Laboratory measurement system and method for target floating water outlet noise

Abstract

The invention discloses a laboratory measurement system and method for target floating water outlet noise. The system is composed of a power traction part, a target internal sensing part, a noise signal receiving part and a data acquisition part. According to the system, target floating water outlet transient noise measurement can be completed in an anechoic water tank in a target traction mode. The required measurement environment is an anechoic pool with a high sound field signal-to-noise ratio, the measurement platform is low in hardware requirement, the test cost is low, the target speed and the water outlet posture are convenient to accurately control, the measurement method is high in operability, and the measurement precision is high. Various information such as external field radiation noise, turbulence pulsating pressure, vibration response, flow field distribution images and target change postures in the floating and water outlet process of a target can be comprehensively obtained through careful arrangement of a multi-physical field sensor, and noise in the stable-speed floating stage and noise in the stable-speed water outlet stage are convenient to extract and process; the signal processing method gives consideration to practicability and accuracy, and provides data support for deep analysis of a water noise mechanism.

Description

Technical Field

[0001] The invention relates to the technical field of underwater acoustic measurement, in particular to a laboratory measurement system and method for target surface water noise. Background Art

[0002] Traditional flow noise measurement methods mainly rely on circulating water tank steady flow measurement technology. The core of this method is to adopt a "passive" measurement mode in which the target is stationary and the fluid is flowing. This mode performs well when measuring noise under stable flow conditions. However, when faced with the need to measure transient flow noise, its limitations are fully revealed. The characteristics of transient flow noise are its dynamics and instantaneousness, which requires that the active movement of the target must be considered during the measurement process, that is, the "active" measurement method in which the fluid is stationary and the target is moving is adopted. This is the most direct and necessary measurement strategy.

[0003] Although there is an urgent need to measure transient flow noise, the existing measurement methods are not only limited in number but also quite difficult. At present, the jet noise measurement method is a common attempt in this field. However, there is no mature method system for measuring the floating water noise.

[0004] The phenomenon of buoyancy has a wide range of backgrounds in practical applications, such as the process of underwater vehicles emerging from the water. Although some studies have focused on the characteristics of the water flow field, there is almost no research on the noise characteristics. Further research has revealed that the water flow field and the noise generated are not only affected by the shape and structure of the target itself, but also by the navigation speed and the water angle. These findings undoubtedly increase the complexity and challenge of buoyancy noise measurement.

[0005] In summary, the traditional circulating water tank steady flow measurement method has obvious shortcomings and limitations when facing transient flow noise, especially the measurement of floating water noise. Therefore, a more accurate and effective measurement system and method is urgently needed to meet this complex and important measurement demand. Summary of the invention

[0006] In order to overcome the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a laboratory measurement system and method for target buoyancy noise, which can realize the transient noise measurement of the target buoyancy in the anechoic pool environment by target traction. This scheme selects an anechoic pool with a high sound field signal-to-noise ratio as the measurement environment, which not only reduces the hardware requirements for the measurement platform, but also controls the test cost. At the same time, it makes it easy to accurately control the target speed and water-out posture, and the measurement method is highly operational. Through the careful arrangement of multi-physical field sensors, various types of information such as external field radiation noise, turbulent pulsating pressure, vibration response, flow field distribution image, target change posture, etc. during the target buoyancy process can be fully obtained. The noise in the two stages of steady speed buoyancy and water-out is easy to extract and process. The signal processing method takes into account both practicality and accuracy, providing data support for in-depth analysis of the water noise mechanism.

[0007] The technical solution of the present invention is as follows:

[0008] In one aspect, the present invention provides a laboratory measurement system for target surface water noise, which is characterized by comprising:

[0009] Power traction module: used to control the target's floating speed and water-out posture in the anechoic pool environment to ensure the repeatability and accuracy of the experimental conditions;

[0010] Target internal sensor module: integrated in the target body, used to monitor and record the key parameters of the target's vibration response and internal stress changes during the process of floating up and out of water in real time;

[0011] Noise signal receiving module: equipped with a hydrophone array to capture and distinguish external field radiation noise and turbulent pulsation pressure to ensure the collection of noise signals;

[0012] Data acquisition and processing module: responsible for integrating data from various sensors, realizing the reconstruction of flow field distribution images, dynamic monitoring of target posture changes, and preprocessing and analysis of noise signals, supporting real-time recording of data and subsequent in-depth processing.

[0013] Furthermore, the power traction part includes a servo motor, a controller, a transmission, a motor turntable, a traction rope, and an anti-collision device;

[0014] The servo motor provides power traction, the motor turntable is connected to the target through the traction rope, and the controller controls the motor turntable to rotate to pull the target up. After leaving the water, the motor turntable stops rotating, and the anti-collision device is used to offset the rising inertia of the target to prevent collision damage;

[0015] The servo motor is a permanent magnet synchronous AC servo motor drive, which has the advantages of large torque, high precision, fast response, small inertia and stable output. It is suitable for short-term start-stop working state, has low background noise, and can be fixed horizontally on the water platform to ensure that the turntable is perpendicular to the water surface. If the target is heavy and the motor torque is insufficient, a reducer can be added to increase the torque and thus increase the traction;

[0016] The driver includes modules such as motor power cable interface, host computer signal cable interface, encoder cable, noise filter, control panel, etc. The driver is connected to the servo motor and controls the motor to run and stop through the control panel or self-programmed program;

[0017] The driver has a variety of pulse instructions to choose from. The set pulse number determines the angular velocity of the turntable. The traction speed can be calculated according to the turntable radius, which is the target real-time floating speed. The conversion relationship between the pulse number and the target floating speed is as follows:

[0018]

[0019] Among them, p n : Pulse number; p f : pulse frequency; r: rotation radius;

[0020] The traction rope should preferably be a thin Kevlar rope with high tensile strength, and the tether point of the traction rope and the target should be as flush as possible with the target surface to reduce the interference effect on the flow field. The outer diameter of the motor turntable is a groove type, and the traction rope is retracted and released by rotating and winding;

[0021] The water surface is kept at a certain height distance from the motor turntable to reserve the target ascending deceleration space. The remaining impact speed of the turntable can be estimated based on the maximum speed.

[0022] The anti-collision device is made of soft foam material and is pasted on the platform below the turntable to reduce the impact force between the target and the motor platform, while leaving a gap so as not to affect the pulling of the traction rope.

[0023] Furthermore, the target internal sensing part includes a target, a pulsating pressure sensor, an accelerometer, a small power source, and a collector;

[0024] The pulsating pressure sensor and the accelerometer are installed inside the target, and the installation method is carried out in accordance with the flow noise and vibration response measurement standard, so as to obtain the flow field distribution on the target outer surface and the shell vibration response during the floating and water exiting process, provide data support for further analysis of flow noise and flow-induced vibration radiation noise, and also provide a reference for external radiation noise data processing;

[0025] The small power supply is installed inside the target to provide a stable power supply for the pulsating pressure sensor and the accelerometer;

[0026] The collector is installed inside the target to realize the self-contained collection of pulsating pressure and vibration acceleration;

[0027] The target shell is watertightly treated;

[0028] The overall center of gravity of the target is controlled on the midline, and the weight should be controlled to be slightly larger than the buoyancy. Too much weight will affect the traction speed, while too little weight will be unfavorable for maintaining the initial state underwater.

[0029] Furthermore, the noise signal receiving part includes a vertical receiving array, a streamlined deflector, and a counterweight;

[0030] The vertical receiving array is composed of a plurality of hydrophone array elements, which are used to receive the radiation noise of the target surfacing out of the water. The vertical receiving array is arranged at a certain distance parallel to the target surfacing path, so as to obtain more comprehensive noise in both the surfacing and water surfacing stages.

[0031] The lowest operating frequency band of the hydrophone array element should be around 10 Hz to ensure sufficient sensitivity to the low-frequency noise spectrum. The volume of the hydrophone array element should be as small as possible to reduce the impact on the sound field, and a counterweight should be hung at the bottom of the vertical receiving array to maintain a vertical state. The number of array elements N is set based on the total floating distance of the target, and is mainly placed in the two areas of the stable speed floating stage and near the water surface;

[0032] The vertical receiving array is placed in the streamlined fairing. The fairing is shaped like a long elliptical cylindrical shell with an elliptical streamlined cross section. The long axis of the elliptical cross section points to the target's floating path. The fairing is made of fiberglass sound-permeable material to avoid flow interference on the hydrophone array element and to avoid affecting the reception of the target's floating water noise. The upper end of the streamlined fairing is fixed to the water platform to prevent shaking due to the water flow.

[0033] The counterweight is suspended at the bottom of the vertical receiving array to keep it in a stable vertical state.

[0034] Furthermore, the data acquisition part includes a charge amplifier, a bandpass filter, a multi-channel collector, a computer and a camera;

[0035] After the vertical receiving array receives the signal, it is processed by the charge amplifier and the bandpass filter, and a multi-channel collector is used to collect data on the noise signal received by the hydrophone array;

[0036] The charge amplifier is used to amplify the received signal;

[0037] The collector is used to display the echo waveform, monitor whether the signal is abnormal, and preliminarily estimate the arrival time and intensity of water noise, analyze the interference situation and avoid it in time;

[0038] The total acquisition time T0 includes the acquisition of background noise until the water flow returns to a basically stable state after the target water is discharged, ensuring sufficient frequency resolution (△f = 1 / T0). To avoid spectrum aliasing, the sampling rate fs can be taken as 3 to 5 times the maximum analysis frequency of the noise;

[0039] The computer is used for acquisition, display and control;

[0040] The cameras record the entire process of the target surfacing and emerging from the water, respectively, underwater and above water, so as to study the flow field and the target motion posture.

[0041] On the other hand, the present invention also provides a method for measuring the target surface water noise laboratory measurement system using the above-mentioned target surface water noise laboratory measurement system, which is characterized in that it includes the following steps:

[0042] Preparation stage: Arrange the system in an anechoic water pool with high signal-to-noise ratio to ensure low background noise interference in the measurement environment;

[0043] Parameter setting and calibration: According to the experimental requirements, adjust the parameters of the power traction module to accurately control the target floating speed and water exit posture, and calibrate all sensors to ensure data accuracy;

[0044] Data acquisition: Start the system and synchronously record the external field radiation noise, turbulent pulsation pressure, vibration response, flow field distribution image and target posture change information during the entire process from the target floating up to the water exit;

[0045] Signal processing and analysis, including conversion of the collected vertical receiving line array, pulsating pressure and vibration acceleration data to obtain the actual noise sound pressure value, pulsating pressure value and vibration acceleration value, and further signal processing and analysis, calculate the sound source level, pulsating pressure spectrum level, vibration acceleration level, draw the noise time-frequency diagram, analyze the noise spectrum characteristics and the change law of the sound source level with speed and angle.

[0046] Further, the method specifically includes the following steps:

[0047] Step 1. Site selection and target internal sensor installation:

[0048] 1.1. The noise measurement of the target surfacing is carried out in an anechoic pool. The depth of the pool should ensure that the target has a period of surfacing at a stable speed;

[0049] 1.2. Pulsation pressure sensors and accelerometers are installed inside the target, and the installation method is carried out in accordance with the flow noise and vibration response measurement standards;

[0050] 1.3. Install and debug the collector and power supply device inside the target to ensure that the sensor power supply and collection functions are normal;

[0051] 1.4. Connect the power supply before placing the target in water, set the sampling rate and other acquisition parameters, and set the delay time for starting the acquisition through the timer;

[0052] 1.5. The entire target device is made watertight.

[0053] Step 2. Target and control equipment deployment:

[0054] 2.1. The top of the target is connected to the traction rope and placed at a specified depth close to the bottom of the pool. The upper end of the traction rope is connected to the motor turntable to ensure that the outer diameter groove fits with the traction rope during the rotation of the turntable so that it can be rolled and retracted;

[0055] 2.2. The turntable is connected to the motor, its transmission and the controller. The controller controls the rotation of the motor's turntable and sets the controller pulse number according to the preset speed.

[0056] 2.3. Debug and confirm the motor control function and target motion status before testing;

[0057] 2.4. Deploy underwater and above-water cameras to record the flow field and target posture during the process of the target emerging from the water.

[0058] Step 3. Collection equipment connection and debugging:

[0059] 3.1. Assemble N hydrophones into a vertical receiving array and place them in a streamlined guide cover. Hang a counterweight at the bottom of the vertical receiving array to keep it vertical. The upper end of the streamlined guide cover is fixed to the water platform to prevent it from shaking due to the water flow.

[0060] 3.2. The hydrophone receiving array cable is connected to the charge amplifier, filtered by the pre-filter and connected to the collector for data collection, the sampling rate is set, and the signal changes are previewed in real time;

[0061] 3.3. The entire acquisition system is powered by a voltage stabilizer and grounded to eliminate static noise.

[0062] Step 4. Synchronous acquisition:

[0063] 4.1. Use the real-time display function of the multi-channel collector to observe whether the signal is normal;

[0064] 4.2. Measure the background noise and ensure that the signal-to-noise ratio meets the test requirements;

[0065] 4.3. Carry out the collection of external field radiation noise, target surface pulsating pressure and vibration acceleration signals under different water outlet speeds and angles;

[0066] 4.4. After all working condition tests are completed, the measured target, vertical receiving array, sensor and instruments and equipment are recovered in turn.

[0067] Step 5. Signal processing and analysis:

[0068] 5.1. Based on the collected vertical receiving line array, pulsating pressure and vibration acceleration data, and according to the sensitivity parameters of each sensor, the collected signals are converted according to the following formula to obtain the actual noise sound pressure value, pulsating pressure value and vibration acceleration value.

[0069] 5.1.1. Noise sound pressure processing formula:

[0070]

[0071] Where, S: hydrophone sensitivity, unit: V / μPa; K: hydrophone preamplification factor; V: voltage obtained after hydrophone amplification, unit: V;

[0072] 5.1.2. Pulsation pressure treatment formula:

[0073]

[0074] Where, S0: pressure sensor sensitivity, unit: Pa / V; V(t): sensor output voltage; V offset : Zero offset voltage;

[0075] 5.1.3. Vibration acceleration processing formula:

[0076]

[0077] Among them, V out : output voltage; S: sensitivity of accelerometer.

[0078] 5.2. According to the processed sound pressure, pulsating pressure and vibration acceleration data, the noise components caused by external ultra-low frequency and jitter interference are filtered out through a 10Hz high-pass filter. The noise, pulsating pressure and vibration response of the two time periods of floating at a stable speed and leaving the water are taken out, and the signal processing is performed according to the following method to obtain the sound source level, pulsating pressure spectrum level, and vibration acceleration level, and the noise time-frequency diagram is drawn to analyze the noise spectrum characteristics of the two time periods and the change law of the sound source level with speed and angle.

[0079] 5.2.1. Sound source level calculation formula:

[0080]

[0081] Among them, p ref : underwater reference sound pressure, 1e-6Pa; R: distance from the hydrophone to the geometric center of the target, unit: m;

[0082] 5.2.2. Pulsation pressure spectrum calculation formula:

[0083]

[0084] Among them, S P (f): Power spectral density, unit: Pa 2 / Hz; S1: reference spectral density, 1Pa 2 / Hz;

[0085] 5.2.3. Vibration acceleration level calculation formula:

[0086]

[0087] Where, a0: reference acceleration, 10 -6 m / s 2 .

[0088] Compared with the prior art, the present invention has the following beneficial effects:

[0089] (1) The measurement environment is an anechoic pool with a high signal-to-noise ratio. The measurement platform has low hardware requirements and low test costs. The target speed and water exit posture are easy to control accurately, and the measurement method is highly operable.

[0090] (2) Through the precise arrangement of multi-physical field sensors such as acoustic field, flow field, and vibration, various types of information such as external field radiation noise, turbulent pulsation pressure, vibration response, flow field distribution image, and target change posture during the target's surfacing process can be fully acquired, filling the gap in water noise measurement and enriching the transient noise measurement method;

[0091] (3) The noise during the two stages of steady-speed ascent and water exit is easy to extract and process. The signal processing method takes into account both practicality and accuracy, providing data support for in-depth analysis of the water exit noise mechanism. BRIEF DESCRIPTION OF THE DRAWINGS

[0092] Figure 1 A schematic diagram of a laboratory measurement system for water noise in an embodiment of the present invention;

[0093] Figure 2 It is a schematic diagram of the motor control system of the present invention;

[0094] Figure 3 It is a schematic diagram of the object of the present invention and the internal sensor arrangement;

[0095] Figure 4 The present invention is aimed at the above-mentioned water sensor signal processing flow chart;

[0096] Figure 5 This is a graph showing the variation of the floating speed with depth according to an embodiment of the present invention;

[0097] Figure 6 A water noise signal is emerged on the target of the embodiment of the present invention;

[0098] Figure 7 This is a time-frequency diagram of water noise emerging from a target according to an embodiment of the present invention.

[0099] Numbers in the figure: 1. Anechoic pool platform; 2. Target; 3. Motor turntable; 4. Motor; 5. Driver; 6. Towing rope; 7. Anti-collision device; 8. Pulsating pressure sensor; 9. Accelerometer; 10. Small power supply; 11. Collector; 12. Vertical receiving linear array; 13. Streamlined deflector; 14. Counterweight; 15. Charge amplifier; 16. Bandpass filter; 17. Multi-channel collector; 18. Computer; 19. Camera. DETAILED DESCRIPTION

[0100] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0101] The target surfacing noise laboratory measurement system of this embodiment is specially designed for accurately measuring the noise characteristics of the target during the surfacing process. It integrates four core parts: power traction, internal sensing, noise signal reception and data acquisition, ensuring the comprehensiveness and accuracy of the measurement.

[0102] See also Figure 1 , Figure 1 This is a schematic diagram of a laboratory measurement system for target surface water noise according to an embodiment of the present invention. As shown in the figure, it includes a power traction part, a target internal sensing part, a noise signal receiving part and a data acquisition part.

[0103] 1. The power traction part is responsible for providing traction so that the target can float to the surface of the water according to the predetermined trajectory and speed. It specifically includes servo motor, driver, motor turntable, traction rope and anti-collision device. The following is a detailed explanation of each part:

[0104] The servo motor is used as the power source, and the motor turntable is connected to the target through a traction rope. The rotation of the motor turntable is precisely controlled by the driver, thereby pulling the target to float. After emerging from the water, the motor turntable stops rotating, and the anti-collision device is used to offset the rising inertia of the target to prevent collision damage. The servo motor uses a permanent magnet synchronous AC servo motor, which has the characteristics of large torque, high precision, and fast response. It is suitable for short-term start and stop working conditions, and has low background noise. It can be fixed horizontally on the water platform to ensure that the motor turntable is perpendicular to the water surface. If the target is heavy and the motor torque is insufficient, a reducer can be added to increase the torque and thus increase the traction;

[0105] The driver is used to control the operation and stop of the servo motor. By sending instructions to the servo motor, the rotation of the motor turntable can be accurately controlled, and the speed and direction of the motor can be adjusted, thereby achieving precise control of the target floating speed.

[0106] The driver includes modules such as motor power cable interface, host computer signal cable interface, encoder cable, noise filter, control panel, etc. The motor control system is as follows: Figure 2 As shown. The motor and driver are connected through an encoder cable to achieve measurement and feedback of speed and position. The motor drive power supply is connected to the driver u, v, and w ports through a cable to provide the power required for the motor to operate. Through self-programmed control, precise control of the motor can be achieved, including start, stop, acceleration, deceleration and other actions. The driver supports a variety of pulse instructions, and the set number of pulses determines the angular velocity of the turntable. The more pulses, the greater the angle of rotation of the turntable and the faster the angular velocity. The traction speed, that is, the real-time floating speed of the target, can be calculated based on the radius of the turntable. The conversion relationship between the number of pulses and the target floating speed is as follows:

[0107]

[0108] Where, v is the pulling speed, p n is the pulse number, p f is the pulse frequency, and r is the rotation radius. In this embodiment, the pulse frequency of the motor is set in the range of 1-10000 Hz, and the pulse frequency is set to 500 Hz.

[0109] The traction rope is used to connect the motor turntable and the target to transmit traction. It is advisable to use a thin Kevlar rope with high tensile strength. At the same time, the tether point of the traction rope and the target should be as flush as possible with the target surface to reduce the interference effect on the flow field. The outer diameter of the motor turntable is grooved, and the traction rope is retracted and released by rotating and winding.

[0110] The water surface is kept at a certain height distance from the motor turntable to reserve the target ascending deceleration space. The remaining impact speed of the turntable can be estimated based on the maximum speed.

[0111] The anti-collision device is used to offset the rising inertia of the target after it emerges from the water to prevent it from colliding with the motor platform and causing damage. Soft foam material is pasted on the platform below the turntable to reduce the impact force between the target and the motor platform, while leaving a gap that does not affect the pulling of the traction rope.

[0112] 2. The target internal sensor part is used to measure and record key data such as the external flow field distribution and shell vibration response of the target during the floating and water exiting process. It includes the target, pulsating pressure sensor, accelerometer, small power supply and collector. The schematic diagram of the target and internal sensor layout is shown in the figure. Figure 3 shown.

[0113] The target, the subject that needs to be measured and monitored, can be any object whose flow noise and flow-induced vibration radiation noise characteristics need to be evaluated during the underwater buoyancy and emergence process.

[0114] The pulsation pressure sensor and accelerometer are installed in accordance with the flow noise and vibration response measurement standards to obtain the target outer surface flow field distribution and shell vibration response during the floating and water exiting processes, providing data support for further analysis of flow noise and flow-induced vibration radiation noise, and also providing a reference for external radiation noise data processing.

[0115] A small power supply, mounted inside the target, provides stable power to the pulsating pressure sensor and the accelerometer.

[0116] The collector is installed inside the target to realize the self-contained collection of pulsating pressure and vibration acceleration, that is, to store the data measured by the sensor in the internal memory for subsequent analysis and processing.

[0117] In order to ensure the normal operation of internal components such as sensors and collectors, the target housing needs to be strictly watertight. This can prevent moisture from invading internal components and causing short circuits, corrosion and other faults.

[0118] The overall center of gravity of the target is controlled on the midline to ensure that it can maintain a stable posture during the process of floating up and out of the water. The weight should be controlled to be slightly larger than the buoyancy to ensure that the target can float smoothly but will not be easily washed away by the water flow; too much weight may affect the towing speed, while too little weight is not conducive to the target maintaining its initial state underwater.

[0119] 3. Noise signal receiving part: used to receive the radiated noise generated when the target emerges from the water, including three parts: vertical receiving array, streamlined deflector and counterweight.

[0120] The vertical receiving array consists of six hydrophone elements, which are placed at a certain distance parallel to the target's ascent path, and can obtain more comprehensive noise in the two stages of ascent and out of water. The minimum operating frequency band of each hydrophone element is 10Hz-120kHz, which means that it has sufficient sensitivity to the low-frequency noise spectrum (-171dB). The volume of the hydrophone element is as small as possible to reduce the impact on the sound field. A counterweight is hung at the bottom of the hydrophone element to maintain a vertical state. The number of elements is set with reference to the total ascent distance of the target, and is focused on the two areas of the steady speed ascent stage and near the water surface, so as to more accurately capture the noise signals of these two key stages.

[0121] The streamlined fairing is used to accommodate the vertical receiving array. It is an elongated elliptical cylindrical shell with an elliptical streamlined cross section, and the major axis of the elliptical cross section points to the target's floating path. The fairing is made of fiberglass sound-transmitting material, which can prevent the flow of water from interfering with the hydrophone array elements, and can also prevent the reception of water noise from buoying the target. The upper end of the streamlined fairing is fixed to the water platform to prevent shaking due to the water flow.

[0122] A counterweight is suspended at the bottom of the vertical receiving array to keep the vertical receiving array in a stable vertical state.

[0123] 4. Data acquisition part, used to capture and process noise signals, including charge amplifier, bandpass filter, multi-channel collector, computer and camera.

[0124] The charge amplifier is used to amplify the weak electrical signals received by the vertical receiving array.

[0125] The bandpass filter, which follows the charge amplifier, is used to filter out the frequency range of interest from the amplified signal while suppressing signals at other frequencies.

[0126] The multi-channel collector is used to collect noise signals received by multiple hydrophone array elements at the same time, and display the echo waveform, monitor whether the signal is abnormal, preliminarily estimate the arrival time and intensity of the water noise, analyze the interference situation and avoid it in time. The total acquisition time T0 includes the whole process from background noise acquisition to the water flow returning to basic stability after the target water is out. By setting a sufficient acquisition time, it is possible to ensure sufficient frequency resolution (△f=1 / T0) to more accurately analyze the spectral characteristics of the noise signal. To avoid spectral aliasing, the sampling rate can be taken as 3 to 5 times the maximum analysis frequency of the noise to ensure that all frequency components of interest can be accurately collected. The sampling rate f in this embodiment s Take it as 1M / s.

[0127] Computer is used for acquisition, display and control.

[0128] The cameras are used to record the entire process of the target surfacing and emerging from the water, both underwater and above water, in order to study the flow field and target motion posture.

[0129] Figure 4 The following is a flow chart of the target surface water noise signal processing of the present invention. As shown in the figure, a laboratory measurement method of target surface water noise includes the following steps:

[0130] Step 1. Site selection and target internal sensor installation

[0131] 1.1. Site selection: Select an anechoic pool as the test site, and ensure that the pool depth is sufficient to support the target to float up at a stable speed. The pool depth in this embodiment is 10m. The anechoic pool helps reduce external noise interference and improve test accuracy.

[0132] 1.2. Target internal sensor:

[0133] -Install pulsation pressure sensors and accelerometers to monitor the pressure and vibration inside the target. The installation method refers to the flow noise and vibration response measurement standards to ensure that the sensors can accurately reflect the dynamic changes inside the target;

[0134] -Install and debug the collector and power supply device to ensure the normal power supply and collection functions of the sensor;

[0135] - Before the target is placed in the water, connect the power and set the acquisition parameters, such as the sampling rate and other acquisition parameters 1M / s, and set the delay start time of the acquisition through the timer, so as to accurately capture the noise signal when the target emerges from the water. In this embodiment, the delay start time of the acquisition is 5 minutes;

[0136] - Make the entire target watertight and conduct a tightness check to prevent water from seeping in and affecting sensor performance and test results.

[0137] Step 2. Target and control equipment deployment

[0138] 2.1. Target placement: Connect the top of the target to the traction rope and place it at a specified depth close to the bottom of the pool. The upper end of the traction rope is connected to the motor turntable to ensure that the outer diameter groove fits the traction rope during the rotation of the turntable so that the traction rope can be rolled and released to control the floating speed and depth of the target. In this embodiment, the target is placed underwater 3.5m from the water surface.

[0139] 2.2. Control equipment connection: Connect the turntable to the motor and its driver, control the motor's turntable rotation through the driver, set the controller pulse number according to the preset speed, and set the pulse number to 800Hz and 1300Hz. Before testing, debug and confirm the motor control function and target motion state to ensure a smooth test process.

[0140] 2.3. Camera placement: Place cameras underwater and above water to record the flow field and target posture during the process of the target emerging from the water, providing video data for subsequent flow field analysis and target motion posture research.

[0141] Step 3. Collection device connection and debugging

[0142] 3.1. Collection equipment assembly: Assemble N hydrophones into a vertical receiving array and insert them into a streamlined flow deflector. A counterweight is hung at the bottom of the vertical receiving array to maintain a vertical state, and the upper end of the streamlined flow deflector is fixed to the water platform to prevent shaking due to the water flow; in this embodiment, N=6.

[0143] 3.2. Signal acquisition: Connect the hydrophone receiving array cable to the charge amplifier, and connect it to the collector for data acquisition after filtering by the pre-filter. Set the sampling rate to 1MHz, the acquisition mode to continuous acquisition, and preview the signal changes in real time to ensure that the acquisition process is stable and reliable.

[0144] 3.3. Power supply and grounding: The entire data acquisition part is powered by a voltage stabilizer and grounded to eliminate static noise.

[0145] Step 4. Synchronous acquisition:

[0146] 4.1. Signal observation: Use the real-time display function of the multi-channel collector to observe whether the signal is normal and ensure that the collected data is valid.

[0147] 4.2. Background noise measurement: Measure the background noise before testing to ensure that the signal-to-noise ratio meets the test requirements and avoid the influence of external noise on the test results.

[0148] 4.3. Test condition collection: Carry out the collection of external field radiation noise, target surface pulsating pressure and vibration acceleration signals under test conditions such as different water outlet speeds and angles. By changing the test conditions, obtain noise data under different working conditions.

[0149] 4.4. Equipment recovery: After all working condition tests are completed, the measured target, vertical receiving array, sensors and instruments and equipment are recovered in turn to ensure the safety of the equipment and prepare for the next step of signal processing and analysis.

[0150] Step 5. Signal processing and analysis: By processing and analyzing the collected vertical receiving line array, pulsating pressure and vibration acceleration data, the actual noise sound pressure value, pulsating pressure value and vibration acceleration value can be obtained, and the noise characteristics of the target during the surfacing process can be further understood.

[0151] 5.1. Data conversion:

[0152] Noise sound pressure processing is used to convert the collected voltage signal into the actual noise sound pressure value p (in Pa). The formula is as follows:

[0153]

[0154] Among them, V is the voltage obtained after hydrophone amplification (in V), S is the sensitivity of the hydrophone (in V / μPa), and K is the pre-amplification factor of the hydrophone.

[0155] Pulsating pressure processing is used to convert the collected voltage signal into the actual pulsating pressure value P(t). The formula is as follows:

[0156]

[0157] Where S0 is the sensitivity of the pressure sensor, unit: Pa / V, V(t) is the output voltage of the sensor; V offset is the zero offset voltage.

[0158] Vibration acceleration processing is used to convert the collected voltage signal into the actual vibration acceleration value a. The formula is as follows:

[0159]

[0160] Among them, V out is the output voltage; S is the sensitivity of the accelerometer.

[0161] 5.2. Signal processing and analysis: Based on the processed sound pressure, pulsating pressure and vibration acceleration data, Figure 4 The signal is processed by the method shown in the figure. Through the 10Hz high-pass filter, the noise components caused by external ultra-low frequency and jitter interference are filtered out, and the water noise signal on the target is as follows Figure 6 Then, the noise, pulsating pressure and vibration response of the two time periods of steady speed floating and water exit are taken out, and the extracted data are processed to calculate the sound source level, pulsating pressure spectrum level and vibration acceleration level. The formula is as follows:

[0162] Sound source level calculation formula:

[0163]

[0164] Among them, p ref is the reference sound pressure in water, 1e-6Pa; R is the distance from the hydrophone to the geometric center of the target, unit: m.

[0165] Pulsating pressure spectrum calculation formula:

[0166]

[0167] Among them, S P (f) is the power spectrum density, unit: Pa 2 / Hz; S1 is the reference spectral density, 1Pa 2 / Hz.

[0168] Vibration acceleration level calculation formula:

[0169]

[0170] Where a0 is the reference acceleration, 10 -6 m / s 2 .

[0171] Finally, the noise time-frequency diagram is drawn based on the processed data, such as Figure 7 As shown, the noise spectrum characteristics of the two time periods and the changes in the sound source level with speed and angle are analyzed to achieve a comprehensive and accurate assessment of the noise characteristics and their changes during the target's surfacing process.

[0172] Experiments show that the measurement system of the present invention can complete the transient noise measurement of the target surfacing and emerging from the water by target traction in the anechoic water tank. The measurement environment is an anechoic water tank with a high signal-to-noise ratio of the sound field. The hardware requirements of the measurement platform are low, the testing cost is low, the target speed and water-emerging posture are easy to control accurately, and the measurement method is highly operable. Through the careful arrangement of multi-physical field sensors, various types of information such as external field radiation noise, turbulent pulsating pressure, vibration response, flow field distribution image, target change posture, etc. during the target surfacing and emerging from the water can be fully obtained. The noise in the two stages of steady speed surfacing and emerging from the water is easy to extract and process. The signal processing method takes into account both practicality and accuracy, providing data support for in-depth analysis of the mechanism of water-emerging noise.

[0173] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A laboratory measurement system for water noise emerging from a target, characterized in that include: Power traction module: used to control the target's floating speed and water-out posture in the anechoic pool environment to ensure the repeatability and accuracy of the experimental conditions; Target internal sensor module: integrated in the target body, used to monitor and record the key parameters of the target's vibration response and internal stress changes during the process of floating up and out of water in real time; Noise signal receiving module: equipped with a hydrophone array to capture and distinguish external field radiation noise and turbulent pulsation pressure to ensure the collection of noise signals; Data acquisition and processing module: responsible for integrating data from various sensors, realizing the reconstruction of flow field distribution images, dynamic monitoring of target posture changes, and preprocessing and analysis of noise signals, supporting real-time recording of data and subsequent in-depth processing.

2. The laboratory measurement system for the surface water noise of a target according to claim 1, characterized in that The power traction part includes a servo motor, a driver, a motor turntable, a traction rope and an anti-collision device, wherein the servo motor controls the rotation of the motor turntable through the driver, and then pulls the target to float to the water surface through the traction rope, and the anti-collision device is used to offset the rising inertia of the target after it emerges from the water.

3. The laboratory measurement system of water noise emerging from a target according to claim 2, characterized in that: The outer shell of the target is watertight to ensure the normal operation of internal components such as sensors and collectors, and the overall center of gravity of the target is controlled on the center line to ensure a stable posture during the process of floating up and out of water.

4. The laboratory measurement system for the surface water noise on a target according to claim 1, characterized in that The internal sensing part of the target includes a target, a pulsating pressure sensor, an accelerometer, a small power supply and a collector, wherein the pulsating pressure sensor and the accelerometer are used to measure the external flow field distribution and the shell vibration response of the target during the floating and water exiting process, the small power supply provides power for the sensor, and the collector is used to collect and store the data measured by the sensor.

5. The laboratory measurement system for the surface water noise on a target according to claim 1, characterized in that: The noise signal receiving part includes a vertical receiving array, a streamlined deflector and a counterweight, wherein the vertical receiving array is composed of a plurality of hydrophone array elements and is used to receive the radiated noise generated when the target emerges from the water; the streamlined deflector is used to accommodate the vertical receiving array and reduce water flow interference; the counterweight is suspended at the bottom of the vertical receiving array and is used to maintain the vertical state of the vertical receiving array.

6. The laboratory measurement system for the surface water noise on a target according to claim 5, characterized in that The vertical receiving array is composed of six hydrophone array elements, which are arranged at a certain distance parallel to the target floating path, and the minimum operating frequency band of each hydrophone array element is 10Hz-120kHz, which has sufficient sensitivity.

7. The laboratory measurement system for the surface water noise on a target according to claim 1, characterized in that The data acquisition part includes a charge amplifier, a bandpass filter, a multi-channel collector, a computer and a camera, wherein the charge amplifier is used to amplify the weak electrical signal received by the vertical receiving array, the bandpass filter is used to filter out the signal within the frequency range of interest, the multi-channel collector is used to simultaneously collect noise signals of multiple hydrophone array elements, the computer is used for acquisition display and control, and the camera is used to record the entire process of the target surfacing and after surfacing.

8. The laboratory measurement system for the surface water noise on a target according to claim 7, characterized in that: The data acquisition part also includes a voltage stabilizer for power supply and is grounded to eliminate electrostatic noise. The multi-channel collector sets the sampling rate to 3 to 5 times the maximum noise analysis frequency to ensure that all frequency components of interest can be accurately collected.

9. A method for measuring target surface water noise using the laboratory measurement system of any one of claims 1 to 8, characterized in that: include: Preparation stage: Arrange the system in an anechoic water pool with high signal-to-noise ratio to ensure low background noise interference in the measurement environment; Parameter setting and calibration: According to the experimental requirements, adjust the parameters of the power traction module to accurately control the target floating speed and water exit posture, and calibrate all sensors to ensure data accuracy; Data acquisition: Start the system and synchronously record the external field radiation noise, turbulent pulsation pressure, vibration response, flow field distribution image and target posture change information during the entire process from the target floating up to the water exit; Signal processing and analysis, including conversion of the collected vertical receiving line array, pulsating pressure and vibration acceleration data to obtain the actual noise sound pressure value, pulsating pressure value and vibration acceleration value, and further signal processing and analysis, calculate the sound source level, pulsating pressure spectrum level, vibration acceleration level, draw the noise time-frequency diagram, analyze the noise spectrum characteristics and the change law of the sound source level with speed and angle.

10. The measuring method according to claim 9, characterized in that: The signal processing and analysis also includes filtering out external ultra-low frequency and noise components caused by jitter interference through a 10 Hz high-pass filter, and extracting the noise, pulsating pressure and vibration response in the two time periods of steady speed floating and water exit for signal processing.

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