JP2998927B2 - Underwater sound insulation structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circulating water tank used for measuring propellers and the like of a ship, which keeps a high cutoff frequency of a sound wave propagating in water at a low frequency and a low cutoff frequency. It relates to an underwater sound insulation structure that secures high water pressure and large volume of flowing water while blocking propagation.

[0002]

2. Description of the Related Art FIG. 2 is a schematic view showing an example of a conventional circulating water tank of this type. In the drawing, reference numeral 1 denotes a circulating pipe, which is usually about 7 m in height and about 13.5 m in width. Yes,
It is composed of an iron tube or the like having a thickness so as to withstand considerable water pressure. 2 is a water supply device provided on the first floor,
Reference numeral 3 denotes a measuring unit provided on the second floor. Water supply device 2
The water is constantly absorbed from the water absorption section 13 and water pressure is applied thereto, and water is supplied at a predetermined pressure from the water supply section 10, and the water is circulating in the circulation pipe 1.

[0003] Water supplied from the water supply device 2 is supplied to a water supply unit 1.
After passing through 0, the flow enters the rectification unit 11 whose diameter is expanded, the flow of water is adjusted by the rectification unit 11, and reaches the measurement unit 3 through the elbow unit 12. Various measuring devices (for example, a propeller dynamometer, a wake measuring device, and a noise measuring device) are installed in the measuring unit 3. A propeller to be measured is installed in the water flow of the measuring unit 3. , Power measurement, fluid measurement,
Noise measurement and the like are performed.

[0004]

Since the conventional circulating water tank as described above does not have a positive means for blocking noise propagating in water, relatively large cavitation noise can be measured in noise measurement. There has been a problem that it is not possible to measure a small fluid noise that occurs when the propeller is stationary. That is, in the conventional circulating water tank,
Since the noise generated from the pump constituting the water transmission device propagates in the circulation and is transmitted to the measurement unit, the noise of the measurement unit 3 is large, and it is difficult to measure small noise such as fluid noise. Note that some conventional circulating water tanks have taken measures such as using a low-vibration pump for the water supply device, placing the pump on a vibration isolator, and interposing an elastic member between the pump and the water channel. However, they can be expected to have anti-vibration effects but not to have sound insulation effects.

The present invention has been made to solve such a problem, and an object of the present invention is to provide an underwater sound insulation structure suitable for installation in a circulating water tank or the like. It is an object of the present invention to provide an underwater sound insulation structure capable of measuring small noise generated by an object to be measured by reducing the noise generated.

[0006]

The underwater sound insulation structure according to the present invention is provided on the water absorption side or the water supply side (or on the water absorption side and the water supply side) of a water supply device such as a pump, and is generated by the pump and propagates through the water. In the underwater sound insulation structure that insulates the noise, the underwater (sound speed of 1.5 km / sec.
And When the upper limit of the wavelength is set to λ, a branch pipe made of an acoustically soft pipe such as a rubber pipe having a diameter d of d ≦ λ / 1.3 is formed with air interposed therebetween. It is characterized in that a reinforcing member is provided on its outer periphery so as not to be in contact with each other, and is built in a required number of pressure-resistant reinforcing pipes determined from the amount of water supply per unit time. Therefore, noise from a noise source such as a pump can be shielded. Here, “acoustically soft” means that a certain medium ρc
If (intrinsic acoustic impedance: product of density ρ and sound velocity c) is smaller than water ρc, the substance is said to be acoustically softer than water, and vice versa.
For example, ρc of air is very small, about 1/3500 of ρc of water, and iron is 26 times as large as water. The rubber tube and the soft vinyl tube of the outside air have properties almost acoustically similar to air.

Another feature of the present invention is a circulating water tank provided with the above-described underwater sound insulation structure and used for measuring a propeller or the like of a ship. Therefore, the circulating water tank of the present invention can measure small noise generated by the object to be measured, such as the fluid noise described above.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a view for explaining an embodiment of the underwater sound insulation structure of the present invention. For example, in the circulating water tank shown in FIG. 2, the water absorption section 13 or the water transmission section 10 (or the water absorption section 13 and the water )used. As shown in FIG. 1, the underwater sound insulation structure of the present embodiment is formed of a necessary number of rubber materials or the like determined by a water supply amount (water supply pressure) per unit time in a pressure-resistant reinforcing pipe 100 for reinforcing the whole. A soft elastic branch pipe 101 is inserted, a reinforcing member 102 such as a metal or a fiber net is attached to the outer periphery of each elastic branch pipe 101, and air is interposed between the elastic branch pipes 101 so that they do not contact each other. It is composed.

[0009] As is well known, when an acoustically soft tube such as a rubber tube whose surroundings are in contact with air is filled with water, theoretically, in order for sound waves to propagate through the water, it is necessary to reduce the speed of sound in the water. Λ <1.3 × d, where λ is the wavelength of the sound at 1.5 km / sec.
Must be: That is, the diameter in the pipe is d = 7.
In the case of 5 cm, sound waves having a frequency of fc = 15 kHz or less theoretically do not propagate through this tube.

Therefore, if water is supplied or supplied through the elastic branch pipe 101 whose inner diameter d is determined in accordance with the upper limit λ of the wavelength of the noise generated from the water supply apparatus 2, theoretically, The noise generated by the motor is cut off and does not propagate in the circulation. However, since a desired amount of water supply (water supply pressure) cannot be obtained with only one elastic branch pipe 101, a plurality of elastic branch pipes 101 and a required number of elastic branch pipes 101 are provided in the pressure-resistant reinforcing pipe 100. If the elastic branch pipes 101 come into contact with each other, the condition of acoustic softness is not satisfied. Therefore, a reinforcing member 102 such as a metal or a fiber net is provided around each elastic branch pipe 101, and the outer periphery of each elastic branch pipe 101 is provided. Shall always be in contact with air . In addition, if an underwater sound insulation structure as shown in FIG. 1 is used, the water supply device 2 and the circulation pipe 1 are connected by the elastic branch pipe 101, so that the mechanical vibration generated from the water supply apparatus 2 is transmitted to the circulation pipe 1. Can be prevented. The underwater sound insulation structure is used not only for the water supply section 10 but also for the water absorption section 13 of the circulating water tank because noise propagates in water regardless of the flow of water.

In the above-described embodiment, the case of installation in a circulating water tank has been described, but underwater (including other liquids).
Needless to say, the present invention can be applied to all cases in which it is necessary to isolate noise propagating in water.

[0012]

As described above, the underwater sound insulation structure according to the present invention enables the noise generated from the noise source itself, such as a water pump, to propagate through water under the noise source near the noise source. Therefore, when used in a circulating water tank used for measurement of a propeller or the like of a ship, it becomes possible to measure a small fluid noise that occurs when the propeller is at rest, for example. Further, since the water supply device and the circulating pipe are connected by the elastic branch pipe, there is an effect of having a vibration-proof effect of blocking transmission of vibration to the circulating pipe.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of an underwater sound insulation structure of the present invention.

FIG. 2 is a diagram for explaining this kind of conventional circulating water tank.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 circulation pipe 2 water supply device 3 measuring section 10 water supply section 11 rectifying section 12 elbow section 13 water absorption section 100 pressure-resistant reinforcing pipe 101 elastic branch pipe 102 reinforcing member

Continuation of the front page (72) Inventor Mutsumi Takashima 3-30 Kitashin, Seya-ku, Yokohama-shi, Kanagawa (56) References JP-A-10-10000 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , (DB name) G01M 10/00

Claims (2)

(57) [Claims] 1. An underwater sound insulation structure which is provided on a water absorption side or a water supply side (or on both a water absorption side and a water supply side) of a water supply device such as a pump, and which cuts off noise generated by the pump and propagated in water. When the upper limit of the wavelength in water underwater (sound speed is 1.5 km / sec; the same applies hereinafter) is λ, an acoustically soft pipe such as a rubber pipe having a diameter d of d ≦ λ / 1.3 is used. Reinforcing members are provided on the outer circumference of the formed branch pipes so that air does not intervene between them and they do not come into contact with each other, and are built in the required number of pressure-resistant reinforcing pipes determined from the amount of water supply per unit time. Underwater sound insulation structure. 2. A circulating water tank for use in measuring a propeller or the like of a ship, comprising the underwater sound insulation structure according to claim 1.