Method and system for measuring ship radiation sound in ship pool

Abstract

The invention provides a method for measuring ship radiation sound in a ship pool, which comprises the following steps of: constructing a double-layer envelope surface sound pressure measurement array in the ship pool, and establishing a ship radiation and pool wall reflection sound field model; establishing a sound field analysis model for inward and outward radiation of a semi-free space cylindrical surface, and constructing a semi-space double-cylindrical surface sound pressure-sound pressure transfer matrix; measuring the amplitude and phase of sound pressure according to the double envelope surfaces, and separating the radiated and reflected sound of the ship in the ship pool; a fixed hydrophone and two semicircular hydrophone linear arrays moving in the length direction of a ship are adopted, through equal-interval translation operation and reference phase calibration, the sound pressure of the whole double-layer cylindrical envelope surface is collected, time is used for replacing space, the complexity and economic cost of a system are effectively reduced, and the method is suitable for large-scale popularization and application. The method is especially suitable for engineering maintenance and cost control.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of underwater acoustics, in particular to a method and system for measuring ship radiated sound in a ship pool. BACKGROUND

[0002] The underwater radiated sound level of a warship is a core indicator for evaluating its acoustic stealth performance. The current mainstream sea measurement method has problems such as long deployment period, complex environmental noise interference (such as ocean turbulence, biological noise, shipping noise, etc.), and high support cost, which makes it difficult to meet the high-frequency and high-precision sound field evaluation requirements of ship design stage. In contrast, carrying out radiated sound measurement in a ship pool (semi-anechoic pool or special test pool) has the advantages of short test period, strong controllability of the environment (natural environmental noise can be isolated), and low cost, and has become a technical direction of attention for ship design units.

[0003] However, the sound reflection effect in the limited space of the ship pool causes the measured sound field to contain the superposition of ship radiated sound and pool wall reflected sound, and how to effectively separate the direct sound and the reflected sound is the core challenge of the ship pool measurement technology. The existing separation methods mainly have the following technical bottlenecks:

[0004] 1. Pulse method: relies on the time domain separability of radiated waves and reflected waves, and is only suitable for high frequency bands (when the wavelength is smaller than the distance between the sound source and the pool wall, there is a significant time difference between the direct wave and the reflected wave), but it is ineffective for low frequency radiated sound of warships (long wavelength, serious time domain aliasing);

[0005] 2. Ship pool Green function method: separate direct sound and reflected sound by constructing an integral equation of the sound field with boundary conditions, but its accuracy is highly dependent on the measurement accuracy of the pool wall complex reflection coefficient, and the reflection characteristics of the actual pool boundary (such as elastic wall surface, sound-absorbing coating) are affected by factors such as material parameters and frequency response, and the measurement error is difficult to control;

[0006] 3. Double-layer equivalent source method: based on double envelope surface pressure measurement data, the radiated sound field is inverted by an equivalent source model, but its separation accuracy is sensitive to the spatial distribution density of the equivalent source, the grid division strategy and other configuration parameters, and the calculation complexity is high and is easily disturbed by measurement noise.

[0007] In view of the above problems, it is urgent to break through the application limitations of traditional methods and develop a ship pool radiated sound field rapid measurement method with high efficiency, robustness and wide frequency applicability to meet the early evaluation and optimization requirements of the stealth performance of the ship design stage. SUMMARY

[0008] The present application aims at solving the above problems, and provides a ship pool ship radiation sound measurement method and system, which adopts a fixed hydrophone and two semi-circular ring hydrophone arrays moving along the length direction of the ship, realizes the collection of the sound pressure of the entire double-layer cylindrical envelope surface through the equal-interval translation operation and reference phase calibration, and effectively reduces the complexity and economic cost of the system by using time to replace space, and is especially suitable for engineering maintenance and cost control.

[0009] To achieve the above object, the present application adopts the following technical solutions.

[0010] A ship pool ship radiation sound measurement method, which comprises the following steps: constructing a ship pool double-layer envelope surface sound pressure measurement array, establishing a ship radiation and pool wall reflection sound field model; establishing a semi-free space cylindrical surface inward and outward radiation sound field analytical model, and constructing a semi-space double-cylindrical surface sound pressure-sound pressure transfer matrix; and separating the ship pool ship radiation and reflection sound according to the amplitude and phase of the double envelope surface measured sound pressure.

[0011] Further, the ship pool double-layer envelope surface sound pressure measurement array comprises a fixed hydrophone and two semi-circular ring hydrophone arrays with the axis located on the water surface and symmetrical about the ship.

[0012] Further, the distance between each array element of the semi-circular ring hydrophone array is less than one third of the wavelength of the upper limit analysis frequency.

[0013] Further, the semi-circular ring hydrophone array is horizontally moved along the axis direction.

[0014] Further, the moving distance between each time of the ship pool double-layer envelope surface sound pressure measurement array is less than one third of the wavelength of the upper limit analysis frequency.

[0015] Further, the array element collected signal is subjected to Fourier transform to obtain the sound pressure complex frequency spectrum, which comprises the inner envelope surface sound pressure and the outer envelope surface sound pressure.

[0016] Further, according to the sound field superposition principle, the inner envelope surface sound pressure and the outer envelope surface sound pressure are superimposed by the ship radiation sound pressure and the wall reflection sound pressure.

[0017] Further, according to the Helmholtz integral principle, the ship radiation sound pressure received by the outer envelope surface is uniquely determined by the ship radiation sound pressure received by the inner envelope surface, and the wall scattering sound pressure received by the inner envelope surface is uniquely determined by the wall scattering sound pressure received by the outer envelope surface, and the ship radiation sound pressure can be separated according to the sound pressure complex frequency spectrum measured by the inner and outer envelope surfaces and the double-layer envelope surface sound pressure-sound pressure transfer matrix.

[0018] A ship pool ship radiation sound measurement system, comprising a fixed hydrophone and a plurality of semi-circular ring hydrophone arrays, each array of the semi-circular ring hydrophone array has an array element spacing less than one-third of the wavelength of the upper limit analysis frequency, the semi-circular ring hydrophone array moves the array along the axial direction, and each time the semi-circular ring hydrophone array moves a distance less than one-third of the wavelength of the upper limit analysis frequency.

[0019] Further, comprising two semi-circular ring hydrophone arrays.

[0020] The positive effect of the ship pool ship radiation sound measurement method and system provided by the present application is:

[0021] (1) The present application designs a double-layer cylindrical envelope sound pressure measurement system specially used for separating ship pool ship low-frequency radiation sound and reflected sound. The system comprises a fixed hydrophone and two semi-circular ring hydrophone linear arrays moving along the length direction of the ship. Through equal-interval translation operation and reference phase calibration, the sound pressure of the entire double-layer cylindrical envelope surface is collected. Time is exchanged for space, which effectively reduces the complexity and economic cost of the system, and is especially suitable for engineering maintenance and cost control.

[0022] (2) The present application proposes a ship pool ship radiation sound and reflected sound separation method based on a double-layer cylindrical envelope surface sound pressure-sound pressure transfer matrix. The input data of the method is the sound pressure amplitude and phase obtained by measuring the double-layer envelope surface, that is, the superposition of radiation sound and reflected sound. The output result is the amplitude and phase of the radiation sound of the inner envelope surface. Compared with the traditional sound field separation technology, the present method is suitable for low frequency where the radiation wave and the reflected wave cannot be separated in time, does not need to measure the pool wall complex reflection coefficient and the ship pool environment Green function, and does not need to consider the influence of the equivalent source space configuration, significantly improves the separation precision of the radiation sound and the reflected sound, and greatly simplifies the evaluation process of the ship underwater radiation noise level.

[0023] (3) The present application can quickly and accurately separate the ship radiation sound and the pool wall reflected sound in the ship pool environment, avoiding the problems of low measurement efficiency and low frequency failure of the traditional method. It can be used for ship radiation noise source positioning, sound anomaly fault diagnosis and other applications. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a schematic diagram of a double semi-circular ring sound pressure measurement array provided by an embodiment of the present application.

[0025] Figure 2 is a schematic diagram of double cylindrical envelope surfaces formed in parallel provided by an embodiment of the present application.

[0026] Figure 3 is a schematic diagram of a double envelope surface sound pressure-sound pressure transfer matrix provided by an embodiment of the present application.

[0027] Figure 4 is a black-and-white diagram of a total sound pressure simulation result of a double-cylinder envelope surface in a ship pool environment according to an embodiment of the present application.

[0028] Figure 5 is a color diagram of a total sound pressure simulation result of a double-cylinder envelope surface in a ship pool environment according to an embodiment of the present application.

[0029] Figure 6 is a black-and-white diagram of a transfer matrix according to an embodiment of the present application.

[0030] Figure 7 is a color diagram of a transfer matrix according to an embodiment of the present application.

[0031] Figure 8 is a black-and-white diagram of a radiation sound separation result in a ship pool environment according to an embodiment of the present application.

[0032] Figure 9 is a color diagram of a radiation sound separation result in a ship pool environment according to an embodiment of the present application.

[0033] Figure 10 is a black-and-white diagram of an inner-side cylinder envelope surface radiation sound pressure without a pool wall according to an embodiment of the present application.

[0034] Figure 11 is a color diagram of an inner-side cylinder envelope surface radiation sound pressure without a pool wall according to an embodiment of the present application.

[0035] Figure 12 is a black-and-white diagram of a radiation sound curve varying with distance at different frequencies according to an embodiment of the present application.

[0036] Figure 13 is a color diagram of a radiation sound curve varying with distance at different frequencies according to an embodiment of the present application.

[0037] The reference numerals in the figures are as follows:

[0038] 1, fixed hydrophone; 2, semi-circular ring hydrophone array. DETAILED DESCRIPTION

[0039] The following will give a specific embodiment of a ship pool ship radiation sound measurement method and system according to the present application in combination with the accompanying drawings, but it is pointed out that the specific embodiment is not used to limit the specific implementation of the present application. Any similar structure and its similar changes that adopt the present application shall be included in the protection scope of the present application. The following embodiment description is with reference to the additional drawings to illustrate the specific embodiments that can be used to implement the present application. The formulas mentioned in the embodiment are used to explain and understand the present application, but not to limit the present application.

[0040] Reference is made to Figures 1-13A method for measuring ship radiated sound in a ship basin, comprising constructing a double-layered envelope surface sound pressure measuring array in the ship basin, establishing a ship radiated sound and basin wall reflected sound field model, establishing a semi-free space cylindrical surface inward and outward radiated sound field analytical model, constructing a semi-space double cylindrical surface sound pressure-sound pressure transfer matrix, and separating the ship radiated sound and reflected sound in the ship basin according to the amplitude and phase of the double envelope surface measured sound pressure.

[0041] The array element collected signals are subjected to Fourier transform to obtain sound pressure complex frequency spectrum, including inner envelope surface sound pressure and outer envelope surface sound pressure, according to the sound field superposition principle, the inner envelope surface sound pressure and the outer envelope surface sound pressure are superimposed by the ship radiated sound pressure and the wall reflected sound pressure, according to the Helmholtz integral principle, the ship radiated sound pressure received by the outer envelope surface is uniquely determined by the ship radiated sound pressure received by the inner envelope surface, and the wall scattered sound pressure received by the inner envelope surface is uniquely determined by the wall scattered sound pressure received by the outer envelope surface, and the ship radiated sound pressure can be separated according to the sound pressure complex frequency spectrum measured by the inner and outer envelope surfaces and the double-layered envelope surface sound pressure-sound pressure transfer matrix.

[0042] A ship radiated sound measuring system in a ship basin, comprising a fixed hydrophone 1 and a plurality of semicircular ring hydrophone arrays 2, each array element of the semicircular ring hydrophone array 2 has a spacing less than one third of the wavelength of the upper limit analysis frequency, the semicircular ring hydrophone array 2 moves the array along the axial direction, and each time the semicircular ring hydrophone array 2 moves a distance less than one third of the wavelength of the upper limit analysis frequency.

[0043] The technical solution is generally divided into three parts, one is to construct a double-layered envelope surface sound pressure measuring array in the ship basin, establish a ship radiated sound and basin wall reflected sound field model, two is to establish a semi-free space cylindrical surface inward and outward radiated sound field analytical model, construct a semi-space double cylindrical surface sound pressure-sound pressure transfer matrix, and three is to separate the ship radiated sound and reflected sound in the ship basin according to the amplitude and phase of the double envelope surface measured sound pressure.

[0044] A semicircular ring sound pressure measuring system in a ship basin, double cylindrical envelope surface sound pressure measurement and correction, ship radiated sound and reflected sound separation, double cylindrical surface sound pressure-sound pressure transfer matrix, and ship basin radiated sound and reflected sound field model.

[0045] 1. A double semicircular ring sound pressure measuring system in a ship basin

[0046] A fixed hydrophone 1 is suspended under the ship, and two semicircular ring hydrophone arrays 2 are deployed on the water surface, symmetric about the ship. The distance between each array element is less than one third of the wavelength of the upper limit of the analysis frequency. The array is moved horizontally along the axis direction, and the sound pressure of the double-layer cylindrical envelope is measured each time the moving distance is also less than one third of the wavelength of the upper limit of the analysis frequency.

[0047] The Fourier transform is performed on the signal collected by each array element to obtain the sound pressure complex frequency spectrum, wherein the sound pressures of the inner and outer envelope surfaces are denoted as and where f is the linear spectrum frequency of interest, and the output sound pressure of the fixed hydrophone 1 is normalized, that is, and

[0048] 2, Construct a ship pool radiation and reflection sound field model

[0049] According to the principle of sound field superposition, the sound pressures measured by the two envelope surfaces are superimposed by the ship radiation sound pressure p i (f) and the wall reflection sound pressure p s (f), that is,

[0050]

[0051] According to the Helmholtz integral principle, the ship radiation sound pressure received by the outer envelope surface is uniquely determined by the ship radiation sound pressure received by the inner envelope surface

[0052]

[0053] where G(r, r s ) is the Green function of the half-space free field

[0054]

[0055] Similarly, the wall scattering sound pressure received by the inner envelope surface is uniquely determined by the wall scattering sound pressure received by the outer envelope surface

[0056]

[0057] The following is obtained by combining them:

[0058]

[0059] where [T1] and [T2] are the sound pressure-sound pressure transfer matrices from the inner to the outer and from the outer to the inner, respectively. It can be seen that the ship radiation sound pressure or can be separated according to the sound pressure complex frequency spectrum measured by the inner and outer envelope surfaces and the sound pressure-sound pressure transfer matrix of the double-layer envelope surface.

[0060] 3, Double cylindrical surface sound pressure-sound pressure transfer matrix

[0061] The fast and robust calculation of the inner and outer envelope surface sound pressure-sound pressure transfer matrices [T1] and [T2] is the key to the separation of the radiated sound and the reflected sound from the wall surface of the ship pool.

[0062] The physical meaning of the inner-to-outer envelope surface sound pressure-sound pressure transfer matrix [T1] is that the outer cylinder receives the sound pressure when the inner cylinder radiates outward and the sound pressure of the current area (satisfying far less than the wavelength of the sound wave) is 1 and the sound pressure of other areas is 0. In the case of far less than the wavelength of the sound wave, the area is related to the area and is not sensitive to the shape. In order to simplify the analysis, it is approximated to a rectangle with two edges parallel to the z-axis.

[0063] The cylindrical coordinate system is established with the axis of the cylinder as the z-axis, the free liquid surface is located at θ = 0° and θ = 180°, and the inner and outer cylinder surfaces are located at r = a and r = b. Without loss of generality, let the center coordinate of the radiation surface be (a, θ1, 0), the height be 2z0, and the angle be 2θ0. The observation point coordinate is (b, θ2, z2-z1).

[0064] Figure 3 In the above, the left side is [T1] and the right side is [T2].

[0065] In the cylindrical coordinate system, the general solution form of the sound field is:

[0066]

[0067] where

[0068]

[0069] The expansion coefficients can be determined using the orthogonality, i.e.

[0070]

[0071] The expansion coefficients can be determined using the orthogonality, i.e.

[0072]

[0073] Substituting equation (6) can obtain the elements of the transfer matrix [T1].

[0074] The outer-to-inner envelope surface sound pressure-sound pressure transfer matrix [T2] has the physical meaning that the inner cylinder receives the sound pressure when the outer cylinder radiates inward and the sound pressure of the current area is 1 and the sound pressure of other areas is 0. The general solution form of the sound field is:

[0075]

[0076] According to the orthogonality (8), the expansion coefficients can be determined.

[0077]

[0078] Substitute equation (10) can be obtained by the transfer matrix [T2] each element.

[0079] Substitute equation (5), namely the inner envelope surface radiation sound.

[0080] Example 1: using the method of the patent, the ship pool environment under the cylindrical shell cabin section radiation sound field is analyzed, the input is the total sound pressure simulation results of double cylindrical envelope surface, see Figure 4 And Figure 5 The upper one in the figure is the 50Hz, ship pool environment P1 surface sound field distribution; the lower one in the figure is the 50Hz, ship pool environment P2 surface sound field distribution.

[0081] According to equation (6), (10), the inner and outer envelope surface sound pressure-sound pressure transfer matrix [T1], [T2], Figures 6-7 , in the figure, the upper one is the inner envelope surface sound pressure-sound pressure transfer matrix [T1], and the lower one is the outer envelope surface sound pressure-sound pressure transfer matrix [T2].

[0082] According to equation (5), the inner cylindrical envelope surface radiation sound ( Figures 8-9 ) is separated and compared with the radiation sound without pool wall ( Figures 10-11 ). It can be seen that the method can accurately separate the ship radiation sound in the ship pool.

[0083] Figures 12-13 Compare the results of the radiation sound separated by the method proposed in the patent, the equivalent source method and the simulation results of the radiation sound without pool wall, the frequency is 50Hz, 60Hz and 80Hz respectively. Select the water depth of 3m in the ship pool, calculate the radiation sound pressure level in the range of-4m to 4m. The left side of the figure from top to bottom is the result of the patent at 50Hz, 60Hz and 80Hz respectively. The blue line in the left 1 figure is the calculation result of the semi-infinite space (the upper line), the red line is the unseparated result of the harbor pool (the lower line), and the red dotted line is the separated calculation result of the harbor pool. The right side of the figure from top to bottom is the result of the equivalent source at 50Hz, 60Hz and 80Hz respectively.

[0084] It can be seen that the radiation sound separation result of the equivalent source at some frequencies is very large, which is caused by the spatial configuration of the equivalent source; in contrast, the radiation sound separation result of the method proposed in the patent always agrees well with the result without pool wall.

Claims

1. A method for measuring radiated sound from a ship in a ship basin, characterized in that: This includes constructing a double-layer envelope surface sound pressure measurement array in the ship pool, establishing a ship radiation and pool wall reflection sound field model; establishing an analytical model of the inward and outward radiation sound field of a semi-free space cylinder, and constructing a half-space double-cylinder sound pressure-sound pressure transfer matrix; The amplitude and phase of the sound pressure are measured by the double envelope surface to separate the radiated and reflected sound of the ship in the tank.

2. The method for measuring radiated sound of a ship in a ship basin according to claim 1, characterized in that: The double-layer envelope surface sound pressure measurement array in the ship pool includes a fixed hydrophone and a semi-circular hydrophone array with two axes located on the water surface and symmetrical about the ship.

3. The method for measuring radiated sound of a ship in a ship basin according to claim 2, characterized in that: The spacing between each array element of the semicircular hydrophone array is less than one third of the wavelength of the upper limit analysis frequency.

4. The method for measuring radiated sound of a ship in a ship basin according to claim 3, characterized in that: The semicircular hydrophone array is moved horizontally along the axis direction.

5. The method for measuring radiated sound of a ship in a ship basin according to claim 4, characterized in that: The distance between each movement of the double-layer envelope surface sound pressure measurement array in the boat pool is less than one third of the wavelength of the upper limit analysis frequency.

6. The method for measuring radiated sound of a ship in a ship basin according to claim 5, characterized in that: The array element collects the signal and performs Fourier transform to obtain a complex spectrum of sound pressure, including the sound pressure of the inner envelope surface and the sound pressure of the outer envelope surface.

7. The method for measuring radiated sound of a ship in a ship basin according to claim 6, characterized in that: According to the principle of sound field superposition, the sound pressure on the inner envelope surface and the sound pressure on the outer envelope surface are the superposition of the ship radiation sound pressure and the wall reflection sound pressure.

8. The method for measuring radiated sound of a ship in a ship basin according to claim 7, characterized in that: According to the Helmholtz integral principle, the ship radiation sound pressure received by the outer envelope surface is uniquely determined by the ship radiation sound pressure received by the inner envelope surface, and the wall scattered sound pressure received by the inner envelope surface is uniquely determined by the wall scattered sound pressure received by the outer envelope surface. The ship radiation sound pressure can be separated based on the sound pressure complex spectra measured by the inner and outer envelope surfaces and the double-layer envelope surface sound pressure-sound pressure transfer matrix.

9. A ship radiated sound measurement system in a ship basin, characterized in that: The invention comprises a fixed hydrophone and a plurality of semicircular hydrophone arrays, wherein the spacing between each array element of the semicircular hydrophone array is less than one-third of the wavelength of the upper limit analysis frequency. The semicircular hydrophone array is horizontally movable along the axis direction, and the distance between each movement of the semicircular hydrophone array is less than one-third of the wavelength of the upper limit analysis frequency.

10. The ship radiated sound measurement system in a ship basin according to claim 9, characterized in that: It consists of two semicircular hydrophone arrays.

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