagated in the arrow X direction passes through the acoustic window 21 to the receiver 27 embedded in the sound absorbing material 26 in the measuring trough 22. To reach. Since there is a phase difference in the time from when the sound from the specimen 36 reaches each of the receivers 27, the signal from each of the receivers 27 is superimposed on the phase difference to obtain the direction of the specimen 36. Is emphasized, and directivity can be provided. The receiver 27 can know the position of the sound source by changing the phase difference.

On the other hand, sound waves (arrow E) propagating other than the buried portion of the wave receiver 27 receive the wedge-shaped projections 26 a of the sound absorbing material 26.
The sound that is absorbed by the test piece 36 and absorbed by the support portion 26b can be separated from the background noise and measured with high sensitivity. Next, FIG. 5 shows another embodiment of the sound absorbing material. In this embodiment, the sound absorbing material 40 includes a wedge-shaped protrusion 40 a and a support 4.
0b, the two rubber-like elastic materials 41a and 41b are bonded together on the front and back surfaces of the support portion 40b, and are integrally formed. The signal line 31 is buried.

The sound absorbing material 40 of this embodiment is lower than the height of the sound absorbing material 26 of the first embodiment, and has the most sound absorbing effect as the sound absorbing material 40 for a wide frequency band (frequency around 10 to 15 kHz). It is designed to be. Further, in order to correspond to a wide frequency band, it is possible to bond sound absorbing materials having different heights. Although acrylic is used as the material of the acoustic window 21 in the above-described embodiment, the material is not limited to this. If it can block water and transmit sound waves, it is possible to use an aluminum honeycomb material (a honeycomb-shaped aluminum plate). It is also possible to use an aluminum plate that is closed on both sides).

[0024]

According to the present invention, a box shape filled with water is provided on at least one of the upper and lower surfaces and left and right side surfaces of the measuring cylinder at the position where the test piece is arranged as described above, through an acoustic window through which sound waves are easily transmitted. A measurement trough is provided, and a rear end side of a sound absorbing material made of a wedge-shaped rubber-like elastic material having a receiver buried at a distal end side thereof is provided at a predetermined interval on an inner wall surface facing the acoustic window of the measurement trough. The sound 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. Since the wave receiver is buried and integrally formed, the influence of the stand for mounting the wave receiver and the reflection of the sound of the signal line connected to the wave receiver can be suppressed, and the sensitivity is always high. There is an effect that the measurement of can be performed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a circulating water tank acoustic measurement device showing an embodiment of the present invention.

FIG. 2 is an overall perspective view of a sound absorbing material in which a small wave receiver is integrally embedded.

FIG. 3 is a plan view of a sound absorbing material in which a small wave receiver is embedded integrally.

FIG. 4 is a front view of a sound absorbing material in which a small wave receiver is integrally embedded.

FIG. 5 is a perspective view showing another embodiment of a sound absorbing material for a wide frequency band.

FIG. 6 is an external perspective view of a conventional circulating water tank for measuring the sound of a specimen.

FIG. 7 is a partially cutaway perspective view of a conventional example of a circulating water tank acoustic measurement device for measuring a sound generated from a test body arranged on a measurement cylinder.

FIG. 8 is a cross-sectional view of another conventional example of a circulating water tank acoustic measurement device.

FIG. 9 is a sectional view taken along the line AA of FIG. 8;

FIG. 10 is a cross-sectional view of another conventional example of a circulating water tank acoustic measurement device.

[Explanation of symbols]

REFERENCE SIGNS LIST 20 measuring cylinder 21 acoustic window 22, 23, 24, 25 measuring trough 26 sound absorbing material 26 a wedge-shaped projection 26 b support 26 c base end 27 piezoelectric rubber receiver 28 base rubber 29 cover rubber 30 recess 31 signal line 32 Signal line receiving groove 33 Sound absorption hole 34 Injection hole 35 Support plate 36 Specimen (for example, propeller)

Continued on the front page (72) Inventor Hiroshi Horii 2-1 Oiwake, Hiratsuka-shi, Kanagawa Yokohama Rubber Co., Ltd. Hiratsuka Works (72) Inventor Kaoru Nakamura 2-1 Oiwake, Hiratsuka-shi, Kanagawa Yokohama Rubber Hiratsuka Works (72) Inventor Kozo Ishimae 20-11, Kagi-no-Kitadai, Aoba-ku, Aoba-ku, Yokohama-shi, Kanagawa Prefecture 201 First Daigasaka Heights 201 (56) References JP-A-2-259440 (JP, A) JP-A-4-85145 (JP, U) (58) Field surveyed (Int.Cl. ⁶ , DB name) G01M 10/00 G01H 3/00 H04R 1/44 320

Claims (4)

(57) [Claims] 1. A circulating water tank acoustic measuring device for arranging a test body in a measuring cylinder of a circulating water tank for circulating water filled in a substantially annular cavity and measuring a sound generated from the test body. A box-shaped measurement trough filled with water is provided on at least one of the upper and lower surfaces and left and right side surfaces of the measurement cylinder at the position where the test specimen is disposed, through an acoustic window that easily transmits sound waves. On the inner wall surface facing the acoustic window, a plurality of rear end sides of a sound absorbing material made of a wedge-shaped rubber-like elastic material having a receiver buried at the front end side are arranged at predetermined intervals. Circulating water tank acoustic measurement device. 2. A wedge-shaped sound absorbing material in which said receiver is embedded,
2. The circulating water tank acoustic measurement device according to claim 1, wherein the sound absorbing material is made of a porous rubber material, and is provided at intervals of a half wavelength of a sound wave to be absorbed along the direction of the water flow. 3. A wedge-shaped sound absorbing material in which the receiver is embedded,
The circulating water tank acoustic measurement device according to claim 1, wherein the sound absorbing material is made of a synthetic resin material, and is provided at a half wavelength interval of a sound wave to be absorbed along the direction of the water flow. 4. The sound absorbing material according to claim 1, wherein the signal line of the receiver buried in each sound absorbing material is buried in the sound absorbing material and drawn out of the measurement trough. Circulating water tank acoustic measurement device.