A method for compiling a noise loading spectrum or environmental spectrum profile of a naval gun

Abstract

The application provides a method for compiling a noise load spectrum or an environmental spectrum of a naval gun, comprising: constructing a gun cabin simulation cabin section for naval gun noise testing, setting a plurality of noise sensors and / or pulsating pressure sensors on the surface of the gun cabin simulation cabin section at positions representing cabin equipment in the gun cabin simulation cabin section and positions representing the gun cabin skin; acquiring noise testing data when the naval gun is fired through the plurality of noise sensors and / or pulsating pressure sensors; acquiring noise testing data when the naval gun is fired through a plurality of noise sensors and / or pulsating pressure sensors representing the same position, processing the noise testing data to obtain total sound pressure level noise testing data, and obtaining noise induction data by data induction according to the total sound pressure level noise testing data; and statistically representing the distribution of noise data at the same position, calculating the average, maximum and minimum values of multiple measurements at the measuring point, and obtaining the noise load spectrum or the noise environmental spectrum representing the same position.

Description

Technical Field

[0001] This application belongs to the field of acoustic technology, and specifically relates to a method for compiling the noise load spectrum or environmental spectrum of an aircraft gun. Background Technology

[0002] The "GJB 67.8A-2008 Military Aircraft Structural Strength Specification Part 8: Vibration and Aeroacoustic Durability" stipulates that design requirements should include: acoustic and vibration durability testing should be conducted on newly designed aircraft components or parts that are subjected to forced vibration or strong noise but for which sufficient data is lacking to predict their acoustic and vibration responses. The acoustic and vibration load spectrum of the aircraft structure should be compiled based on the noise and vibration load values ​​experienced by the structure and their corresponding frequency ranges, as well as the time elapsed under the acoustic and vibration loads. Where conditions permit, the "flight state-time" spectrum, "flight state-noise load" spectrum, and "noise load-time" spectrum should be obtained sequentially based on the noise and vibration environment test data from various flight mission profiles, and then synthesized to obtain the noise load spectrum diagram, i.e., the noise load spectrum. Where conditions do not permit, during the design phase, the noise and vibration load spectrum can be compiled using engineering prediction methods, referring to the noise and vibration environment test results and noise or vibration load spectra of similar aircraft.

[0003] During different flight missions, military aircraft experience varying vibration and noise loads on different structural parts. Taking cannon firing as an example, the vibration and noise loads generated by cannon firing act simultaneously on the aircraft's fuselage structure and are transmitted through multiple paths, such as equipment supports and air radiation, to nearby equipment, potentially causing damage to the fuselage structure and surrounding equipment. After a certain type of aircraft completed a live-fire cannon mission, inspection revealed various forms of damage to the fuselage structure, equipment near the cannon, and equipment mounting structures on eight aircraft near frames 10 to 13. Analysis of the causes of vibration and noise problems induced by cannon firing revealed that one major reason was the inadequate standardization of the artillery vibration testing.

[0004] The accuracy of vibration or noise spectrum compilation is of great significance to aircraft structure and airborne equipment because:

[0005] a) If the vibration or noise spectrum is too severe, the development cost of the aircraft, including the main engine and auxiliary engines, will be greatly increased, the difficulty will be increased, and the cycle will be longer. However, the vibration environment in actual use is not like this, which will result in a waste of manpower, material resources, economy and time.

[0006] b) If the intensity of the vibration or noise spectrum is insufficient, it may cause malfunctions, failures or even damage to the main engine (structure) or auxiliary equipment of the aircraft during actual use. In severe cases, it may lead to the destruction of the aircraft and loss of life, resulting in a major accident.

[0007] Therefore, compiling a reasonable vibration or noise load environmental spectrum is directly related to the rationality and reliability of the dynamic strength design of aircraft structures and airborne equipment. Dynamic environmental data is crucial for design and testing. Without this data, it is impossible to form a more reasonable design and verification test, which may lead to over-design, ultimately resulting in increased structural costs and weight, or under-design, ultimately resulting in reduced structural reliability and shortened service life. Summary of the Invention

[0008] The purpose of this application is to provide a method for compiling the noise load spectrum or environmental spectrum of an aircraft gun, so as to solve or mitigate at least one problem in the background art.

[0009] The technical solution of this application is: a method for compiling the noise load spectrum or environmental spectrum shape of an aircraft gun, including:

[0010] Construct a gun cabin simulation section for gun noise testing, characterize the position of the equipment inside the gun cabin within the gun cabin simulation section and / or set multiple noise sensors and / or pulsating pressure sensors on the surface of the gun cabin simulation section characterizing the position of the gun cabin skin, and obtain noise test data of the gun during firing through multiple noise sensors and / or pulsating pressure sensors.

[0011] Noise test data during gun firing is obtained by using multiple noise sensors and / or pulsating pressure sensors at the same location, and the noise test data is processed to obtain total sound pressure level noise test data. Noise summary data is obtained by summarizing the total sound pressure level noise test data.

[0012] The distribution of noise data at the same location is statistically characterized. The average, maximum, and minimum values ​​of multiple measurements at the measuring point are calculated to obtain the noise load spectrum or noise environment spectrum representing the same location.

[0013] In a preferred embodiment of this application, an upper support and a lower support are fixedly connected inside the gun cabin simulation section. Several equipment mounting boxes for simulating equipment inside the cabin are arranged on the upper and lower supports, and the noise sensor is located near the equipment mounting boxes.

[0014] In a preferred embodiment of this application, the process of processing noise data to obtain total sound pressure level noise test data includes load spectrum preprocessing, task mixing, fast Fourier transform, and noise load acquisition, wherein:

[0015] Load spectrum preprocessing includes spurious reading removal and invalid amplitude deletion;

[0016] According to the test outline, the data of each test condition and measurement point are collected, and the data of similar conditions are merged to achieve task mixing.

[0017] Frequency domain data for each working condition and each measuring point is obtained by using the peak-to-average method of time-domain data. The peak noise of each frequency during the firing time of the cannon can be obtained by using the peak-to-average method of time-domain data.

[0018] The noise frequency domain spectrum under different cannon firing conditions is obtained by using the envelope method, thus realizing the acquisition of noise load.

[0019] In a preferred embodiment of this application, during the process of obtaining noise summarization data from total sound pressure level noise test data, for multiple measurements of the same measurement point under the same typical flight condition, the upper confidence limit of the measurement point data is estimated with a 90% confidence level using the following formula:

[0020]

[0021] In the formula: A γ This represents the upper confidence limit of the population mean of the measured values ​​when the confidence level is γ.

[0022] The arithmetic mean of m measurements;

[0023] s is the standard deviation of m measurements;

[0024] m represents the number of measurements;

[0025] t m-1,α / 2 This is the lookup value for the t-distribution table, where α = 0.1;

[0026] For measurements taken less than 5 times, the arithmetic mean shall be used.

[0027] The upper confidence limit of multiple measurements and the calculated average value are used as a single quantity for the flight state in the induction.

[0028] In a preferred embodiment of this application, when statistically analyzing the distribution of noise data at the same location, the method further includes:

[0029] Determine whether the total sound pressure level of each measuring point is equivalent. If it is equivalent, calculate the average, maximum, and minimum values ​​of multiple measurements at each measuring point to obtain the noise load spectrum at the same location.

[0030] If they are not comparable, then according to the conservative principle, select data with a total noise sound pressure level above the predetermined value, and take the average, maximum, and minimum values ​​of multiple sets of measurement data to obtain the noise load spectrum at the same location; or

[0031] If they are not comparable, then according to the principle of maximum value, determine the maximum value of the total sound pressure level, and take the average, maximum and minimum values ​​of multiple measurements to obtain the noise load spectrum at the same location.

[0032] The method for compiling the spectrum shape of gun noise load provided in this application is designed for the characteristics of gun firing noise load as a non-stationary impact signal. By adopting the peak-to-average data processing method of time-domain data, the frequency domain data of each moment in the time period is given by short-time Fourier transform for the noise time-domain data at each moment. Then, the impact response spectrum in the time period is obtained by the envelope method, and finally converted into a 1 / 3 octave band noise spectrum, thereby obtaining the spectrum shape of gun fire noise load. Attached Figure Description

[0033] To more clearly illustrate the technical solutions provided in this application, the accompanying drawings will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application.

[0034] Figure 1 The flowchart is for the method of compiling the gun noise load / environment spectrum of this application.

[0035] Figure 2 This is a schematic diagram of a noise test of the cannon and compartment in one embodiment of this application.

[0036] Figure 3 This is a schematic diagram of the upper and lower support structures within the compartment in this embodiment of the application.

[0037] Figure 4 This is a schematic diagram showing the location of the device mounting box on the upper bracket in this embodiment of the application.

[0038] Figure 5 This is a schematic diagram showing the location of the device mounting box on the lower support in this embodiment of the application.

[0039] Figure 6 This is a schematic diagram showing the locations of the sensors on the inner and outer surfaces of the compartment in this embodiment of the application.

[0040] Figure 7 This is a schematic diagram of the short-time Fourier transform of measurement point M2 at time 1 in this embodiment of the present application.

[0041] Figure 8 This is a schematic diagram of the short-time Fourier transform of measurement point M2 at time 2 in this embodiment of the present application.

[0042] Figure 9 This is the impact response spectrum of measuring point M2 in this embodiment of the application within a 700ms time period.

[0043] Figure 10 This is the 1 / 3 octave band noise spectrum of measurement point M2 in this embodiment of the application within a 700ms time period.

[0044] Figure 11 This is a noise data distribution diagram near the upper device mounting box in this embodiment of the application.

[0045] Figure 12 This is a noise data distribution diagram near the lower-level device mounting box in this embodiment of the application.

[0046] Figure 13 This is the noise environment spectrum near the equipment installation box inside the compartment in this embodiment of the application.

[0047] Figure 14 This is a noise distribution diagram near the muzzle on the inner surface of the compartment in this embodiment of the application.

[0048] Figure 15 This is the noise environment spectrum near the gun muzzle on the inner surface of the compartment in this embodiment of the application.

[0049] Figure 16 This is a noise distribution diagram near the gun muzzle on the outer surface of the compartment in this embodiment of the application.

[0050] Figure 17 This is the noise environment spectrum near the gun muzzle on the inner surface of the compartment in this embodiment of the application.

[0051] Figure 18 This is the common spectral shape of artillery-induced vibration in relevant standards. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings.

[0053] This application proposes a method for compiling the load spectrum of artillery guns that is tailored to the characteristics of artillery noise loads. This method, targeting the characteristics of the firing noise load of aircraft cannons (hereinafter referred to as aircraft cannons), obtains the noise peak value of each frequency during the firing time period of the aircraft cannon by preprocessing the gun sound load data, performing task mixing, fast Fourier transform, and noise load acquisition. The impact response spectrum during the firing time period of the aircraft cannon is obtained by the envelope method, and finally the frequency domain spectrum of artillery noise is obtained.

[0054] like Figure 1 As shown, the method for compiling the cannon noise load spectrum shape provided in this application specifically includes the following steps:

[0055] 1) Construct a gun compartment simulation section (hereinafter referred to as the section) for gun noise testing. Place multiple noise sensors and / or pulsating pressure sensors near the surface of the section that characterize the position of the equipment inside the section and / or the position of the gun compartment skin. Obtain noise test data during gun firing through multiple noise sensors and / or pulsating pressure sensors.

[0056] like Figure 2The diagram shown is a noise test diagram of the 30-4 type aircraft gun and its gun compartment simulation section under continuous firing conditions according to an embodiment of this application. The upper support 21 and the lower support 22 are fixedly connected inside the section 20.

[0057] like Figure 3 As shown, the upper support 21 includes several longitudinally extending upper mounting frames 211A-211D and several laterally extending upper mounting brackets 212A-212C. The lower support 22 includes several longitudinally extending lower mounting frames 221A-221D and several laterally extending lower mounting brackets 222A-222B. Equipment mounting boxes 23A-23G of the simulated cabin equipment are mounted on the upper support 21 and the lower support 22. In this embodiment, there are seven equipment mounting boxes 23A-23G: four equipment mounting boxes 23A-23D are mounted on the upper support 21, and three equipment mounting boxes 23E-23G are mounted on the lower support 22.

[0058] like Figure 4 and Figure 5 The diagram shows the arrangement of noise microphone measurement points for the equipment mounting boxes in this embodiment of the application (the circles indicate the noise microphones). A high-intensity noise microphone M1 to M7 is respectively installed near the equipment mounting boxes 23A to 23D on the upper support 21 and the equipment mounting boxes 23E to 23G on the lower support 22 to test the noise near the equipment mounting boxes 23A to 23G inside the cabin.

[0059] like Figure 6 As shown in this embodiment of the application, multiple high-intensity noise microphones are also arranged on the inner side of the section surface near the gun muzzle 11 to test the noise near the gun muzzle 11 on the inner side of the section. Simultaneously, since the noise on the outer side of the section skin is significantly greater than the noise inside the section, to ensure accurate measurement of the test noise, multiple pulsating pressure sensors are arranged on the outer side of the section surface near the gun muzzle to test the pulsating pressure near the gun muzzle. The measured pulsating pressure can be converted into noise data.

[0060] 2) The noise test data acquired by multiple noise sensors and / or pulsating pressure sensors representing the same location during gun firing are processed to obtain total sound pressure level noise test data. Based on the total sound pressure level noise test data, the noise summary data is obtained by summarizing the data.

[0061] In this application, the process of processing noise data to obtain total sound pressure level noise test data includes load spectrum preprocessing, task mixing, fast Fourier transform, and noise load acquisition.

[0062] Load spectrum preprocessing includes spurious reading removal and invalid amplitude deletion. Spurious readings mainly manifest as: sudden changes exceeding the extreme range of possible parameter changes, unreasonable trends in the changes of related parameters, and data disorder in certain time periods. Spurious readings are generally caused by the test system itself. For example, the introduction of noise interference signals often increases the actual load amplitude. Therefore, spurious readings need to be removed during load spectrum processing.

[0063] The task mixing process is as follows: according to the test outline, the data of each test condition and measurement point are statistically analyzed, and the data of similar conditions are merged.

[0064] The Fast Fourier Transform process is as follows: the frequency domain data of each working condition and each measuring point is obtained by using the peak-to-average method of time domain data. The noise peak value of each frequency during the firing time of the cannon can be obtained by using the peak-to-average method of time domain data.

[0065] The noise load acquisition process is as follows: using the envelope method, the noise frequency domain spectrum is given under different cannon firing conditions.

[0066] In this application, during the process of obtaining noise summarization data based on total sound pressure level noise test data, the determination is made in accordance with "GJB67.8A-2008 Part 8: Vibration and Airborne Acoustic Durability 4.1.4 Amendment": After completing ground and flight tests for airborne acoustics and vibration, the expected load environment differs significantly from the measured environment. Provided sufficient data is available, the maximum expected environmental value should be determined using parametric statistical methods based on the test data. The maximum expected environment should be determined such that, with at least a 90% confidence level, a value equal to or greater than 95% is obtained.

[0067] Specifically, under the same typical flight condition and at the same measurement point, for data from multiple measurements, the upper confidence limit of the data at that measurement point is estimated using a 90% confidence level, calculated as shown in Formula 1. For measurements less than 5 times, the arithmetic mean is taken. The calculation result is used as a single value for that flight condition in the generalization.

[0068]

[0069] In the formula: A γ This represents the upper confidence limit of the population mean of the measured values ​​when the confidence level is γ.

[0070] The arithmetic mean of m measurements;

[0071] s is the standard deviation of m measurements;

[0072] m represents the number of measurements;

[0073] t m-1,α / 2 This is the lookup value for the t-distribution table, where α = 0.1.

[0074] In the "Noise Load-Time" spectrum, in addition to the noise spectrum shape, the duration of the noise load also needs to be set. The duration can be set according to Appendix D of "GJB150.20A Military Equipment Laboratory Environmental Test Methods Part 20: Artillery Vibration Test":

[0075] a) The conservatively estimated duration is the longest duration of the shelling during each flight multiplied by the expected number of takeoffs and landings of the shelling project;

[0076] b) The longest firing time for each flight is equal to the total shell load of each aircraft divided by the firing rate of that aircraft.

[0077] c) The number of takeoffs and landings for artillery fire is related to flight planning, training, and combat utilization, and is generally around 200 to 300.

[0078] For example, in this embodiment of the application, there are seven equipment mounting boxes 23A to 23G that characterize the installation position of the equipment inside the cabin, and there are seven corresponding measurement points M1 to M7. When analyzing the noise test data of the seven measurement points M1 to M7, a 700ms time period is selected. By comparing the data results of repeated tests, data with more spikes and data that have not returned to zero are removed.

[0079] by Figure 7 and Figure 8 Taking the test data at two time points shown as an example, the frequency domain data at the two time points within a 700ms time interval are obtained through short-time Fourier transform, and then the impulse response spectrum for the 700ms time interval is obtained using the envelope method, as shown. Figure 9 As shown, it is finally converted into a 1 / 3 octave band noise spectrum, as follows. Figure 9 As shown, the total sound pressure level test data of the measuring point is obtained based on the 1 / 3 octave band noise spectrum.

[0080] Repeating the above process, for the noise time-domain data at each moment, 1 / 3 octave band frequency-domain data is provided to obtain the total sound pressure level test data for all measurement points of the equipment mounting box. For example, in this embodiment of the application, a total of 17 noise measurements were performed on measurement points M1-M7 of the equipment mounting box. The total sound pressure level test data of the 17 measurements are shown in Table 1. Finally, based on the multiple measurement results of each measurement point and the calculation formula of the upper limit of confidence under the confidence level, the noise data summary results of each measurement point at 90% confidence level are obtained, as shown in Table 2.

[0081] Table 1 Noise test data near the equipment mounting box inside the cabin.

[0082]

[0083] Table 2. Summary of Noise Data Near In-cabin Equipment Installation Boxes

[0084]

[0085]

[0086] Similarly, in this embodiment of the application, 12 noise sensors are set near the muzzle on the inner side of the section surface representing the position of the gun compartment skin to form measurement points M11 to M43. When analyzing the noise test data of the 12 measurement points, a 700ms time period is selected, and the data results of repeated tests are compared. Data with more burrs or not zeroed out are removed.

[0087] Similarly, for the noise time-domain data at each moment, 1 / 3 octave band frequency-domain data are provided to obtain the total sound pressure level test data of all measuring points near the gun muzzle on the inner side of the compartment surface. For example, in this embodiment of the application, a total of 16 noise measurements were performed on each measuring point M11-M43. The total sound pressure level results of the 16 measurements are shown in Table 3. Finally, based on the multiple measurement results of each measuring point and the calculation formula of the upper limit of confidence under the confidence level, the 90% confidence level data summary results of each measuring point are shown in Table 4.

[0088] Table 3 Noise test data near the muzzle on the inner surface of the compartment.

[0089]

[0090]

[0091] Table 4. Summary of Noise Data Near the Gun Muzzle on the Inner Surface of the Compartment Section

[0092]

[0093] Similarly, in this embodiment of the application, 16 pulsating pressure sensors are arranged near the muzzle on the outer side of the section surface representing the gun compartment skin position, forming measurement points M11 to M44 for noise test data. Since the noise load near the muzzle on the outer side of the section surface is relatively large, it is difficult to measure with a conventional microphone. Therefore, this application uses pulsating pressure sensors to test the pulsating pressure data and converts it into noise data. When analyzing the pulsating pressure test data from the 16 measurement points, a 700ms time period is selected, and the results of repeated tests are compared, discarding data with many spikes or that do not reach zero.

[0094] For the noise time-domain data at each moment, 1 / 3 octave band frequency-domain data are provided to obtain the total sound pressure level test data of all measuring points near the gun muzzle on the outer surface of the compartment. For example, in this embodiment of the application, a total of 7 measurements were performed at each measuring point P11-P44. The total sound pressure level results of the 7 measurements are shown in Table 5. Based on the multiple measurement results of each measuring point and the calculation formula of the upper limit of confidence under the confidence level, the 90% confidence level data summary results of each measuring point are shown in Table 6.

[0095] Table 5 Noise test data near the gun muzzle on the outer surface of the compartment.

[0096]

[0097]

[0098] Table 6 Summary of Noise Data Near the Gun Muzzle on the Outer Surface of the Cabin Section

[0099]

[0100] 3) Statistically analyze the distribution of noise data at the same location, calculate the average, maximum, and minimum values ​​of multiple measurements at the measuring point, and obtain the noise load spectrum or noise environment spectrum at the same location.

[0101] When statistically analyzing the noise data distribution at the same location, the system first determines whether the total sound pressure level of each measuring point is comparable. If they are comparable, the average, maximum, and minimum values ​​of multiple measurements at each measuring point are calculated to obtain the noise load spectrum at the same location. If they are not comparable, data with a total sound pressure level above a predetermined value are selected based on a conservative principle, and the average, maximum, and minimum values ​​of multiple sets of measurement data are taken to obtain the noise environment spectrum near the gun muzzle on the inner surface of the compartment. Alternatively, based on the maximum value principle, the maximum value of the total sound pressure level is determined, and the average, maximum, and minimum values ​​of multiple measurements are taken to give the noise load spectrum near the gun muzzle outside the compartment.

[0102] For example, in this embodiment of the application, based on the above noise test data, the noise spectrum of the Type 30-4 cannon is divided into three categories: noise load / environment spectrum near the equipment installation box inside the compartment, noise load / environment spectrum near the muzzle on the inner surface of the compartment, and noise load / environment spectrum near the muzzle on the outer surface of the compartment.

[0103] For the noise environment spectrum near the equipment mounting boxes inside the compartment, the noise data distribution near equipment mounting boxes M1-M7 inside the compartment was statistically analyzed, such as... Figure 11 and Figure 12 The diagram shows the measurement points for the upper and lower equipment mounting boxes. As can be seen from the diagram, the total sound pressure level is roughly equivalent between measurement points M1 to M7. Therefore, by taking the average, maximum, and minimum values ​​from multiple measurements at each measurement point, the noise load / environmental spectrum near the equipment mounting boxes inside the compartment is obtained. Figure 13 As shown in Table 7.

[0104] Table 7 Noise Environmental Spectrum Near In-cabin Equipment Installation Boxes

[0105]

[0106]

[0107] Depend on Figure 13As can be seen from the noise environment spectrum near the equipment installation box inside the compartment shown in Table 7, the noise environment spectrum near the equipment installation box inside the compartment is composed of a broadband random noise spectrum and a sinusoidal discrete spectrum. The center frequencies of the 1 / 3 octave band of the sinusoidal discrete spectrum are 25Hz, 50Hz, 80Hz, and 160Hz, which correspond to the fundamental frequency and harmonic frequency of the artillery firing frequency.

[0108] In this embodiment of the application, for the noise environment spectrum near the gun muzzle on the inner surface of the compartment, the distribution of noise data near the gun muzzle on the inner surface of the compartment is statistically analyzed, such as... Figure 14 The diagram shows the noise distribution near the gun muzzle on the inner surface of the compartment. The total sound pressure level at measuring points M31, M32, and M41 is less than 160 dB, while the total sound pressure level at the other measuring points is roughly the same. Therefore, a conservative approach was adopted when compiling the noise environment spectrum, using data with a total sound pressure level above 160 dB. The average, maximum, and minimum values ​​of multiple sets of measurements were then used to obtain the noise environment spectrum near the gun muzzle on the inner surface of the compartment. Figure 15 As shown in Table 8.

[0109] Table 8 Noise Spectrum Near the Gun Muzzle Inside the Cabin

[0110]

[0111]

[0112] Depend on Figure 15 As shown in Table 8, the noise environment spectrum near the gun muzzle on the inner surface of the compartment is composed of a broadband random noise spectrum and a sinusoidal discrete spectrum. The center frequencies of the 1 / 3 octave band of the sinusoidal discrete spectrum are 25 Hz and 50 Hz, respectively, which correspond to the fundamental frequency and harmonic frequency of the firing frequency.

[0113] In this embodiment of the application, for the noise load spectrum near the gun muzzle on the outer surface of the compartment, the distribution of noise data near the gun muzzle on the outer surface of the compartment is statistically analyzed, such as... Figure 16 The diagram shows the noise distribution near the gun muzzle on the outer surface of the compartment. Point P33, with the highest total sound pressure level, was selected. The average, maximum, and minimum values ​​from multiple measurements were taken to obtain the noise load spectrum near the gun muzzle. Figure 17 As shown in Table 9.

[0114] Table 9 Noise Load Spectrum Near the External Gun Muzzle

[0115]

[0116]

[0117] Depend on Figure 17As can be seen from the noise load spectrum near the gun muzzle on the outer surface of the compartment shown in Table 9, the noise load spectrum near the gun muzzle on the outer surface of the compartment is composed of a broadband random noise spectrum and a sinusoidal discrete spectrum. The center frequencies of the 1 / 3 octave band of the sinusoidal discrete spectrum are 25Hz and 50Hz, respectively, which correspond to the fundamental frequency and harmonic frequency of the firing frequency.

[0118] The method for compiling the spectrum shape of gun noise load provided in this application is designed for the characteristics of gun firing noise load as a non-stationary impact signal. By adopting the peak-to-average data processing method of time-domain data, the frequency domain data of each moment in the time period is given by short-time Fourier transform for the noise time-domain data at each moment. Then, the impact response spectrum in the time period is obtained by the envelope method, and finally converted into a 1 / 3 octave band noise spectrum, thereby obtaining the spectrum shape of gun fire noise load.

[0119] This embodiment of the application, based on firing test data from a simulated section of a Type 30-4 aircraft cannon, compiled the noise load spectrum near the muzzle and the noise environment spectrum inside the section. The total sound pressure level of the noise load spectrum was 215.54 dB, and the total sound pressure level of the noise environment spectrum was 160.35 dB. Both spectrum shapes are similar to the general artillery-induced vibration spectrum shape described in Appendix D of "GJB150.20A Military Equipment Laboratory Environmental Test Methods Part 20: Artillery Vibration Test". Figure 18 Similarly, both consist of a broadband random noise spectrum and a sinusoidal discrete spectrum, where the sinusoidal discrete spectrum represents the fundamental frequency and harmonic frequencies of the artillery firing frequency.

[0120] It should be noted that the gun noise load / environment spectrum compilation in this application is based on ground test data. Ground tests differ from aerial tests. During aerial flight tests, the aircraft and gun are in a free field, while in ground tests, the noise from the gun reflects off the ground and surrounding buildings. Therefore, the obtained gun noise / environment spectrum is relatively conservative. The next step can be to continue compiling the gun noise load / environment spectrum based on actual aerial test data, taking into account factors such as flight speed and altitude, to ultimately obtain the gun noise load / environment spectrum under flight conditions.

[0121] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for compiling the noise load spectrum or environmental spectrum shape of an aircraft gun, characterized in that, include: A gun compartment simulation section is constructed for gun noise testing. Multiple noise sensors and / or pulsating pressure sensors are installed on the surface of the gun compartment simulation section, which characterizes the position of the equipment inside the compartment and / or characterizes the position of the gun compartment skin. Noise test data during gun firing is obtained through multiple noise sensors and / or pulsating pressure sensors. An upper support and a lower support are fixedly connected inside the gun compartment simulation section. Several equipment mounting boxes for simulating the equipment inside the compartment are arranged on the upper support and the lower support. The noise sensors are located near the equipment mounting boxes. Noise test data during gun firing is acquired by using multiple noise sensors and / or pulsating pressure sensors at the same location. This data is then processed to obtain total sound pressure level (SPL) noise test data. Based on this SPL noise test data, noise summarization data is obtained. The process of obtaining the total SPL noise test data includes load spectrum preprocessing, task mixing, fast Fourier transform (FFT), and noise load acquisition. Load spectrum preprocessing includes spurious reading removal and invalid amplitude deletion. According to the test outline, data from each test condition and measurement point are statistically analyzed, and data from similar conditions are merged to achieve task mixing. The peak-to-peak averaging method is used to obtain frequency domain data for each condition and measurement point, allowing the noise peak value at each frequency during the gun firing period to be obtained. The envelope method is used to obtain the noise frequency domain spectrum under different gun firing conditions, thus achieving noise load acquisition. The distribution of noise data at the same location is statistically characterized. The average, maximum, and minimum values ​​of multiple measurements at the measuring point are calculated to obtain the noise load spectrum or noise environment spectrum representing the same location.

2. The method for compiling the noise load spectrum or environmental spectrum shape of an aircraft gun as described in claim 1, characterized in that, In the process of obtaining noise summary data based on total sound pressure level noise test data, for multiple measurements at the same measurement point under the same typical flight condition, the following formula is used to estimate the upper confidence limit of the data at that measurement point with a 90% confidence level: In the formula: A γ This represents the upper confidence limit of the population mean of the measured values ​​when the confidence level is γ. The arithmetic mean of m measurements; Let m be the standard deviation of m measurements; m represents the number of measurements; t m-1,α / 2 This is the lookup value from the t-distribution table, α=0.1; For measurements taken less than 5 times, the arithmetic mean shall be used. The upper confidence limit and arithmetic mean of multiple measurements are used as a single value for the flight state in the induction.

3. The method for compiling the noise load spectrum or environmental spectrum shape of an aircraft gun as described in claim 1, characterized in that, When analyzing the distribution of noise data at the same location, the following should also be included: Determine whether the total sound pressure level of each measuring point is equivalent. If it is equivalent, calculate the average, maximum, and minimum values ​​of multiple measurements at each measuring point to obtain the noise load spectrum at the same location. If they are not comparable, then according to the conservative principle, select data with a total noise sound pressure level above the predetermined value, and take the average, maximum, and minimum values ​​of multiple sets of measurement data to obtain the noise load spectrum at the same location; or If they are not comparable, the maximum value of the total sound pressure level is determined according to the principle of maximum value. The average, maximum and minimum values ​​of multiple measurements are then taken to obtain the noise load spectrum at the same location.

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