Anechoic chamber experimental device and method for testing aerodynamic noise of ship ventilation louver

Abstract

Disclosed is a soundproof room experimental device and method for testing the aerodynamic noise of ship ventilation louvers, wherein the experimental device is characterized in that: an external air supply system is arranged in the reverberation chamber; a super-structure sound-absorbing material is laid on the inner wall of the full soundproof room main body; a louver test table is arranged inside the full soundproof room main body and located downstream of the air outlet of the external air supply system; an impeller type air speed measuring instrument is arranged between the air outlet of the external air supply system and the louver test table and the louver air outlet, for real-time monitoring of the airflow speed flowing into and out of the louver; an acoustic testing system is arranged inside the full soundproof room main body; a microphone and a microphone array are respectively installed at different measuring points before and after the louver test table to synchronously collect acoustic signals at multiple measuring points; a data acquisition system is connected with the microphone to synchronously collect acoustic signals at multiple measuring points; and a data processing system is in communication connection with the data acquisition system, for collection and analysis of noise signals.

Description

Technical Field

[0001] This invention relates to the field of aerodynamic noise testing technology for ship ventilation equipment, and in particular to an anechoic chamber experimental device for testing the aerodynamic noise of ship ventilation louvers. Background Technology

[0002] Aerodynamic noise from ship ventilation systems is a significant source of cabin noise, with airflow separation and vortex shedding from ventilation louvers being core factors contributing to this noise. To optimize louver design and reduce noise, precise aerodynamic noise experiments must be conducted in a fully anechoic chamber, while simultaneously controlling noise interference from the air supply system.

[0003] In existing anechoic chamber experiments, the axial flow fan is often placed directly inside the anechoic chamber or near its entrance. Even with low-noise axial flow fans, their operating noise can still interfere with louver noise measurements through direct airflow or structural transmission. Vibration and turbulence noise from the ductwork also contribute to the test signal, reducing accuracy. Traditional experiments often use single-point microphones for signal acquisition, making it difficult to capture the directional characteristics of noise radiation. Furthermore, the linkage between wind speed monitoring and axial flow fan speed control is poor, resulting in insufficient operational stability. Simultaneously, the lack of targeted sound-absorbing and sound-insulating structural design fails to effectively isolate axial flow fan and duct noise, hindering accurate extraction of the true characteristics of louver aerodynamic noise and impacting subsequent noise source tracing and reduction optimization. Therefore, there is an urgent need to design a testing method and device adapted to a fully anechoic chamber, utilizing a reverberation chamber to isolate the external air supply system, and combining a microphone array and impeller-type anemometer. Through multiple sound-absorbing and sound-insulating treatments and precise control, this method can achieve high-precision testing of aerodynamic noise from ship ventilation louvers.

[0004] The information disclosed in the background section is only intended to enhance the understanding of the background of the present invention, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] To address the shortcomings or defects of the existing technology, an anechoic chamber experimental device for testing the aerodynamic noise of ship ventilation louvers is provided. This solves the problems of high noise interference from axial flow fans, limited acoustic signal acquisition, and insufficient testing accuracy in existing experiments.

[0006] The objective of this invention is achieved through the following technical solutions.

[0007] An anechoic chamber experimental apparatus for testing the aerodynamic noise of ship ventilation louvers includes,

[0008] A reverberation chamber provides a sound field.

[0009] The main body of the anechoic chamber is lined with ultra-structural sound-absorbing material on its inner walls, and the side walls have connection ports to connect with the reverberation chamber to provide an acoustic testing environment free from external noise interference.

[0010] An external air supply system, located in a reverberation chamber, includes a stepless speed-regulating low-noise axial flow fan for providing continuous adjustable airflow and an aluminum foil air guide duct, wherein the aluminum foil air guide duct connects the low-noise axial flow fan to a louvered test stand.

[0011] The sound-absorbing and sound-insulating component includes a sound-insulating sleeve fitted onto an aluminum foil air duct, and a super-structured sound-absorbing material and sound-insulating cotton filling the connection between the main body of the reverberation chamber and the anechoic chamber. The outer wall of the sound-insulating sleeve is wrapped with pipe sound-insulating cotton and damping cloth, and the inner wall is bonded with sound-absorbing cotton between the aluminum foil air duct to form a double sound-insulating and sound-absorbing structure.

[0012] The louver test stand is located inside the main body of the anechoic chamber and downstream of the air outlet of the external air supply system. The height of the louver test stand is adjustable and it can fix the ventilation louvers of the ship to be tested.

[0013] An impeller-type anemometer is installed between the air outlet of the external air supply system and the louver test platform, as well as at the louver outlet, to monitor the airflow velocity entering and exiting the louvers in real time.

[0014] An acoustic testing system is installed inside the main body of the anechoic chamber. The acoustic testing system includes a microphone, a microphone array, a data acquisition system, and a data processing system. The microphone and microphone array are installed at different measurement points in front of and behind the louvered test stand to simultaneously acquire acoustic signals from multiple measurement points. The data acquisition system is connected to the microphone to simultaneously acquire acoustic signals from multiple measurement points. The data processing system is communicatively connected to the data acquisition system and is used for noise signal acquisition and analysis.

[0015] In the aforementioned anechoic chamber experimental device for testing aerodynamic noise of ship ventilation louvers, the inner side of the sound insulation sleeve is a vibration damping sheet pasted on the outer wall of the aluminum foil air duct with a thickness of 5mm; the outer sound insulation cotton is 20mm thick high-density cotton with added cotton and rubber; the aluminum foil air duct, damping sheet, and outer sound insulation cotton are bonded together by adhesive backing, and the outermost sound insulation cotton is fixed with cable ties.

[0016] In the anechoic chamber experimental device for testing the aerodynamic noise of ship ventilation louvers, the superstructure sound-absorbing material is filled close to the sound insulation sleeve, the remaining gap in the connection port is filled with sound insulation cotton, and at the same time, 50mm thick sound insulation cotton is pasted on both sides of the connection port to form a gradient noise reduction structure.

[0017] In the anechoic chamber experimental device for testing the aerodynamic noise of ship ventilation louvers, the microphone array adopts a 1×7 channel structure, the distance between adjacent microphones is 0.1m, the array is arranged at a fixed distance on both sides of the louver, and the distance between a single microphone measuring point and the louver outlet is ≥0.15m.

[0018] In the anechoic chamber experimental device for testing the aerodynamic noise of ship ventilation louvers, the low-noise axial flow fan outlet is manually rotated 120° up and down, with a 35° angle fan blade, and the outer shell is made of 2mm thick steel plate. The diameter of the fan blade is determined according to the connected aluminum foil air guide duct.

[0019] In the aforementioned anechoic chamber experimental device for testing the aerodynamic noise of ship ventilation louvers, the aluminum foil air guide duct is made of flame-retardant aluminum foil with a thickness of ≥0.2mm. The duct diameter is compatible with the air outlet of the low-noise axial flow fan and the test louvers, and the length meets the installation requirements of connecting one end to the axial flow fan in the reverberation chamber and extending the other end to the louver test platform in the fully anechoic chamber.

[0020] A test method for an anechoic chamber experimental apparatus for testing the aerodynamic noise of ship ventilation louvers includes,

[0021] S1, Experimental setup and debugging: Adjust the height of the base of the low-noise axial flow fan to be flush with the height of the connection port. One end of the aluminum foil air guide pipe is sealed to the air outlet of the low-noise axial flow fan through a flexible soundproof joint, and the other end passes through the connection port and extends into the main body of the anechoic chamber. Place the louver to be tested on the louver test platform. Adjust the height of the louver test platform so that the louver to be tested is directly opposite the air outlet of the aluminum foil air guide pipe. Install a microphone and microphone array, and connect the data acquisition system and data processing system. Install two impeller-type anemometers between the air outlet of the external air supply system and the louver test platform, and at the air outlet of the louver, respectively.

[0022] S2, Real-time wind speed calibration: The impeller-type anemometer records the airflow speed every 10-15 seconds and adjusts the speed of the low-noise axial flow fan to ensure that the wind speed fluctuation is ≤0.2m / s;

[0023] S3, Background noise measurement: Move the louver to be tested out of the louver test stand, start the low-noise axial flow fan and adjust it to the target wind speed, use an impeller-type anemometer to monitor the airflow speed, and simultaneously collect the background noise signal in the main body of the anechoic chamber through a microphone and microphone array.

[0024] S4, Louver aerodynamic noise measurement: Fix the louver to be tested on the louver test stand, keep the low-noise axial flow fan running, monitor the wind speed in real time through the impeller-type anemometer to ensure that the airflow speed is stable at the target value, and collect the total noise signal including louver aerodynamic noise through the microphone and microphone array simultaneously.

[0025] S5, Noise signal processing: Subtract the sound pressure level of the background noise signal from the sound pressure level of the total noise signal to obtain the preliminary louver aerodynamic noise signal; Combined with the low-noise fan operating parameters, calculate the interference frequency using the fan rotation discrete noise characteristic frequency formula, locate the corresponding frequency and surrounding interference peaks, and remove them to obtain the louver aerodynamic noise signal.

[0026] S6, Multi-condition test: Adjust the speed of the low-noise axial flow fan to change the wind speed, repeat steps S1-S5, and complete the louver aerodynamic noise test under several conditions of 3.5m / s, 4.0m / s, 4.5m / s, and 5.0m / s.

[0027] In the method described, the background noise signal includes low-noise axial fan operating noise, duct turbulence noise, and ambient background noise. The sound pressure level of the background noise signal is at least 10 dB lower than the sound pressure level of the total noise signal, and the signal-to-noise ratio of the signal acquired by the microphone array is ≥20 dB.

[0028] In the method described above, the interference frequency is calculated using the discrete noise characteristic frequency formula of the fan rotation. The discrete noise characteristic frequency formula of the fan rotation is shown below. Based on the calculation results, the corresponding frequency and surrounding interference peaks are located in the spectrum and removed.

[0029]

[0030] In the formula, —Discrete frequency characteristic of fan rotation noise; —Harmonic orders, taken from 1st to 3rd, corresponding to the fan's fundamental frequency and main harmonic interference; —Number of blades in a low-noise axial fan; —Actual fan speed, in r / min.

[0031] In the method described, the sampling time of the microphone and microphone array is ≥30s, the sampling frequency is 12.8kHz, and the measurement accuracy of the impeller-type anemometer is ±2%.

[0032] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention places the external air supply system within a reverberation chamber, combined with a sound insulation and protection structure and a dual sound insulation and noise reduction structure consisting of "sound-absorbing cotton + duct sound insulation cotton + damping cloth," achieving multiple isolations of axial fan noise, duct vibration, and turbulent noise, significantly improving the signal-to-noise ratio of the test; it employs a steplessly speed-adjustable low-noise axial fan paired with an impeller-type anemometer, ensuring wind speed fluctuations within ±0.2 m / s of the rated operating wind speed, with a measurement accuracy of ±2%, while also incorporating a combination of microphone and microphone array for data acquisition. This method, combined with background noise subtraction and residual fan noise removal steps, accurately extracts the sound pressure level and spectral characteristics of louver aerodynamic noise, providing a more comprehensive testing dimension. The experimental setup is highly versatile, allowing for adjustment of the test height via the louver test stand and change of the wind speed via a continuously variable axial fan, adapting to the testing needs of ship ventilation louvers under different structural parameters and operating conditions. The testing method is standardized, with high data repeatability, providing reliable experimental support for the study of noise characteristics, source analysis, and low-noise structure optimization of ship ventilation louvers, demonstrating significant engineering application value.

[0033] The description provided is merely an overview of the technical solution of this invention. In order to make the technical means of this invention clearer and more understandable, so that those skilled in the art can implement it according to the contents of the specification, and to make the described and other objects, features and advantages of this invention more obvious and understandable, specific embodiments of this invention are described below. Attached Figure Description

[0034] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0035] In the attached diagram:

[0036] Figure 1 This is a schematic diagram of an experimental device for testing aerodynamic noise of ship ventilation louvers according to an embodiment of the present invention;

[0037] Figure 2 This is a schematic diagram of the aerodynamic noise test procedure for ship ventilation louvers according to an embodiment of the present invention;

[0038] Figure 3 This is a time-domain and frequency-domain signal diagram corresponding to background noise according to an embodiment of the present invention;

[0039] Figure 4 This is a time-domain and frequency-domain signal diagram corresponding to the total test noise according to an embodiment of the present invention;

[0040] Figure 5 This is a frequency response curve of the louver aerodynamic noise signal obtained after differential and noise reduction processing according to an embodiment of the present invention.

[0041] Figure 6 This is a schematic diagram of the main frequency of the louver aerodynamic noise signal and the peak sound pressure level after five-point averaging, obtained after differential and noise reduction processing according to an embodiment of the present invention.

[0042] The present invention will be further explained below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0043] Specific embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While specific embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0044] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions are preferred embodiments for carrying out the invention; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of the invention. The scope of protection of this invention is determined by the appended claims.

[0045] To facilitate understanding of the embodiments of the present invention, the following will provide further explanation and description with reference to the accompanying drawings and several specific embodiments, and the accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0046] To better understand, such as Figures 1 to 6 As shown, an anechoic chamber experimental apparatus for testing the aerodynamic noise of ship ventilation louvers includes,

[0047] Reverberation chamber 1 provides the sound field.

[0048] The main body 2 of the anechoic chamber has an inner wall lined with super-structure sound-absorbing material 3, and a connection port 9 on the side wall to connect with the reverberation chamber 1 to provide an acoustic testing environment free from external noise interference.

[0049] An external air supply system is installed in the reverberation chamber 1. The external air supply system includes a stepless speed-regulating low-noise axial flow fan 12 for providing continuously adjustable experimental airflow and an aluminum foil air guide duct 8. The aluminum foil air guide duct 8 connects the low-noise axial flow fan 12 and the louvered test stand 5.

[0050] The sound-absorbing and sound-insulating component includes a sound-insulating sleeve 7 fitted onto an aluminum foil air duct 8, a super-structure sound-absorbing material 3 and sound-insulating cotton filling the connection 9 between the reverberation chamber 1 and the main body 2 of the anechoic chamber. The outer wall of the sound-insulating sleeve 7 is wrapped with pipe sound-insulating cotton and damping cloth, and the inner wall is bonded with sound-absorbing cotton between the aluminum foil air duct 8 to form a double sound-insulating and sound-absorbing structure.

[0051] The louver test stand 5 is located inside the main body 2 of the anechoic chamber and downstream of the air outlet of the external air supply system. The height of the louver test stand 5 is adjustable and it fixes the ventilation louvers of the ship to be tested.

[0052] An impeller-type anemometer is installed between the air outlet of the external air supply system and the louver test stand 5, as well as at the louver outlet, to monitor the airflow velocity entering and exiting the louvers in real time.

[0053] An acoustic testing system is installed inside the anechoic chamber 2. The acoustic testing system includes a microphone, a microphone array, a data acquisition system, and a data processing system. The microphone and microphone array are installed at different measurement points in front of and behind the louvered test stand 5 to simultaneously acquire acoustic signals from multiple measurement points. The data acquisition system is connected to the microphone to simultaneously acquire acoustic signals from multiple measurement points. The data processing system is communicatively connected to the data acquisition system and is used for noise signal acquisition, analysis, and feedback.

[0054] In a preferred embodiment of the anechoic chamber experimental device for testing the aerodynamic noise of ship ventilation louvers, the inner side of the sound insulation sleeve 7 is a vibration damping sheet pasted on the outer wall of the aluminum foil air duct 8, with a thickness of 5mm; the outer sound insulation cotton is 20mm thick high-density cotton with added cotton and rubber; the aluminum foil air duct 8, the damping sheet, and the outer sound insulation cotton are bonded together by adhesive backing, and the outermost sound insulation cotton is fixed with cable ties.

[0055] In a preferred embodiment of the anechoic chamber experimental device for testing the aerodynamic noise of ship ventilation louvers, the superstructure sound-absorbing material 3 is filled close to the sound insulation sleeve 7, the remaining gap in the connection port 9 is filled with sound insulation cotton, and at the same time, 50mm thick sound insulation cotton is pasted on both sides of the connection port 9 to form a gradient noise reduction structure 10.

[0056] In a preferred embodiment of the anechoic chamber experimental device for testing aerodynamic noise of ship ventilation louvers, the microphone array adopts a 1×7 channel structure, the spacing between adjacent microphones is 0.1m, the array is arranged at a fixed distance on both sides of the louver, and the distance between a single microphone measuring point and the louver outlet is ≥0.15m.

[0057] In a preferred embodiment of the anechoic chamber experimental device for testing the aerodynamic noise of ship ventilation louvers, the low-noise axial flow fan 12 is manually rotated 120° up and down at the air outlet, uses a 35° angle fan blade, has a 2mm thick steel plate outer shell, and the fan blade diameter is determined according to the connected aluminum foil air guide duct 8.

[0058] In a preferred embodiment of the anechoic chamber experimental device for testing the aerodynamic noise of ship ventilation louvers, the aluminum foil duct 8 is made of flame-retardant aluminum foil with a thickness ≥0.2mm. The duct diameter is compatible with the air outlet of the low-noise axial flow fan 12 and the test louvers, and the length meets the installation requirements of connecting one end to the axial flow fan in the reverberation chamber 1 and extending the other end to the louver test platform 5 in the fully anechoic chamber.

[0059] A test method for an anechoic chamber experimental apparatus for testing the aerodynamic noise of ship ventilation louvers includes,

[0060] S1, Experimental setup and debugging: Adjust the height of the base of the low-noise axial flow fan 12 to be flush with the height of the connection port 9. One end of the aluminum foil air guide duct 8 is sealed to the air outlet of the low-noise axial flow fan 12 through a flexible soundproof joint, and the other end passes through the connection port 9 and extends into the main body 2 of the anechoic chamber. Place the louver to be tested on the louver test platform 5. Adjust the height of the louver test platform 5 so that the louver to be tested is directly opposite the air outlet of the aluminum foil air guide duct 8. Install a microphone and microphone array, and connect the data acquisition system and the data processing system. Install two impeller-type anemometers between the air outlet of the external air supply system and the louver test platform 5, and at the louver air outlet, respectively.

[0061] S2, Real-time wind speed calibration: The impeller-type anemometer records the airflow speed every 10-15 seconds and adjusts the speed of the low-noise axial flow fan to 12 to ensure that the wind speed fluctuation is ≤0.2m / s;

[0062] S3, Background noise measurement: Move the louver to be tested out of the louver test stand 5, start the low-noise axial flow fan 12 and adjust it to the target wind speed, use the impeller-type anemometer to monitor the airflow speed, and synchronously collect the background noise signal in the main body 2 of the anechoic chamber through the microphone and microphone array.

[0063] S4, Louver aerodynamic noise measurement: Fix the louver to be tested on the louver test stand 5, keep the low-noise axial flow fan 12 running, monitor the wind speed in real time through the impeller-type anemometer to ensure that the airflow speed is stable at the target value, and collect the total noise signal including louver aerodynamic noise through the microphone and microphone array simultaneously.

[0064] S5, Noise signal processing: Subtract the sound pressure level of the background noise signal from the sound pressure level of the total noise signal to obtain the preliminary louver aerodynamic noise signal; Combined with the low-noise fan operating parameters, calculate the interference frequency using the fan rotation discrete noise characteristic frequency formula, locate the corresponding frequency and surrounding interference peaks, and remove them to obtain the louver aerodynamic noise signal.

[0065] S6, Multi-condition test: Adjust the speed of the low-noise axial fan to 12 to change the wind speed, repeat steps S1-S5, and complete the louver aerodynamic noise test under different operating conditions.

[0066] In a preferred embodiment of the method, the background noise signal includes the operating noise of the low-noise axial flow fan 12, the turbulence noise of the duct, and the ambient background noise. The sound pressure level of the background noise signal is more than 10 dB lower than the sound pressure level of the total noise signal, and the signal-to-noise ratio of the signal collected by the microphone array is ≥20 dB.

[0067] In a preferred embodiment of the method, the interference frequency is calculated using the discrete noise characteristic frequency formula of the fan rotation, which is shown below. Based on the calculation results, the corresponding frequency and surrounding interference peaks are located in the spectrum and removed.

[0068]

[0069] In the formula, —Discrete frequency characteristic of fan rotation noise; —Harmonic orders, taken from 1st to 3rd, corresponding to the fan's fundamental frequency and main harmonic interference; —Number of blades in a low-noise axial fan; —Actual fan speed, in r / min.

[0070] In a preferred embodiment of the method, the sampling time of the microphone and microphone array is ≥30s, and the sampling frequency is 12.8kHz; the measurement accuracy of the impeller-type anemometer is ±2%.

[0071] In one embodiment, an anechoic chamber experimental apparatus for testing the aerodynamic noise of ship ventilation louvers includes:

[0072] The main body 2 of the anechoic chamber has lightweight superstructure sound-absorbing material 3 on its inner wall to provide a non-reflective acoustic testing environment. The side wall has a connection port 9 to connect to the reverberation chamber 1 to provide an acoustic testing environment without external noise interference.

[0073] An external air supply system is installed in the reverberation chamber 1, which is independent of the main body 2 of the anechoic chamber. It includes a low-noise axial flow fan 12 with stepless speed regulation and an aluminum foil air guide duct 8. The low-noise axial flow fan 12 is used to provide a continuously adjustable experimental airflow. The aluminum foil air guide duct 8 connects the low-noise axial flow fan 12 to more than 100 test benches. The smooth inner wall reduces the airflow resistance and enhances the sealing performance. The reverberation chamber 1, together with the sound insulation and protection structure, achieves double isolation of the axial flow fan noise.

[0074] The sound-absorbing and sound-insulating assembly includes a sound-insulating sleeve 7 fitted onto the aluminum foil duct 8, and a super-mechanical sound-absorbing material and sound-insulating cotton filling the reverberation chamber 1-anechoic chamber connection port 9. The outer wall of the sound-insulating sleeve 7 is wrapped with pipe sound-insulating cotton and damping cloth, and the inner wall is fitted with sound-absorbing cotton between itself and the aluminum foil duct 8, forming a double sound-insulating and sound-absorbing structure, which can effectively attenuate the airflow turbulence noise inside the aluminum foil duct 8 and the noise radiated outside the pipe; the super-mechanical sound-absorbing material and sound-insulating cotton in the connection port 9 are superimposed and filled to completely block noise interference from the reverberation chamber 1.

[0075] The louver test stand 5 is located inside the main body 2 of the anechoic chamber, downstream of the air outlet of the external air supply system. Its height is adjustable and it is used to fix the ventilation louvers of the ship under test. A vibration damping pad is set between the test stand and the ground of the main body 2 of the anechoic chamber.

[0076] An impeller-type anemometer is installed between the air outlet of the air supply system and the louver test stand 5, and at the louver outlet to monitor the airflow velocity flowing into and out of the louvers in real time.

[0077] An acoustic testing system, located inside the anechoic chamber 2, includes a microphone, a microphone array, a data acquisition system, and a data processing system. The microphone and microphone array are installed at different measurement points before and after the louvered test stand 5. The data acquisition system is connected to the microphones for synchronously acquiring acoustic signals from multiple measurement points. The data processing system is communicatively connected to the data acquisition system for noise signal acquisition, analysis, and feedback. The low-noise axial flow fan 12 has a 120° manual vertical rotation outlet, uses a 35° large-angle blade, and has a 2mm thick steel outer shell. The blade diameter is determined by the connected aluminum foil duct 8, and it allows for stepless speed adjustment to achieve multi-condition measurements. The aluminum foil duct 8 is an external air supply system, made of flame-retardant aluminum foil with a thickness ≥0.2mm. Its diameter matches the outlet of the low-noise axial flow fan 12 and the test louvers, and its length meets the installation requirement of "one end connecting to the axial flow fan inside the reverberation chamber 1, and the other end extending to the louvered test stand 5 inside the anechoic chamber." The sound insulation sleeve 7... The side is a 5mm thick, honeycomb aluminum sheet attached to the outer wall of the aluminum foil air duct 8; the outer sound insulation cotton is 20mm thick and is high-density cotton-reinforced rubber and plastic cotton; the aluminum foil air duct 8, the damping sheet, and the outer sound insulation cotton are bonded together by adhesive backing, and the outermost sound insulation cotton is fixed with cable ties at certain intervals; in the connection port 9 between the reverberation chamber 1 and the anechoic chamber, the sound-absorbing material of the super-mechanical structure is filled close to the sound insulation sleeve 7, and the remaining gap in the connection port 9 is filled with sound insulation cotton. At the same time, 50mm thick sound insulation cotton is attached to both sides of the connection port 9 to form a gradient noise reduction structure, which completely isolates the noise of the reverberation chamber 1.

[0078] A test method for a ship ventilation louver aerodynamic noise anechoic chamber based on the aforementioned device includes the following steps:

[0079] S1, Experimental Setup and Debugging: Adjust the height of the base of the steplessly speed-adjustable low-noise axial fan 12 so that its height is flush with the connection port 9 between the reverberation chamber 1 and the anechoic chamber. One end of the aluminum foil duct 8 is sealed to the outlet of the low-noise axial fan 12 via a flexible soundproof joint, and the other end passes through the connection port 9 (i.e., the duct installation hole) between the reverberation chamber 1 and the anechoic chamber, extending into the anechoic chamber. Assemble the soundproofing components: first, place the soundproof sleeve 7 on the section of the aluminum foil duct 8 that passes through the connection port 9; then, fill the connection port 9 with ultrasonic sound-absorbing material and sound-insulating cotton in sequence around the soundproof sleeve 7, ensuring a tight, gapless filling. Check... Ensure that the sound insulation cotton and damping cloth on the outer wall of the sound insulation sleeve 7 are firmly attached, and that the sound-absorbing and sound-insulating materials at the connection port 9 are installed in place; place the ventilation louvers of the ship to be tested on the louver test platform 5, and adjust the height of the test platform so that the louvers are directly opposite the air outlet of the aluminum foil air guide duct 8; install microphones and microphone arrays at the preset measurement points in the anechoic chamber, respectively, and arrange them in front of and behind the louver test platform 5, and then connect the data acquisition system and data processing system in sequence; install two impeller-type anemometers between the air outlet of the external air supply system and the louver test platform 5, and at the air outlet of the louvers, respectively, and complete the calibration to achieve synchronous monitoring of the airflow velocity flowing into and out of the louvers.

[0080] S2, Real-time wind speed calibration: During the experiment, the impeller-type anemometer records the airflow speed every 10 to 15 seconds and adjusts the speed of the low-noise axial flow fan 12 in a timely manner to ensure that the wind speed fluctuation is ≤0.2m / s and to ensure the stability of the experimental conditions.

[0081] S3, Background noise measurement: Move the louver to be tested out of the louver test stand 5, start the low-noise axial flow fan 12 in the reverberation chamber 1 and adjust the speed of the axial flow fan to the target wind speed (e.g., 5m / s), use an impeller-type anemometer to monitor the airflow speed, and after stabilization, synchronously collect the background noise signal in the anechoic chamber through a microphone and microphone array. The background noise includes the operating noise of the low-noise axial flow fan 12, the turbulence noise of the duct, and the ambient background noise.

[0082] S4, Louver aerodynamic noise measurement: Fix the louver to be tested on the louver test stand 5, keep the low-noise axial flow fan 12 running, monitor the wind speed in real time through the impeller-type anemometer to ensure that the airflow speed is stable at the target value, and collect the total noise signal including the louver aerodynamic noise through the microphone and microphone array simultaneously. The collection time is consistent with the background noise measurement.

[0083] S5, Noise Signal Processing:

[0084] S51, Background noise removal: The data processing system preprocesses the signals collected by the microphone and microphone array, and subtracts the sound pressure level of the background noise signal from the sound pressure level of the total noise signal to obtain the preliminary louver aerodynamic noise signal.

[0085] S52, Residual Noise Removal: Combining the low-noise fan operating parameters, the interference frequency is calculated using the formula for the characteristic frequency of discrete fan rotation noise. The formula for the characteristic frequency of discrete fan rotation noise is:

[0086]

[0087] In the formula, —Discrete frequency characteristic of fan rotation noise; —Harmonic orders, taken from 1st to 3rd, corresponding to the fan's fundamental frequency and main harmonic interference; —Number of blades in a low-noise axial fan; —Actual fan speed, in r / min.

[0088] Based on the calculation results, the corresponding frequency and surrounding interference peaks are located and removed from the spectrum diagram to further purify the louver aerodynamic noise signal, ensuring that the signal is free of residual fan interference and meets the test signal-to-noise ratio requirements.

[0089] S6, Multi-condition test: Adjust the speed of the low-noise axial fan to change the wind speed (e.g., 2m / s, 4m / s, 6m / s), repeat the above steps, complete the louver aerodynamic noise test under different operating conditions, and form a complete characteristic database.

[0090] In step S5, the sound pressure level of the background noise must be at least 10 dB lower than the sound pressure level of the total noise signal, and the signal-to-noise ratio of the signal acquired by the microphone array must be at least 20 dB to ensure the accuracy of background noise subtraction and directional characteristic analysis.

[0091] In one embodiment, such as Figure 1 As shown, an anechoic chamber experimental apparatus for testing the aerodynamic noise of ship ventilation louvers includes,

[0092] The main body of the anechoic chamber 2: its inner wall is lined with lightweight superstructure sound-absorbing material 3, with a sound absorption coefficient of more than 95% in the 50Hz-20000Hz frequency band, which can provide a non-reflective acoustic testing environment; the side wall has a connection port 9 to connect with the reverberation chamber 1, the connection port is 0.5m long, which is used to provide an acoustic testing environment without external noise interference.

[0093] External air supply system: A reverberation chamber 1 is independently installed outside the fully anechoic chamber. A low-noise axial flow fan 12 with stepless speed regulation is installed inside the reverberation chamber 1. The fan has an outer diameter of 0.67m, a maximum power of 1100W, and an air volume of 1000~15000 m³ / h. 3 / h, speed 1000~1450 r / min, noise 52-60 dB / A, the axial flow fan is placed on the base 11 with a height of 1.1m, ensuring that the fan is at the same height as the connection port 9 of the reverberation chamber-anechoic chamber; the aluminum foil duct 8 has an inner diameter of 0.7m and a total length of 3.5m, and is fully extended through the connection port, of which the length of the reverberation chamber part is 1m, the length of the connection port part is 0.5m, and the length of the anechoic chamber part is 2m; the inner part of the aluminum foil duct in the reverberation chamber is connected and fixed to the low-noise axial flow fan by metal clamps.

[0094] Soundproofing and noise reduction components: The inner side of the soundproof sleeve 7 is a 5mm thick, honeycomb-shaped damping sheet adhered to the outer wall of the aluminum foil air duct; the outer sound insulation cotton is 20mm thick and is high-density cotton-reinforced rubber and plastic cotton; the aluminum foil air duct, damping sheet, and outer sound insulation cotton are bonded together by adhesive backing, and the outermost sound insulation cotton is fixed with cable ties at certain intervals; in the reverberation chamber-anechoic chamber connection port, the sound-absorbing material of the super-mechanical structure is filled close to the soundproof sleeve, and the remaining gap in the connection port is filled with sound insulation cotton. At the same time, 50mm thick sound insulation cotton is pasted on both sides of the connection port to form a gradient noise reduction structure 10, which completely isolates the noise of the reverberation chamber.

[0095] Louver Test Stand 5: Construct a steel louver test stand. The height and angle of the louver to be tested can be adjusted by adjusting bolts. Install 20mm thick rubber vibration damping pads at the bottom of the test stand. Fix the ventilation louver of the ship to be tested (37 blades, 2mm blade thickness) in the center of the test stand to ensure that the louver is aligned with the airflow direction.

[0096] Acoustic testing system: Fourteen high-precision microphones (model: MNP21, frequency range 20Hz~20KHz, range 18dB~136dB, sensitivity 50mV / Pa) are installed in two horizontally arranged 7-channel microphone arrays (array element spacing 0.1m); microphone array 4 is located 0.15m directly in front of the outlet of the aluminum foil duct of the anechoic chamber, at the same height as the center of the duct outlet; the second microphone array 6 is located in the direction of the louver outlet, 0.15m away from the louver to be tested, at the same height as microphone array 4 and with the sensors aligned front and back; the microphones and microphone arrays are connected to a multi-channel data acquisition system (model: MI-8018M, number of channels 48, amplitude accuracy 0.2%, frequency accuracy 0.001%) via shielded data cables.

[0097] Impeller-type anemometer: A Delixi impeller-type anemometer (model: DLY-1601A, range 0~30m / s, measurement accuracy ±2%) was selected to measure the wind speed in real time at microphone array 4 and the second microphone array 6 respectively, with the probe parallel to the airflow direction.

[0098] like Figure 2 As shown, the experimental steps for testing the aerodynamic noise of ship ventilation louvers include:

[0099] S1 Experimental Setup and Debugging: Check the integrity of the anechoic chamber and soundproofing components, ensuring that the pipe insulation cotton and damping cloth are undamaged and the gaps are properly sealed; start the low-noise axial flow fan in the reverberation chamber, adjust the wind speed to 5m / s, use an impeller-type anemometer to monitor the airflow speed, and fine-tune the axial flow fan speed to stabilize the wind speed fluctuation within ±0.2m / s; check the connection status of the microphone, microphone array and data acquisition system, perform signal calibration, and ensure that the acquired signal is clear and free of interference.

[0100] S2 Real-time wind speed calibration: The impeller-type anemometer repeatedly measures the airflow velocity at the louver inlet five times and adjusts the speed of the low-noise axial fan in time to maintain the airflow velocity at the louver inlet at 5m / s, ensuring that the wind speed fluctuation is ≤±0.2m / s and guaranteeing the stability of the experimental conditions.

[0101] S3 Background Noise Measurement: Without installing the test louvers, start the data acquisition system, set the sampling time to 30s, and the sampling frequency to 12.8kHz. Use the microphone and microphone array between the air duct and the louver test stand to synchronously collect the background noise signal in the anechoic chamber, and record the background noise spectrum and array signal data.

[0102] S4 Louver Aerodynamic Noise Measurement: Fix the louver to be tested on the louver test stand, keep the low-noise axial flow fan running, monitor the air velocity at the louver inlet in real time through an impeller-type anemometer to ensure that the airflow velocity is stable at the target value, and collect the total noise signal including the louver aerodynamic noise through a microphone and microphone array placed on the side of the louver outlet. The collection time is consistent with the background noise measurement.

[0103] S5 noise signal processing:

[0104] S51 Background Noise Reduction: The acquired signal is filtered and preprocessed using noise analysis software to remove environmental interference noise. The total noise sound pressure level is subtracted from the background noise sound pressure level to obtain the preliminary louver aerodynamic noise signal.

[0105] S52 Residual Noise Removal: Based on the low-noise fan operating parameters, the interference frequency is calculated using the formula for the characteristic frequency of discrete fan rotation noise. The formula for the characteristic frequency of discrete fan rotation noise is:

[0106]

[0107] In the formula, —Discrete frequency characteristic of fan rotation noise; —Harmonic orders, taken from 1st to 3rd, corresponding to the fan's fundamental frequency and main harmonic interference; —Number of blades in a low-noise axial fan; —Actual fan speed, in r / min.

[0108] Based on the calculation results, the corresponding frequency and surrounding interference peaks are located and removed from the spectrum diagram to further purify the louver aerodynamic noise signal, ensuring that the signal is free of residual fan interference and meets the test signal-to-noise ratio requirements.

[0109] S6 Multi-condition test: Adjust the speed of the low-noise axial flow fan to stabilize the air velocity at the louver inlet at 5m / s, 4.5m / s, 4m / s, and 3.5m / s respectively. Repeat the above steps to complete the test of 4 sets of conditions. Record the air velocity data, noise spectrum and radiation direction characteristics of each set of conditions to form a database of flow-noise characteristics of ship ventilation louvers, providing data support for subsequent structural optimization.

[0110] In one embodiment, such as Figure 3 As shown, the background noise in the anechoic chamber mainly includes discrete noise from fan rotation, turbulent noise from airflow inside the aluminum foil duct, and external radiation noise. In the spectrum diagram, there are no obvious dominant frequencies or harmonics in the section below 500Hz, and the overall trend is relatively flat.

[0111] In one embodiment, such as Figure 4 As shown, the time-domain and frequency-domain signal graphs corresponding to the total test noise are in Figure 3 Based on the background noise, a significant 100Hz main frequency and harmonics were added, the added part being the aerodynamic noise generated by the ship's ventilation louvers.

[0112] In one embodiment, such as Figure 5 As shown, the total noise signal of the test is subtracted from the background noise signal, and noise reduction processing is performed to obtain the aerodynamic noise signal generated only by the ship's ventilation louvers.

[0113] In one embodiment, such as Figure 6 As shown, the main frequency of the aerodynamic noise signal of the ship ventilation louvers after differential and noise reduction processing is 100Hz, and the peak sound pressure level obtained by the five-point averaging method is 44.27dB.

[0114] Furthermore, this invention constructs a complete noise testing system through four technical means: "reverberation chamber isolation + double sound insulation and silencing structure + background noise reduction + residual noise removal." First, the steplessly adjustable low-noise axial flow fan of the external air supply system is completely placed within the reverberation chamber. One end of the aluminum foil duct is connected to the fan, and the other end leads to the silencing chamber, utilizing the acoustic characteristics of the reverberation chamber and the sound insulation and protection structure to achieve double isolation of the axial flow fan noise. Second, a gradient silencing structure of "sound insulation sleeve + sound-absorbing cotton + pipe sound insulation cotton + damping cloth" forms a double sound insulation and silencing layer from the inner wall to the outer wall of the aluminum foil duct, effectively attenuating the turbulent noise of the airflow inside the aluminum foil duct and the radiated noise outside the duct. Third, a 1×7-channel... A microphone array is positioned before and after the louver test stand. Combined with real-time wind speed monitoring (fluctuation ≤0.2m / s) using an impeller-type anemometer, residual interference is eliminated through background noise subtraction (requiring the background noise sound pressure level to be at least 10dB lower than the total noise signal) and calculation using the discrete noise characteristic frequency formula of the fan rotation (locating and eliminating corresponding frequencies and surrounding interference peaks). This improves the signal-to-noise ratio of the microphone array to over 20dB, significantly enhancing the extraction accuracy of aerodynamic noise signals. Fourth, through precise linkage between a steplessly speed-adjustable low-noise axial flow fan and the impeller-type anemometer, stable testing under different operating conditions (wind speed range of 2-6m / s) is achieved, ensuring the reliability and repeatability of test data. This technical solution improves the signal-to-noise ratio of aerodynamic noise testing of ship ventilation louvers by over 30%, increases noise signal extraction accuracy by 40%, and significantly enhances test data stability. It provides high-precision and high-reliability experimental support for noise characteristic research, noise source analysis, and low-noise structure optimization of ship ventilation louvers, significantly improving the engineering application level of ship cabin noise control.

[0115] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.

[0116] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. An anechoic chamber experimental apparatus for testing the aerodynamic noise of ship ventilation louvers, characterized in that, It includes, A reverberation chamber provides a sound field. The main body of the anechoic chamber is lined with ultra-structural sound-absorbing material on its inner walls, and the side walls have connection ports to connect with the reverberation chamber to provide an acoustic testing environment free from external noise interference. An external air supply system, which is installed in the reverberation chamber, includes a stepless speed-regulating low-noise axial flow fan that provides continuously adjustable airflow and an aluminum foil air guide duct, wherein the aluminum foil air guide duct connects the low-noise axial flow fan and the louver test stand. The sound-absorbing and sound-insulating component includes a sound-insulating sleeve fitted onto an aluminum foil air duct, and a super-structured sound-absorbing material and sound-insulating cotton filling the connection between the main body of the reverberation chamber and the anechoic chamber. The outer wall of the sound-insulating sleeve is wrapped with pipe sound-insulating cotton and damping cloth, and the inner wall is bonded with sound-absorbing cotton between the aluminum foil air duct to form a double sound-insulating and sound-absorbing structure. The louver test stand is located inside the main body of the anechoic chamber and downstream of the air outlet of the external air supply system. The height of the louver test stand is adjustable and it can fix the ventilation louvers of the ship to be tested. An impeller-type anemometer is installed between the air outlet of the external air supply system and the louver test platform, as well as at the louver outlet, to monitor the airflow velocity entering and exiting the louvers in real time. An acoustic testing system is installed inside the main body of the anechoic chamber. The acoustic testing system includes a microphone, a microphone array, a data acquisition system, and a data processing system. The microphone and microphone array are installed at different measurement points in front of and behind the louvered test stand to simultaneously acquire acoustic signals from multiple measurement points. The data acquisition system is connected to the microphone to simultaneously acquire acoustic signals from multiple measurement points. The data processing system is communicatively connected to the data acquisition system and is used for noise signal acquisition and analysis.

2. The anechoic chamber experimental apparatus for testing the aerodynamic noise of ship ventilation louvers as described in claim 1, characterized in that, Preferably, the inner side of the sound insulation sleeve is a vibration damping sheet with a thickness of 5mm that is pasted on the outer wall of the aluminum foil air duct; the outer sound insulation cotton is 20mm thick high-density cotton with added cotton and rubber; the aluminum foil air duct, damping sheet and outer sound insulation cotton are bonded together by adhesive backing, and the outermost sound insulation cotton is fixed with cable ties.

3. The anechoic chamber experimental apparatus for testing the aerodynamic noise of ship ventilation louvers as described in claim 1, characterized in that, The superstructure sound-absorbing material is filled close to the sound insulation sleeve, and the remaining gap inside the connection is filled with sound insulation cotton. At the same time, 50mm thick sound insulation cotton is pasted on both sides of the connection to form a gradient noise reduction structure.

4. The anechoic chamber experimental apparatus for testing the aerodynamic noise of ship ventilation louvers as described in claim 1, characterized in that, The microphone array adopts a 1×7 channel structure, with an adjacent microphone spacing of 0.1m. The array is arranged at a fixed distance on both sides of the louver, and the distance between a single microphone measuring point and the louver outlet is ≥0.15m.

5. The anechoic chamber experimental apparatus for testing the aerodynamic noise of ship ventilation louvers as described in claim 1, characterized in that, The low-noise axial flow fan has a 120° manual vertical rotation at the air outlet, uses a 35° angled fan blade, and has a 2mm thickened steel plate outer shell. The diameter of the fan blade is determined according to the connected aluminum foil air guide duct.

6. The anechoic chamber experimental apparatus for testing the aerodynamic noise of ship ventilation louvers as described in claim 1, characterized in that, The aluminum foil air duct is made of flame-retardant aluminum foil with a thickness of ≥0.2mm. The duct diameter is compatible with the air outlet of the low-noise axial flow fan and the test louvers. The length meets the installation requirements of connecting one end to the axial flow fan in the reverberation room and extending the other end to the fully anechoic indoor louver test platform.

Images