Method and system for measuring omnidirectional sound source very low frequency radiated sound power in a reverberation tank

Abstract

The present application belongs to the technical field of underwater sound source radiation characteristic measurement, and relates to a method and system for measuring the very low frequency radiation sound power of an omnidirectional sound source in a reverberation tank. The method comprises: determining the first-order resonance frequency according to the structural parameters and water level of the reverberation tank; placing a standard sound source at the center of the tank and arranging multiple hydrophones at intervals on one side of the sound source; exciting the standard sound source to emit sound with a single-frequency continuous sinusoidal signal lower than the first-order resonance frequency, establishing a standard sound pressure field fitting model based on the radiation sound pressure amplitude collected by the hydrophones, and solving the exponential function adjustment factor and the standard sound source intensity factor; replacing the standard sound source with the sound source to be measured, exciting the sound source to emit sound with the same single-frequency continuous sinusoidal signal, establishing a sound pressure field fitting model for the sound source to be measured based on the radiation sound pressure amplitude collected by the hydrophones, and solving the intensity factor of the sound source to be measured; and calculating the radiation sound power of the sound source to be measured. The present application realizes the rapid and accurate acquisition of the very low frequency radiation sound power of the sound source to be measured.

Description

Technical Field

[0001] This invention belongs to the field of underwater sound source radiation characteristic measurement technology, specifically relating to a method and system for measuring the very low frequency radiated sound power of an omnidirectional sound source in a reverberant pool. Background Technology

[0002] The radiated acoustic power of an underwater sound source is a core acoustic parameter that quantitatively describes the intensity and propagation capability of underwater sound energy radiation. Its accurate measurement is a prerequisite for underwater target detection and identification, and also a technical means to objectively evaluate the effectiveness of underwater target vibration reduction and noise reduction, which has important engineering application value.

[0003] Traditional methods for measuring the radiated sound power of underwater sound sources are based on free-field environments and are generally implemented using anechoic tanks or open water. However, anechoic tanks are expensive and have limited performance in the low-frequency range; while measurements in open water cannot avoid the significant impact of external environmental factors such as wind and waves on measurement repeatability. Therefore, traditional measurement methods are difficult to accurately obtain the low-frequency and very low-frequency radiated sound power of underwater sound sources in practical applications. In contrast, obtaining the radiated sound power of underwater sound sources in reverberation tanks has significant advantages such as low background noise, high measurement accuracy, and good measurement repeatability. In recent years, various measurement methods based on reverberation tanks have emerged and been widely used.

[0004] Chinese scholar Li Qi first proposed using spatial moving average technology to measure the sound field of a reverberant water tank, and combined with the reverberation time, the radiated sound power of the sound source could be calculated (Li Qi. Research on Noise Measurement Method of Water Tank [D]. Harbin: Harbin Shipbuilding Engineering Institute, 1990). Based on this, Shang Dajing proposed using the reverberation method to measure the radiated sound power of complex structure sound sources in a reverberant water tank (Shang Dajing, Li Qi, Shang Dejiang. Experimental Study on Measurement of Radiated Sound Power of Underwater Sound Source [J]. Journal of Harbin Engineering University, 2010, 31(07):938-944). However, this method is only applicable to the frequency band above the lower limit frequency of the reverberant sound field and does not extend the application frequency domain of the reverberant water tank to lower frequency bands. Subsequently, Chinese patent CN104501938B proposed a method for measuring the low-frequency radiated sound power of an underwater sound source in a rectangular reverberant water tank placed in the air. This method is based on normal mode theory and successfully extends the measurable frequency of the reverberant water tank to the frequency band between the lower limit frequency of the reverberant sound field and the first-order resonance frequency. However, when the test frequency is lower than the first-order resonance frequency of the reverberant sound field, there are no normal modes that can be excited in the sound field, and the above method is no longer applicable. Subsequently, Chinese patent CN109916497B proposed a method for measuring the very low frequency radiation characteristics of underwater sound sources in a reverberant tank. This method uses a sound intensity probe composed of two hydrophones to measure the sound pressure and normal particle velocity on a selected envelope surface and performs sound energy flow separation to obtain the radiated sound power of the target. This overcomes the measurement bottleneck of the reverberant tank sound field in the frequency band below the first-order resonant frequency. However, this method still has the following limitations in practical applications: 1) The reverberant sound field is formed by the superposition of direct and reflected waves. When using two hydrophones to obtain the normal particle velocity, a large deviation will occur due to the influence of the reflected wave; 2) The calculation process of near-field sound energy flow separation is based on the phase difference between the sound pressure and the normal particle velocity, which requires extremely high phase consistency of the two hydrophones, which is often difficult to achieve in reality, thus leading to a decrease in measurement accuracy. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method and system for measuring the very low frequency radiated sound power of an omnidirectional sound source in a reverberant water tank. The aim is to overcome the deficiencies mentioned in the background art regarding the measurement of the radiation characteristics of existing underwater sound sources, and to improve the measurement accuracy and efficiency of the low-frequency and very low-frequency radiated sound power of omnidirectional sound sources.

[0006] This invention provides a method for measuring the very low frequency radiated sound power of an omnidirectional sound source in a reverberant water tank, comprising the following steps: S1. Based on the structural parameters of the reverberation tank and the loading water level, determine the first-order resonant frequency and the maximum measurable volume of the underwater sound source; the reverberation tank is a rectangular tank, and the center of the length, width and water depth of the reverberation tank is defined as the center of the sound source. S2. Place a standard sound source in a reverberation pool and position the equivalent sound center of the standard sound source at the center of the sound source. On one side of the sound source center, along the central axis of the width of the reverberation pool at the same height as the sound source center, arrange multiple hydrophones at intervals to form a hydrophone array. S3. Using a single-frequency continuous sinusoidal signal lower than the first-order resonant frequency as the input to the standard sound source, the standard sound source is excited to emit sound. The radiated sound pressure amplitude of the standard sound source is collected using all hydrophones, and the standard sound source radiated sound pressure field fitting model shown in equation (3) is established; where, This is the serial number of the hydrophone. , The number of hydrophones; For the first The distance between the hydrophone and the center of the sound source For the first The standard sound source radiated sound pressure amplitude was collected by a hydrophone; the exponential function adjustment factor was calculated using the least squares method. and standard sound source intensity factor ; (3); S4. Replace the standard sound source with the sound source to be tested, and excite the sound source to be tested with the same single-frequency continuous sinusoidal signal as in step S3. Use all hydrophones to collect the radiated sound pressure amplitude of the sound source to be tested, and establish the radiated sound pressure field fitting model of the sound source to be tested as shown in equation (18); where... For the first The sound pressure amplitude of the sound source under test was collected by a hydrophone; the intensity factor of the sound source under test was calculated using the least squares method. ; (18); S5. Calculate the radiated sound power of the sound source under test according to equation (27). ;in, The radiated sound power of a standard sound source; (27).

[0007] In some embodiments, in step S1, the first-order resonant frequency The calculation is performed according to equation (1), where, The speed of sound in water, The length of the reverberation pool For the width of the reverberation pool, The water level in the reverberation tank; (1).

[0008] In some embodiments, in step S1, the maximum measurable volume of the underwater sound source is determined. Calculate according to formula (2); (2).

[0009] In some embodiments, the net distance between the hydrophone closest to the center of the sound source and the standard sound source or the sound source to be tested is greater than a preset threshold. The preset threshold is determined based on the maximum horizontal scale of the standard sound source and the sound source to be tested. The distance between any two adjacent hydrophones is less than one-eighth of the wavelength of the first resonant frequency.

[0010] In some embodiments, when a standard sound source or a sound source under test is excited to emit sound with a single-frequency continuous sinusoidal signal, the amplitude of the signal input is adjusted so that the measured signal-to-noise ratio is not less than 6dB.

[0011] In some embodiments, in step S3, the exponential function adjustment factor The standard sound source intensity factor is calculated according to equation (14). The solution is performed according to equation (15); where, The mean distance between the hydrophone and the center of the sound source is calculated according to equation (16); The logarithmic mean of the radiated sound pressure amplitude of the standard sound source is calculated according to equation (17); (14); (15); (16); (17).

[0012] In some embodiments, in step S4, the intensity factor of the sound source to be measured is... The solution is performed according to equation (25); where, The logarithmic mean of the amplitude of the radiated sound pressure from the sound source under test is calculated according to equation (26); (25); (26).

[0013] In some embodiments, step S5 further includes calculating the radiated sound power level of the sound source under test according to equation (28). ;in, This is a reference value for the radiated sound power level; (28).

[0014] This invention also provides a system for measuring the very low frequency radiated sound power of an omnidirectional sound source in a reverberant water tank, used to perform the aforementioned method for measuring the very low frequency radiated sound power of an omnidirectional sound source in a reverberant water tank. The system for measuring the very low frequency radiated sound power of an omnidirectional sound source in a reverberant water tank includes: The acquisition module is used to excite the standard sound source and the sound source under test to emit sound, and to acquire the radiated sound pressure amplitude data of the standard sound source and the sound source under test. The fitting module is used to establish a fitting model of the standard sound source radiation sound pressure field based on the standard sound source radiation sound pressure amplitude collected by all hydrophones and the distance between the hydrophone and the sound source center, and then use the least squares method to calculate the exponential function adjustment factor and the standard sound source intensity factor; it is also used to establish a fitting model of the sound source radiation sound pressure field to be tested based on the sound source radiation sound pressure amplitude collected by all hydrophones and the distance between the hydrophone and the sound source center, and then use the least squares method to calculate the sound source intensity factor to be tested; The output module is used to calculate and output the radiated sound power of the sound source under test based on the standard sound source intensity factor, the sound source intensity factor under test, and the standard sound source radiated sound power.

[0015] Based on the above technical solution, the method and system for measuring the very low frequency radiated sound power of an omnidirectional sound source in a reverberant water tank in this invention avoids the stringent requirements of existing methods that require accurate acquisition of the field point sound pressure, complex particle velocity, and the phase difference between the two. By measuring the single variable of the field point radiated sound pressure amplitude, the method achieves rapid and accurate acquisition of the very low frequency radiated sound power of the sound source under test, significantly improving measurement accuracy and efficiency. It is suitable for rapid and accurate calibration of the low frequency and very low frequency radiated sound power of omnidirectional underwater acoustic transducers. Attached Figure Description

[0016] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a flowchart of the method for measuring the very low frequency radiated sound power of an omnidirectional sound source in a reverberant water tank according to the present invention. Figure 2 This is a diagram showing the arrangement of the sound source and hydrophone array in the reverberation tank of the present invention. Figure 3 To determine the input signal frequency of the standard sound source and the sound source under test in the reverberation tank. The fitted graph shows the radiated sound pressure field data at 150Hz. Figure 4 To determine the input signal frequency of the standard sound source and the sound source under test in the reverberation tank. The fitted graph shows the radiated sound pressure field data at 300Hz. Figure 5To determine the input signal frequency of the standard sound source and the sound source under test in the reverberation tank. The fitted graph shows the radiated sound pressure field data at 450 Hz. Figure 6 To determine the input signal frequency of the standard sound source and the sound source under test in the reverberation tank. The fitted graph shows the radiated sound pressure field data at 600Hz. Figure 7 To determine the input signal frequency of the standard sound source and the sound source under test in the reverberation tank. The fitted graph shows the radiated sound pressure field data at 750 Hz. Figure 8 To determine the input signal frequency of the standard sound source and the sound source under test in the reverberation tank. The fitted graph shows the radiated sound pressure field data at 900Hz. Figure 9 To determine the input signal frequency of the standard sound source and the sound source under test in the reverberation tank. The fitted graph shows the radiated sound pressure field data at 1050 Hz. Figure 10 This is a comparison graph showing the very low frequency radiated sound power level of the sound source under test obtained by existing methods and the method of the present invention in a reverberation tank, and the theoretical value. Detailed Implementation

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0018] In the description of this invention, it should be understood that the terms "center", "lateral", "longitudinal", "upper", "lower", "top", "bottom", "inner", "outer", "left", "right", "front", "rear", "vertical", "horizontal", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0019] The terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature.

[0020] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0021] refer to Figures 1-2 As shown, this invention provides a method for measuring the very low frequency radiated sound power of an omnidirectional sound source in a reverberant water tank, used to measure the low-frequency and very low-frequency radiated sound power of an omnidirectional sound source in a reverberant water tank. The method includes the following steps S1 to S5.

[0022] Step S1: Determine the first-order resonant frequency and the maximum measurable volume of the underwater sound source based on the structural parameters of the reverberation tank and the water level. The reverberation tank is a rectangular tank, and the center of the reverberation tank in the length, width, and water depth directions is defined as the center of the sound source.

[0023] Specifically, the first-order resonant frequency According to equation (1), the first-order resonant frequency is the first-order natural resonant frequency; where, The speed of sound in water, The length of the reverberation pool For the width of the reverberation pool, The water level in the reverberation tank is the height of the water surface from the bottom of the tank; through... The calculations determined the first-order resonant frequency, thereby clarifying the effective measurement frequency range (i.e., 0~) for measuring the low-frequency and very low-frequency radiated sound power of underwater sound sources in the reverberation pool. ); (1).

[0024] Furthermore, the maximum measurable volume of underwater sound sources Calculations are performed according to equation (2); through The calculation limits the maximum volume of the standard sound source and the sound source under test used subsequently. (2).

[0025] Step S2: Place a standard sound source in the reverberation pool, and ensure that the equivalent sound center of the standard sound source is located at the defined sound source center of the reverberation pool; on one side of the sound source center, along the central axis of the width of the reverberation pool at the same height as the sound source center, arrange multiple hydrophones at intervals to form a hydrophone array; that is, all hydrophones are arranged in half of the space along the length of the reverberation pool, and all hydrophones are located at the same water depth as the equivalent sound center of the standard sound source, and multiple hydrophones are arranged at intervals along the length of the reverberation pool and located on the central axis of the width of the reverberation pool.

[0026] To further clarify, the net distance (i.e., the distance between the hydrophone and the surface of the sound source) between the hydrophone closest to the center of the sound source and the standard sound source or subsequent sound source under test is greater than a preset threshold. The preset threshold is determined based on the largest horizontal dimension of the standard sound source and the subsequent sound source under test, i.e., the larger of the two values. The distance between any two adjacent hydrophones is less than the first-order resonant frequency. One-eighth of the wavelength; the method of calculating the wavelength based on the frequency is well known to those skilled in the art; when an underwater sound source emits sound, a sound field is excited in the reverberation pool, and the location of the hydrophone is the sound field observation point.

[0027] Step S3, at a frequency lower than the first-order resonant frequency A single-frequency continuous sinusoidal signal is used as the input to a standard sound source to excite it to emit sound. It can be understood that frequencies below the first-order resonant frequency are considered low frequencies and very low frequencies. After the standard sound source has stabilized, the radiated sound pressure amplitude of the standard sound source is collected using all hydrophones. , This is the serial number of the hydrophone. , The number of hydrophones; it is understood that when a standard sound source is excited by a single-frequency continuous sinusoidal signal, the signal input amplitude is adjusted to ensure that the measured signal-to-noise ratio is not less than 6dB, so as to suppress the influence of environmental noise on the radiated sound pressure amplitude data and ensure the accuracy of the collected data.

[0028] Furthermore, a fitting model for the standard sound source radiated sound pressure field, as shown in equation (3), is established; where, For the first The distance between the hydrophone and the center of the sound source For the first The standard sound source radiated sound pressure amplitude collected by a hydrophone. The standard sound source intensity factor, It is an exponential function adjustment factor. It is only related to the dimensional parameters of the reverberation tank and the measurement frequency; (3).

[0029] The adjustment factor of the exponential function is calculated using the least squares method. and standard sound source intensity factor Specifically, it includes the following steps S31 to S34.

[0030] Step S31: Linearize the fitting model of the standard sound source radiated sound pressure field; take the natural logarithm of both sides of equation (3) to transform equation (3) into equation (4), and let , Then we get the standard linear model of the standard sound source radiation sound pressure field fitting model shown in equation (5); (4); (5); Step S32: Set the least squares objective as shown in equation (6) That is, construct the sum of squared residuals and minimize it; respectively for and Find the partial derivatives and set the derivatives to 0, which are expressed as equations (7) and (8); (6); (7); (8); Step S33: Rearrange equations (7) and (8) to obtain the normal equation system shown in equation (9); (9); From the first equation in equation (9), we can obtain the equation shown in equation (10). The expression, where, for indivual The mean, for indivual The mean; Substituting into the second equation in equation (9), we can obtain the expression shown in equation (11); (10); (11); Based on the standard linear model shown in equation (5), the deviation and sum are defined. , This can be expressed as equation (12); thus, the expression in equation (11) can be... Represented as equation (13); (12); (13); Step S34: Substitute equation (12) into equation (13) and combine... The exponential function adjustment factor shown in equation (14) is obtained. The solution formula; the formula shown in equation (10) Substitution In this process, the standard sound source intensity factor shown in equation (15) is obtained. The solution formula; where, The mean distance between the hydrophone and the center of the sound source is calculated according to equation (16); The logarithmic mean of the radiated sound pressure amplitude of the standard sound source is calculated according to equation (17); (14); (15); (16); (17).

[0031] Therefore, the standard sound source is measured at a frequency of The corresponding dataset Substituting these values ​​into equations (14) to (17), the exponential function adjustment factor can be calculated. and standard sound source intensity factor .

[0032] Step S4: Keeping all parameters of the reverberation tank and the placement of the hydrophone array unchanged, replace the standard sound source with the sound source to be tested, ensuring that the equivalent sound center of the sound source to be tested is also located at the defined center of the reverberation tank sound source; use the same frequency as in step S3. A single-frequency continuous sinusoidal signal is used as the input to the sound source under test to excite it to emit sound. Simultaneously, the signal input amplitude is adjusted to ensure the measured signal-to-noise ratio is not less than 6 dB. After the sound source under test stabilizes, all hydrophones are used to collect the radiated sound pressure amplitude of the sound source. , This is the serial number of the hydrophone.

[0033] Furthermore, a fitting model for the radiated sound pressure field of the sound source under test, as shown in equation (18), is established; wherein, For the first The distance between the hydrophone and the center of the sound source For the first The amplitude of the radiated sound pressure from the sound source under test, collected by a hydrophone. The intensity factor of the sound source to be measured is... This is the adjustment factor for the exponential function (already obtained through step S3); (18); The intensity factor of the sound source under test is calculated using the least squares method. Specifically, it includes the following steps S41 to S43.

[0034] Step S41: Linearize the fitting model of the radiated sound pressure field of the sound source to be tested; take the natural logarithm of both sides of equation (18) to transform equation (18) into equation (19), and let , Then, the standard linear model of the sound pressure field fitting model of the sound source under test, as shown in equation (20), is obtained. (19); (20); Step S42: Set the least squares objective as shown in equation (21) That is, constructing the sum of squared residuals and minimizing it; for Find the partial derivative and set the derivative = 0, which is expressed as equation (22); (twenty one); (twenty two); Rearranging equation (22) yields the normal equation shown in equation (23), which, when transformed, yields the equation shown in equation (24). The expression; where, for indivual The mean, for indivual The mean; (twenty three); (twenty four); Step S43, as shown in equation (24) Substitution In the process, the intensity factor of the sound source to be measured, as shown in equation (25), is obtained. The solution formula; where, The mean distance between the hydrophone and the center of the sound source is calculated according to equation (16); The logarithmic mean of the amplitude of the radiated sound pressure from the sound source under test is calculated according to equation (26); (25); (26).

[0035] Therefore, the sound source to be tested is at a measurement frequency of The corresponding dataset and exponential function adjustment factor Substituting these values ​​into equations (25), (26), and (16), the intensity factor of the sound source to be measured can be calculated. .

[0036] Step S5: Calculate the radiated sound power of the sound source under test according to equation (27). ;in, The radiated sound power of the standard sound source is known. (27).

[0037] Furthermore, in the field of underwater acoustics, radiated sound power is usually expressed in units of 2000 (B), i.e., radiated sound power level. Therefore, the radiated sound power level of the sound source under test can be calculated according to equation (28). ;in, The reference value for the radiated sound power level is 0.67 x 10⁻⁶. -18 W; (28).

[0038] The above illustrative embodiment, by placing the sound source at the center of a rectangular reverberation pool, can excite a fully symmetrical sound field distribution. Based on this, placing the hydrophone array only in half of the space along the length of the reverberation pool can avoid the influence of reflected waves from half of the pool wall, which is beneficial to improving measurement accuracy. Moreover, compared with the stringent requirements of existing methods that require obtaining the field point sound pressure, complex particle velocity, and the phase difference between the two, this embodiment can achieve rapid and accurate acquisition of the low-frequency and very low-frequency radiated sound power of the sound source under test by only collecting the single variable of the field point radiated sound pressure amplitude.

[0039] This invention also provides a system for measuring the very low frequency (VLF) radiated sound power of an omnidirectional sound source in a reverberation tank, used to perform the aforementioned method for measuring the VLF radiated sound power of an omnidirectional sound source in a reverberation tank. The system includes an acquisition module, a fitting module, and an output module. The acquisition module is used to excite a standard sound source and the sound source under test to emit sound, and to acquire the radiated sound pressure amplitude data of the standard sound source and the sound source under test. The fitting module is used to establish a fitting model of the standard sound source radiated sound pressure field based on the standard sound source radiated sound pressure amplitude acquired by all hydrophones and the distance between the hydrophone and the center of the sound source, and then uses the least squares method to calculate the exponential function adjustment factor and the standard sound source intensity factor. The fitting module is also used to establish a fitting model of the sound source radiated sound pressure field of the sound source under test based on the sound pressure amplitude acquired by all hydrophones and the distance between the hydrophone and the center of the sound source, and then uses the least squares method to calculate the intensity factor of the sound source under test. The output module is used to calculate and output the radiated sound power of the sound source under test based on the standard sound source intensity factor, the sound source intensity factor under test, and the standard sound source radiated sound power.

[0040] refer to Figures 1-9 As shown, the main process of measuring the very low frequency radiated sound power of a cylindrical sound source using this invention is briefly described below: (1) The reverberation tank is a rectangular tank, and its structural parameters include length. It is 1.8m wide 0.9m, loading water level height The velocity of sound in water is 0.8m; the corresponding velocity of sound in water at a temperature of 25℃. The radiated sound power is 1497 m / s. A spherical sound source is used as the standard sound source. The radius of the spherical sound source is 0.07 m, the surface normal vibration velocity is 0.002 m / s, and its radiated sound power is known. The sound source to be tested is a cylindrical sound source. The base radius of the sound source is 0.06 m, the height is 0.10 m, and the surface normal vibration velocity is 0.006 m / s. Both the spherical sound source and the cylindrical sound source used are omnidirectional sound sources.

[0041] Using step S1 of this invention, the first-order resonant frequency is calculated according to equation (1). The effective measurement frequency range for measuring the very low frequency radiated sound power of an underwater sound source in the reverberation pool is 0–1319 Hz, thus clarifying that the effective measurement frequency range is 0–1319 Hz. The maximum measurable volume of the underwater sound source is calculated according to equation (2). It is 0.013m 3 Verification has shown that the spherical and cylindrical sound sources meet the maximum volume requirement.

[0042] (2) Using step S2 of the present invention, the spherical sound source is placed at the center of the sound source in the reverberation pool, and 11 hydrophones are arranged at intervals on one side of the spherical sound source and on the central axis of the width of the reverberation pool at the same height as the center of the sound source to form a hydrophone array; the distance between the hydrophone closest to the center of the sound source and the center of the sound source is 0.3m, and the net distance between the hydrophone and the spherical sound source is 0.23m; based on the maximum horizontal dimensions of the spherical sound source and the cylindrical sound source, the preset threshold can be determined to be 0.14m. Since 0.23m > 0.14m, it can be seen that the placement of the hydrophone closest to the center of the sound source meets the requirements; the distance between any two adjacent hydrophones is 0.05m, and it can be seen that the distance between the hydrophone furthest from the center of the sound source and the center of the sound source is 0.8m.

[0043] (3) Using step S3 of the present invention, within the determined effective measurement frequency range of 0 to 1319 Hz, select a frequency. A set of single-frequency continuous sinusoidal signals of Hz is used as input to a spherical sound source to excite the spherical sound source to produce sound, and the sound pressure amplitude of the spherical sound source collected by all hydrophones at each frequency is obtained. , ;Will Distance between the hydrophone and the center of the sound source By combining these methods, a fitting model for the radiated sound pressure field of a spherical sound source is established. The exponential function adjustment factor at each frequency is calculated using the least squares method. and standard sound source intensity factor .

[0044] (4) Using step S4 of the present invention, replace the spherical sound source with the cylindrical sound source to be tested, and make the equivalent sound center of the cylindrical sound source also located at the sound source center of the reverberation pool; select a single-frequency continuous sinusoidal signal with the same frequency as in step S3 as the input of the cylindrical sound source, and obtain the sound pressure amplitude data of the cylindrical sound source collected by all hydrophones at each frequency. ;Will and By combining these methods, a fitting model for the radiated sound pressure field of a cylindrical sound source is established. The intensity factor of the sound source at each frequency was calculated using the least squares method. .

[0045] (5) Using step S5 in this invention, the radiated sound power of the cylindrical sound source at each frequency is calculated according to equation (27). Then, the radiated sound power level of the cylindrical sound source at each frequency is calculated according to equation (28). Due to space limitations, only frequency is considered. The relevant data is shown in Table 1, taking Hz as an example.

[0046] Table 1: Frequency of Sound Source Input Signal Data at 1050Hz

[0047] To illustrate the technical effect of this invention, based on the same reverberation tank, the very low frequency radiated sound power level of the cylindrical sound source was measured using existing methods. Specifically, a spherical closed measurement envelope was added at a set distance (e.g., 0.25m) from the equivalent sound center of the cylindrical sound source, and near-field acoustic energy flow separation and free-field correction of the radiated acoustic energy components were performed on the cylindrical sound source according to existing methods (Chinese Patent CN109916497B), ultimately obtaining the very low frequency radiated sound power level of the cylindrical sound source. The measurement results of the existing method are summarized and compared with the measurement results and theoretical values ​​of the method of this invention, as shown in Table 2 and... Figure 10 As shown; it should be noted that the theoretical value of the very low frequency radiated sound power level of the cylindrical sound source is the radiated sound power level under an ideal non-reflection sound field environment obtained by multiphysics simulation software.

[0048] Table 2: Measurement results and theoretical values ​​of the very low frequency radiated sound power level of a cylindrical sound source obtained in a reverberant water tank using existing methods and the method of the present invention.

[0049] As can be seen from the above comparison, compared with the existing methods, the very low frequency radiated sound power level of the cylindrical sound source obtained by the method of the present invention has a very good consistency with the theoretical value; thus proving that the present invention can significantly improve the measurement accuracy of the very low frequency radiated sound power of underwater sound sources in a reverberant pool.

[0050] Through the description of several embodiments of the method and system for measuring the very low frequency radiated sound power of an omnidirectional sound source in a reverberant water tank according to the present invention, it can be seen that the present invention has at least one or more of the following advantages: 1) By placing the sound source at the center of the rectangular reverberation pool, the present invention can excite a fully symmetrical sound field distribution. On this basis, the hydrophone array is placed only in half of the space along the length of the reverberation pool, which can avoid the influence of reflected waves from half of the pool wall and improve measurement accuracy. 2) This invention targets the frequency band below the first-order resonant frequency of a reverberant water tank, avoiding the stringent requirements of existing methods that require accurate acquisition of the complex sound pressure, complex particle velocity, and phase difference between the two at the field point. By measuring the amplitude of the radiated sound pressure at the field point as a single variable, it achieves rapid and accurate acquisition of the very low frequency radiated sound power of the sound source under test, significantly improving the measurement accuracy and efficiency of the low-frequency and very low-frequency radiated sound power of omnidirectional sound sources. It is especially suitable for the rapid and accurate calibration of the low-frequency and very low-frequency radiated sound power of omnidirectional underwater acoustic transducers. 3) Standard sound source related parameters in this invention (such as exponential function adjustment factor) Standard sound source intensity factor Radiated sound power of a standard sound source Only a single measurement and calculation is required, and the data can be directly retrieved for subsequent measurements of other sound sources under test, greatly improving the measurement and calibration efficiency of low-frequency and very low-frequency radiated sound power of sound sources under test, such as underwater transducers.

[0051] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0052] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A method for measuring the very low frequency radiated sound power of an omnidirectional sound source in a reverberant water tank, characterized in that, Includes the following steps: S1. Determine the first-order resonant frequency and the maximum measurable volume of the underwater sound source based on the structural parameters of the reverberation pool and the loading water level. The reverberation pool is a rectangular pool, and the center of the reverberation pool in the length, width and water depth directions is defined as the center of the sound source. S2. Place a standard sound source in the reverberation pool and make the equivalent sound center of the standard sound source located at the center of the sound source; on one side of the center of the sound source, on the central axis of the width of the reverberation pool at the same height as the center of the sound source, arrange multiple hydrophones at intervals to form a hydrophone array; the distance between any two adjacent hydrophones is less than one-eighth of the wavelength of the first resonant frequency. S3. Using a single-frequency continuous sinusoidal signal lower than the first-order resonant frequency as the input to the standard sound source, the standard sound source is excited to emit sound. The radiated sound pressure amplitude of the standard sound source is collected using all hydrophones, and the standard sound source radiated sound pressure field fitting model shown in equation (3) is established; where, This is the serial number of the hydrophone. , The number of hydrophones; For the first The distance between the hydrophone and the center of the sound source For the first The standard sound source radiated sound pressure amplitude was collected by a hydrophone; the exponential function adjustment factor was calculated using the least squares method. and standard sound source intensity factor ; (3)； S4. Replace the standard sound source with the sound source to be tested, and excite the sound source to be tested with the same single-frequency continuous sinusoidal signal as in step S3. Use all hydrophones to collect the radiated sound pressure amplitude of the sound source to be tested, and establish the radiated sound pressure field fitting model of the sound source to be tested as shown in equation (18); where... For the first The sound pressure amplitude of the sound source under test was collected by a hydrophone; the intensity factor of the sound source under test was calculated using the least squares method. ; (18)； S5. Calculate the radiated sound power of the sound source under test according to equation (27). ;in, The radiated acoustic power of the standard sound source; (27)。 2. The method for measuring the very low frequency radiated sound power of an omnidirectional sound source in a reverberant water tank according to claim 1, characterized in that, In step S1, the first-order resonant frequency The calculation is performed according to equation (1), where, The speed of sound in water, The length of the reverberation pool For the width of the reverberation pool, The water level in the reverberation tank; (1)。 3. The method for measuring the very low frequency radiated sound power of an omnidirectional sound source in a reverberant water tank according to claim 1, characterized in that, In step S1, the maximum measurable volume of the underwater sound source The calculation is performed according to equation (2); where, The length of the reverberation pool For the width of the reverberation pool, The water level in the reverberation tank; (2)。 4. The method for measuring the very low frequency radiated sound power of an omnidirectional sound source in a reverberant water tank according to claim 1, characterized in that, The net distance between the hydrophone closest to the center of the sound source and the standard sound source or the sound source to be tested is greater than a preset threshold. The preset threshold is determined based on the maximum horizontal dimension of the standard sound source and the sound source to be tested.

5. The method for measuring the very low frequency radiated sound power of an omnidirectional sound source in a reverberant water tank according to claim 1, characterized in that, When the standard sound source or the sound source under test is excited to produce sound with a single-frequency continuous sinusoidal signal, the amplitude of the signal input is adjusted so that the measured signal-to-noise ratio is not less than 6dB.

6. The method for measuring the very low frequency radiated sound power of an omnidirectional sound source in a reverberant water tank according to claim 1, characterized in that, In step S3, the exponential function adjustment factor The standard sound source intensity factor is calculated according to equation (14). The solution is performed according to equation (15); where, The mean distance between the hydrophone and the center of the sound source is calculated according to equation (16); The logarithmic mean of the radiated sound pressure amplitude of the standard sound source is calculated according to equation (17); (14)； (15)； (16)； (17)。 7. The method for measuring the very low frequency radiated sound power of an omnidirectional sound source in a reverberant water tank according to claim 6, characterized in that, In step S4, the intensity factor of the sound source to be measured The solution is performed according to equation (25); where, The logarithmic mean of the amplitude of the radiated sound pressure from the sound source under test is calculated according to equation (26); (25)； (26)。 8. The method for measuring the very low frequency radiated sound power of an omnidirectional sound source in a reverberant water tank according to claim 1, characterized in that, Step S5 further includes calculating the radiated sound power level of the sound source under test according to equation (28). ;in, This is a reference value for the radiated sound power level; (28)。 9. A system for measuring the very low frequency radiated sound power of an omnidirectional sound source in a reverberant water tank, characterized in that, A method for measuring the very low frequency radiated sound power of an omnidirectional sound source in a reverberant water tank as described in any one of claims 1 to 8, wherein the system for measuring the very low frequency radiated sound power of an omnidirectional sound source in a reverberant water tank comprises: The acquisition module is used to excite the standard sound source and the sound source under test to emit sound, and to acquire the radiated sound pressure amplitude data of the standard sound source and the sound source under test. The fitting module is used to establish a fitting model of the standard sound source radiation sound pressure field based on the standard sound source radiation sound pressure amplitude collected by all hydrophones and the distance between the hydrophone and the sound source center, and then use the least squares method to calculate the exponential function adjustment factor and the standard sound source intensity factor; it is also used to establish a fitting model of the sound source radiation sound pressure field to be tested based on the sound source radiation sound pressure amplitude collected by all hydrophones and the distance between the hydrophone and the sound source center, and then use the least squares method to calculate the sound source intensity factor to be tested; The output module is used to calculate and output the radiated sound power of the sound source under test based on the standard sound source intensity factor, the sound source intensity factor under test, and the standard sound source radiated sound power.

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