A method for judging the effectiveness of measuring points of the rotating noise of a hovering intermediate model rotor

Abstract

The present invention belongs to the technical field of rotorcraft rotor noise test, and particularly relates to a method for judging the effectiveness of measuring points of model rotor rotational noise during hovering. The judgment method calculates the reference distance for placing the arc-shaped bracket based on the rotor passing frequency and the speed of sound, places the arc-shaped bracket at multiple different reference distances at the same azimuth angle, conducts horn sound emission and noise collection at 1 to 20 times the reference frequency for the measuring points on the paths with the same azimuth and the same included angle respectively, analyzes the sound attenuation characteristics of the total sound pressure level on the paths with the same azimuth and the same included angle, and gives a judgment result on whether the noise measuring point is effective. This method is closer to the characteristics that the rotor noise is mainly composed of components at 1 to 20 times the passing frequency and the rotor noise at different distances has obvious attenuation characteristics. The judgment method proposed by the present invention has better practical use effects and engineering value.

Description

Technical Field

[0001] The present invention belongs to the technical field of rotor noise test of rotary-wing aircraft, and particularly relates to a method for judging the effectiveness of measurement points of model rotor rotational noise during hover. Background Technique

[0002] Rotor aerodynamic noise is the main source of external noise of rotary-wing aircraft. Studying the sound field distribution characteristics of rotor noise is of guiding significance for whether rotary-wing aircraft can obtain noise airworthiness certification. Reducing rotor noise is the main way to reduce the external noise of rotary-wing aircraft. Due to the characteristics of low frequency, long propagation distance, and slow attenuation of rotor rotational noise, effective measurement of it can provide first-hand experimental data for rotor noise reduction research.

[0003] At present, the experimental research on rotor aerodynamic noise of rotary-wing aircraft is mainly carried out in an open space without obstacles in the outfield or in an anechoic chamber and anechoic wind tunnel with a closed and anechoic environment. That is, its noise test has high requirements for the test environment and test site, but the requirements for the environment and site also limit the development of relevant noise tests on the existing test bench.

[0004] In this field, in the already disclosed technologies, regarding the selection of measurement points for rotor rotation noise, Patent CN114964691A discloses a method for selecting the measurement point positions of the rotor noise field in an anechoic wind tunnel. In this patent, an arc-shaped bracket is arranged in the anechoic wind tunnel, multiple measurement point positions are selected in the arc-shaped bracket, and a microphone is installed at each measurement point position; the microphone coefficient is calibrated on-site using a standard sound source; the background noise data of the anechoic wind tunnel is collected using the microphones at each measurement point position; a sound with a fixed frequency and sound pressure level is emitted using a directional horn, and the sound pressure of the microphones at each measurement point position is collected; the omnidirectional horn is arranged at the hub center position of the rotor test bench; the fixed-frequency sound pressure level analysis is performed on the sound pressure collected at each measurement point position; and the measurement point positions for measuring the rotor noise in the rotor noise field are selected according to the analysis results. The position of the arc-shaped bracket selected in this patent is centered on the hub and at an integer multiple (such as 3R) of the rotor radius R from it. However, the rotor noise is mainly the noise of the rotor passing frequency (rotational speed / second × number of rotor blades), and the wavelength of the noise does not have an integer multiple relationship with the rotor radius R. This placement method will cause a phase deviation in the measured waveform. At the same time, in this patent, the arc-shaped bracket is arranged at several azimuth angles at only one distance position (such as 3R) each time, without considering whether the sound attenuation characteristics at different distances (such as 2R, 3R, 4R) meet the requirements. Moreover, the measurement points are selected in this patent based on the fact that the number of effective measurement points selected on a certain arc-shaped bracket is not less than a preset proportional value of the total number of microphones on the arc-shaped bracket. This method does not consider the influence of the emission noise generated by the different local environments of the microphones at different positions on the arc-shaped bracket due to their different spatial positions on the judgment. Therefore, the measurement point positions of the rotor noise field selected by this method are not the optimal positions for measuring rotor noise. Summary of the Invention

[0005] The object of the present invention: The rotor hover performance test is usually carried out in a hover room. If the hover room is not specifically designed for an anechoic environment, the present invention proposes a method for judging the effectiveness of noise measurement points that is more in line with the actual characteristics of rotor noise to ensure the effectiveness of the rotor rotation noise test data in the complex sound field environment of the hover room; and solve the problem that the conventional noise measurement method cannot accurately obtain the rotor rotation noise data.

[0006] The technical solution of the present invention: A method for judging the effectiveness of the rotor noise measurement points of a hover room model, the effectiveness judgment method includes the following steps:

[0007] Step S1: Calculate the reference distance for arranging the arc-shaped bracket according to the rotor passing frequency and the speed of sound;

[0008] Step S2: Arrange the arc-shaped brackets at multiple different reference distances at the same azimuth angle;

[0009] Step S3: For the measuring points on the paths with the same orientation and the same included angle, perform horn sound emission and noise acquisition at 1 to 20 times the reference frequency.

[0010] Step S4: According to the acquisition results, perform an analysis of the sound attenuation characteristics of the total sound pressure level on the paths with the same orientation and the same included angle, and give a judgment result on whether the noise measuring points are valid.

[0011] Preferably, in step S1, the calculation process of the reference distance for placing the arc-shaped bracket is as follows: Calculate the rotor passing frequency based on the actual working frequency of the rotor and the actual number of installed blade; Combine the sound speed and a certain integer multiple of the frequency to calculate the reference distance of the measuring point.

[0012] Preferably, in step S2, when placing the arc-shaped bracket, first determine the plane of the rotor disk and divide the azimuth angle, and find the first azimuth angle of the plane of the rotor disk; Then, with the hub center as the origin, extend along this azimuth angle to find a position point at a certain distance from the center point, and place multiple arc-shaped brackets in sequence; And evenly install multiple microphones along the arc-shaped rod of each bracket in sequence, and mark each microphone correspondingly.

[0013] Preferably, in step S3, the horn sound emission and noise acquisition are carried out in the following manner;

[0014] The first step: Hang the standard sound source at a certain height directly above the hub center, and the sound source faces the arc-shaped bracket;

[0015] The second step: Power on and preheat the noise measurement system;

[0016] The third step: Start the software of the noise acquisition system, set the sampling frequency, and simultaneously collect the sound pressure data of the background noise;

[0017] The fourth step: Calculate the one-third octave band total sound pressure level of the background noise of each microphone;

[0018] The fifth step: Turn on the sound source to emit a single-frequency sound corresponding to the first integer multiple of the frequency, start the software of the noise acquisition system, and set the same sampling frequency as in the third step;

[0019] The sixth step: Calculate the one-third octave band total sound pressure level of each microphone at this frequency;

[0020] The seventh step: Repeat the fifth step, let the sound source emit a single-frequency sound corresponding to the second integer multiple of the frequency, then collect the sound at this frequency, and repeat the sixth step to calculate the one-third octave band total sound pressure level of each microphone at this frequency;

[0021] The eighth step: Repeat the seventh step, let the sound source emit single-frequency sounds corresponding to the Nth integer multiple of the frequency in sequence, collect and calculate the one-third octave band total sound pressure level of each microphone at each frequency.

[0022] Preferably, in step S4, the analysis of the sound attenuation characteristics of the total sound pressure level on the paths with the same orientation and the same included angle includes the following steps:

[0023] First step, using the background noise data to eliminate the invalid measurement points and paths;

[0024] Second step, analyzing the sound attenuation characteristics on the paths with the same orientation and the same included angle;

[0025] Third step, referring to the second step, respectively and sequentially judging the one-third octave total sound pressure levels of the three measurement points on the path with a 0-degree azimuth and a 0-degree included angle at frequencies F2 to F20 to determine their effectiveness;

[0026] Fourth step, referring to the second step and the third step, respectively and sequentially judging the one-third octave total sound pressure levels of the three measurement points on the paths with a 0-degree azimuth angle and included angles of 10 degrees, 20 degrees, 30 degrees, 40 degrees, 50 degrees, 60 degrees, and 70 degrees at frequencies F 1 ~F 2０ to determine their effectiveness;

[0027] Fifth step, moving the three arc-shaped brackets to the second azimuth angle n angle-1 , and then repeating the horn sound emission and noise collection;

[0028] Sixth step, repeating the fifth step, sequentially moving the three arc-shaped brackets to n angle-2、 n angle-3 …n angle-m ; finally obtaining the effectiveness information of the three measurement points on the paths with frequencies F 1 ~F 2０ and azimuth angles n angle-1、 n angle-2 …n angle-m and included angles of 0 degrees, 10 degrees, 20 degrees, 30 degrees, 40 degrees, 50 degrees, 60 degrees, and 70 degrees.

[0029] Preferably, the specific judgment process for the effectiveness of the noise measurement points includes the following steps:

[0030] Based on obtaining the effectiveness information of the three measurement points on the paths with frequencies F 1 ~F 2０ and azimuth angles n angle-1、 n angle-2 …n angle-m and included angles of 0 degrees, 10 degrees, 20 degrees, 30 degrees, 40 degrees, 50 degrees, 60 degrees, and 70 degrees, further comprehensively judge the effectiveness of the three measurement points on the paths with different azimuths and various included angles to select the azimuth and included angle that are overall available and effective.

[0031] Advantages of the present invention: A method for judging the effectiveness of measurement points of the rotational noise of a hovering model rotor. Based on the rotor passing frequency and the speed of sound, the reference distance for placing the arc-shaped bracket is calculated. The arc-shaped brackets are placed at multiple different reference distances at the same azimuth angle. For the measurement points on the same azimuth and the same included angle path, the horn emits sound and the noise is collected at 1 to 20 times the reference frequency. The sound attenuation characteristics of the total sound pressure level on the same azimuth and the same included angle path are analyzed, and a judgment result on whether the measurement point of the noise is effective is given. This method is closer to the characteristics that the rotor noise is mainly composed of components at 1 to 20 times the passing frequency and the rotor noise at different distances has obvious attenuation characteristics. Therefore, this method has better practical use effects and engineering value. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a flow chart of the method of the present invention;

[0033] Figure 2 It is a schematic diagram of the placement position of the arc-shaped bracket. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0035] The following further describes the present invention in detail.

[0036] (1) Calculate the reference distance for placing the arc-shaped bracket

[0037] The calculation process is as follows:

[0038] First step, according to the rotor operating frequency n rpm (unit: revolutions per minute) specified in the test task book and the number of blade pieces n rotor (unit: piece, generally 3 ≤ n rotor ≤ 7), the rotor passing frequency F 1 = n rpm × n rotor ÷ 60 (F 0 unit: Hertz) is calculated according to the following formula;

[0039] Second step, calculate the octave frequencies of F 2 、F 3 …F n (F 2 、F 3 … F n unit: Hertz), F n = n × nrpm × n rotor ÷ 60, where F n The subscript n is an integer from 2 to 20;

[0040] In the third step, calculate the measured point reference distance D = 340 ÷ F 1 (D 0 (Unit: meter).

[0041] (2) Arrangement of arc-shaped brackets

[0042] The arc-shaped brackets are used for the arrangement of the hovering noise measurement points. The arrangement steps are as follows:

[0043] In the first step, determine the propeller disk plane and divide the azimuth angle: The center of the propeller hub is the center point P0, and the disk plane formed by the rotation of the rotor in the zero-lift state for one circle is the propeller disk plane. The radius of the propeller disk plane is the rotor radius R (unit of R: meter, generally 0.5 ≤ R ≤ 2). The direction from the center of the propeller hub to the tail direction in the propeller disk plane is the +X axis. Rotate around the +X axis with P0 as the center point (in the rotor rotation direction specified in the task book) and divide the propeller disk plane into m azimuth angles n angle at intervals of n degrees, where m = 360 ÷ n angle-0、 n angle-1、 n angle-2 … n angle-m , where m = 360 ÷ n angle .

[0044] n angle is determined according to the rotor radius R, n angle = 20 ÷ R, and n angle is generally a positive multiple of 5. Assume R = 2 below, then n angle = 10. The azimuth angle n angle-90 is the +Y axis.

[0045] In the second step, arrange the arc-shaped brackets: Find the first azimuth angle n angle-0 of the propeller disk plane. Then, with the center of the propeller hub as the origin, extend along this azimuth angle and find the position points at distances of 1D, 1.5D, and 2D from the center point P0, and place 3 arc-shaped brackets with arc radii of 1D, 1.5D, and 2D in sequence. The positions of the 3 arc-shaped brackets are respectively marked as P 1D-0 , P 1.5D-0 , P 2D-0 , and the subscripts "-0" in the marks P 1D-0 , P 1.5D-0 , P 2D-0 represent the azimuth angle, that is, n angle-0 .

[0046] Step 3: Microphone Installation: After the arc-shaped bracket is placed properly, a microphone needs to be installed on the arc-shaped rod of the bracket (it is required that the microphone coefficient be calibrated on-site in advance). The installation positions of the microphones are 0° (this position point is at the same height as the hub center. Assuming the arc-shaped bracket is P 1D-0 , then the microphone position is P 1D-0-0 , where the value after the second "-" in the subscript represents the angle between the line connecting the microphone and the hub center and the propeller disk plane, and the angle here is 0). Then, along the arc-shaped branch, microphones are installed at intervals of 10° downward (in terms of the angle) at P 1D-0-10 , P 1D-0-20 , P 1D-0-30 , P 1D-0-40 , P 1D-0-50 , P 1DR-0-60 , P 1D-0-70 positions. Similarly, microphones can be installed on the arc-shaped rods of P 1.5D-0 and P 2D-0 arc-shaped brackets, and are respectively labeled as P 1.5D-0-0 , P 1.5D-0-10 , P 1.5D-0-20 , P 1.5D-0-30 , P 1.5D-0-40 , P 1.5D-0-50 , P 1.5D-0-60 , P 1.5D-0-70 , P 2D-0-0 , P 2D-0-10 , P 2D-0-20 , P 2D-0-30 , P 2D-0-40 , P 2D-0-50 , P 2D-0-60 , P 2D-0-70 .

[0047] (3) Speaker Sound Emission and Noise Acquisition

[0048] The steps for the fixed-frequency sound emission and acquisition of the sound source are as follows:

[0049] Step 1: Hang the standard sound source 0.2 meters directly above the hub center. At this time, it is best not to install propeller blades on the hub. If the propeller blades cannot be removed, the hub needs to be rotated so that the arc-shaped bracket is in the middle position of the angle between any two adjacent propeller blades.

[0050] Step 2: Power on the noise measurement system and preheat it for at least 15 minutes;

[0051] Step 3: Start the software of the noise acquisition system, set the sampling frequency to 51,200 points per second, and collect the sound pressure data of the background noise for 10 seconds.

[0052] Step 4: Calculate the one-third octave band total sound pressure level of the background noise of each microphone, and label them as N 1D-0-0-0 , N 1D-0-10-0 , N1D-0-20-0 , N 1D-0-30-0 , N 1D-0-40-0 , N 1D-0-50-0 , N 1DR-0-60-0 , N 1D-0-70-0 , N 1.5D-0-0-0 , N 1.5D-0-10-0 , N 1.5D-0-20-0 , N 1.5D-0-30-0 , N 1.5D-0-40-0 , N 1.5D-0-50-0 , N 1.5D-0-60-0 , N 1.5D-0-70-0 , N 2D-0-0-0 , N 2D-0-10-0 , N 2D-0-20-0 , N 2D-0-30-0 , N 2D-0-40-0 , N 2D-0-50-0 , N 2D-0-60-0 , N 2D-0-70-0 , the 0 after the third "-" in the subscript of the identifier represents background noise;

[0053] Step 5: Turn on the sound source to emit a single-frequency sound with a frequency of F1 and a sound pressure level of 114 dB. Start the software of the noise acquisition system, set the sampling frequency to 51,200 points per second, and collect the sound at this frequency for 10 seconds;

[0054] Step 6: Calculate the overall sound pressure level of each microphone in one-third octave bands at this frequency, and label them as N 1D-0-0-F1 , N 1D-0-10-F1 , N 1D-0-20- F1 , N 1D-0-30- F1 , N 1D-0-40-F1 , N 1D-0-50- F1 , N 1DR-0-60- F1 , N 1D-0-70- F1 , N 1.5D-0-0- F1 , N 1.5D-0-10- F1 , N 1.5D-0-20- F1 , N 1.5D-0-30- F1 , N 1.5D-0-40- F1 , N 1.5D-0-50- F1 , N 1.5D-0-60- F1 , N 1.5D-0-70- F1 , N 2D-0-0- F1 , N 2D-0-10- F1 , N 2D-0-20- F1 , N 2D-0-30- F1 , N 2D-0-40- F1 , N 2D-0-50- F1 , N 2D-0-60- F1 , N 2D-0-70- F1 , the F1 after the third "-" in the subscript of the identifier represents collecting the sound at the F1 frequency.

[0055] Step 7: Repeat Step 5, and let the sound source emit a frequency of F 2, a single-frequency sound with a sound pressure level of 114 dB, then collect the sound at this frequency for 10 seconds, and then repeat the sixth step to calculate the overall sound pressure level of each microphone in one-third octave bands at this frequency.

[0056] Step 8: Repeat Step 7, and let the sound source emit sounds with frequencies of F 3 … F 20 in sequence, collect and calculate the overall sound pressure level of each microphone in one-third octave bands at each frequency.

[0057] (4) Analysis of the sound attenuation characteristics of the measuring points on the paths with the same azimuth and the same included angle

[0058] The steps for analyzing the sound attenuation characteristics on the paths with the same azimuth and the same included angle are as follows:

[0059] Step 1: Use the background noise data to eliminate invalid measuring points and paths: First, for the overall sound pressure levels N

[0060] in one-third octave bands of the background noise of each microphone obtained in the fourth step of (3). 1D-0-0-0 、N 1D-0-10-0 、N 1D-0-20-0 、N 1D-0-30-0 、N 1D-0-40-0 、N 1D-0-50-0 、N 1DR-0-60-0 、N 1D-0-70-0 、N 1.5D-0-0-0 、N 1.5D-0-10-0 、N 1.5D-0-20-0 、N 1.5D-0-30-0 、N 1.5D-0-40-0 、N 1.5D-0-50-0 、N 1.5D-0-60-0 、N 1.5D-0-70-0 、N 2D-0-0-0 、N 2D-0-10-0 、N 2D-0-20-0 、N 2D-0-30-0 、N 2D-0-40-0 、N 2D-0-50-0 、N 2D-0-60-0 、N 2D-0-70-0 calculate the mean value N E-0-0 and the standard deviation D iff-0-0 ,N E-0-0 =( N 1D-0-0-0 +N 1D-0-10-0 +N 1D-0-20-0 +N 1D-0-30-0 +N 1D-0-40-0 +N 1D-0-50-0 +N 1DR-0-60-0 +N 1D-0-70-0 +N 1.5D-0-0-0 +N 1.5D-0-10-0 +N 1.5D-0-20-0 +N 1.5D-0-30- +N 1.5D-0-40-0 +N 1.5D-0-50-0 +N1.5D-0-60-0 +N 1.5D-0-70-0 +N 2D-0-0-0 +N 2D-0-10-0 +N 2D-0-20-0 +N 2D-0-30-0 +N 2D-0-40-0 +N 2D-0-50-0 +N 2D-0-60-0 +N 2D-0-70-0 )÷24, D iff-0-0 =SQRT(((N 1D-0-0-0 - N E-0-0 )^2+(N 1D-0-10-0 - N E-0-0 )^2+(N 1D-0-20-0 - N E-0-0 )^2+(N 1D-0-30-0 - N E-0-0 )^2+(N 1D-0-40-0 - N E-0-0 )^2+(N 1D-0-50-0 - N E-0-0 )^2+(N 1DR-0-60-0 - N E-0-0 )^2+(N 1D-0-70-0 - N E-0-0 )^2+(N 1.5D-0-0-0 - N E-0-0 )^2+(N 1.5D-0-10-0 - N E-0-0 )^2+(N 1.5D-0-20-0 - N E-0-0 )^2+(N 1.5D-0-30-0 - N E-0-0 )^2+(N 1.5D-0-40-0 - N E-0-0 )^2+(N 1.5D-0-50-0 - N E-0-0 )^2+(N 1.5D-0-60-0 - N E-0-0 )^2+(N 1.5D-0-70-0 - N E-0-0 )^2+(N 2D-0-0-0 - N E-0-0 )^2+(N 2D-0-10-0 - N E-0-0 )^2+(N 2D-0-20-0 - N E-0-0 )^2+(N 2D-0-30-0 - N E-0-0 )^2+(N 2D-0-40-0 - N E-0-0 )^2+(N 2D-0-50-0 - N E-0-0 )^2+(N 2D-0-60-0 - N E-0-0 )^2+(N 2D-0-70-0 - NE-0-0 )^2) ÷ 24; Then judge whether the absolute value of the difference between the overall sound pressure of each microphone's background noise in one-third octave bands and N E-0-0 is greater than 3 times the standard deviation D iff-0-0 . If so, consider the measurement point as invalid, and at the same time, the measurement points at the same angles of the other two arc-shaped branches corresponding to this measurement point are also considered invalid.

[0061] Second step, analysis of sound attenuation characteristics on paths with the same azimuth and the same included angle: Assume that the overall sound pressure levels N 1 in one-third octave bands of the three measurement points collected on the path with 0 azimuth and 0 included angle at frequency F 1D-0-0-F1 , N 1.5D-0-0-F1 and N 2D-0-0-F1 are taken as an example. If both 1.5 ≤ N 1.5D-0-0-F1 - N 1D-0-0-F1 ≤ 2 and 1.0 ≤ N 2D-0-0-F1 - N 1.5D-0-0-F1 ≤ 1.5 are satisfied, it indicates that the three measurement points on the path with 0 azimuth and 0 included angle at frequency F1 and the sound attenuation characteristics of this path meet the requirements, and the sound pressure level data are valid; otherwise, the sound pressure level data of the three measurement points on the path with 0 azimuth and 0 included angle at frequency F1 are invalid.

[0062] Third step, referring to the second step, judge the overall sound pressure levels in one-third octave bands of the three measurement points on the path with 0-degree azimuth and 0-degree included angle at frequencies F 2 ~F 2０ in turn to determine their validity.

[0063] Fourth step, referring to the second step and the third step, judge the overall sound pressure levels in one-third octave bands of the three measurement points on the paths with 0-degree azimuth angle and included angles of 10 degrees, 20 degrees, 30 degrees, 40 degrees, 50 degrees, 60 degrees, and 70 degrees at frequencies F 1 ~F 2０ in turn to determine their validity;

[0064] Fifth step, move the three arc-shaped brackets to the second azimuth angle n angle-1 , and then repeat the second to fourth steps in (3);

[0065] Sixth step, repeat the fifth step, and move the three arc-shaped brackets to n angle-2、 n angle-3 …n angle-m ; finally, obtain the validity information of the three measurement points on the paths with frequencies F 1 ~F 2０ , azimuth angles n angle-1、 n angle-2 …n angle-m and included angles of 0 degrees, 10 degrees, 20 degrees, 30 degrees, 40 degrees, 50 degrees, 60 degrees, and 70 degrees.

[0066] (5) Effective judgment of noise measurement points

[0067] Based on obtaining the effective information of the three measurement points on the paths of F 1 ~F 2０ frequencies and n angle-1、 n angle-2 …n angle-m azimuth angles, and the included angles of 0°, 10°, 20°, 30°, 40°, 50°, 60°, and 70°, it is necessary to comprehensively judge the effectiveness of the three measurement points on different azimuths and at each included angle path, so as to select the azimuth and included angle that are overall available and effective (that is, the measurement points on its path are effective noise measurement points). Taking the azimuth angle and the 0° included angle as an example of n angle-1 azimuth angle and the 0° included angle, judge its overall effectiveness in the following situations:

[0068] Situation 1: As long as all three measurement points are effective at each frequency from F 1 ~F 1０ then the three measurement points are overall effective, that is, the azimuth and included angle are effective (that is, the measurement points on its path are effective noise measurement points).

[0069] Situation 2: If all three measurement points are effective at each frequency from F 1 ~F 5 and at least 4 frequencies are effective among F 6 ~F 10 and at most 2 frequencies are invalid at each frequency from F 10 ~F 20 then the three measurement points are overall effective, that is, the azimuth and included angle are effective (that is, the measurement points on its path are effective noise measurement points);

[0070] Situation 3: If all three measurement points are effective at each frequency from F 1 ~F 5 and at least 3 frequencies are effective among F 6 ~F 10 and all three measurement points are effective at each frequency from F 10 ~F 20 then the three measurement points are overall effective, that is, the azimuth and included angle are effective (that is, the measurement points on its path are effective noise measurement points).

[0071] This method adopts the above implementation manner, calculates the reference distance for placing the arc-shaped bracket based on the rotor passing frequency and the sound speed, places the arc-shaped brackets at multiple different reference distances in the same azimuth angle, respectively emits sound from a horn and collects noise at the measurement points on the paths with the same azimuth and the same included angle at 1 to 20 times the reference frequency, analyzes the sound attenuation characteristics of the total sound pressure level on the paths with the same azimuth and the same included angle, and gives the judgment result of whether the noise measurement points are valid, thereby ensuring the effectiveness of the rotor rotation noise test data in the complex sound field environment during hovering.

[0072] As described above, the above are only specific embodiments of the present invention. The present invention is described in detail, and the unelaborated parts are conventional technologies. However, the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. The protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for judging the effectiveness of measuring points of the hovering model rotor noise, characterized in that, the effectiveness judgment method includes the following steps: Step S1: Calculate the reference distance for placing the arc-shaped bracket according to the rotor passing frequency and the speed of sound; Step S2: Place arc-shaped brackets at multiple different reference distances at the same azimuth angle; Step S3: For the measuring points on the same azimuth and the same included angle path, respectively perform horn sound emission and noise collection at 1 to 20 times the reference frequency; Step S4: According to the acquisition results, conduct an analysis of the sound attenuation characteristics of the total sound pressure level on the same azimuth and the same included angle path, and give a judgment result on whether the noise measuring point is effective; In Step S4, the analysis of the sound attenuation characteristics of the total sound pressure level on the same azimuth and the same included angle path includes the following steps: The first step is to use the background noise data to eliminate invalid measuring points and paths; The second step is to analyze the sound attenuation characteristics on the same azimuth and the same included angle path; The third step is to refer to the second step, and respectively and sequentially judge the one-third octave total sound pressure levels of the three measuring points on the 0-degree azimuth and 0-degree included angle path at frequencies F2 to F20 to determine their effectiveness; Judge whether the absolute value of the difference between the overall sound pressure of the one-third octave of the background noise of each microphone and N E-0-0 is greater than 3 times the standard deviation D iff-0-0 , if so, the measurement point is regarded as invalid, and at the same time, the measurement points with the same included angle of the other 2 arc-shaped branches corresponding to this measurement point are also regarded as invalid; Step 4: Referring to Step 2 and Step 3, respectively and in sequence, judge the one-third octave band total sound pressure levels of three measurement points on the paths of the 0-degree azimuth angle of frequencies F 1 ~F 2０ and at the included angles of 10 degrees, 20 degrees, 30 degrees, 40 degrees, 50 degrees, 60 degrees, and 70 degrees to determine their effectiveness; Step 5: Move the three arc-shaped brackets to the second azimuth angle n angle-1 , and then repeat the horn sound emission and noise collection; Step 6: Repeat Step 5 to successively move the three arc-shaped brackets to n angle-2、 n angle-3 …n angle-m ; finally obtain F 1 ~F 2０ frequency and n angle-1、 n angle-2 …n angle-m azimuth and the validity information of three measurement points on the paths with included angles of 0°, 10°, 20°, 30°, 40°, 50°, and 60°.

2. A method for judging the effectiveness of measuring points of the hovering model rotor noise according to claim 1, characterized in that, In Step S1, the calculation process of the reference distance for placing the arc-shaped bracket is: calculate the rotor passing frequency according to the actual working frequency of the rotor and the actual number of installed blade; combine the speed of sound and a certain integer multiple frequency to calculate the reference distance of the measuring point.

3. A method for judging the effectiveness of measuring points of the hovering model rotor noise according to claim 2, characterized in that, The calculation of the reference distance for the arc bracket placement includes: First step, according to the rotor operating frequency n specified in the test mission statement rpm and the actual number of installed blade numbers n rotor , the rotor passing frequency F is calculated according to the following formula 1 =n rpm ×n rotor ÷60; Step 2: Calculate F 2 and F 3 … F n for frequency multiplication. F n = n × n rpm × n rotor ÷ 60, where the subscript n of F n is an integer from 2 to 20; Step 3: Calculate the reference distance D of the measurement point, where D = 340 ÷ F 1 .

4. A method for judging the effectiveness of measuring points of the hovering model rotor noise according to claim 1, characterized in that, In Step S2, when placing the arc-shaped bracket, first determine the propeller disk plane and divide the azimuth angle to find the first azimuth angle of the propeller disk plane; then, with the hub center as the origin, extend along this azimuth angle to find a certain distance position point from the center point and sequentially place multiple arc-shaped brackets; and evenly install multiple microphones along the arc-shaped rod of each bracket in sequence, and make corresponding markings for each microphone.

5. A method for judging the effectiveness of measuring points of the hovering model rotor noise according to claim 1, characterized in that, In Step S3, the horn sound emission and noise collection are carried out in the following manner; The first step is to hang the standard sound source at a certain height directly above the hub center, and the sound source is facing the arc-shaped bracket; The second step is to power on and preheat the noise measurement system; The third step is to start the software of the noise collection system, set the sampling frequency, and simultaneously collect the sound pressure data and background noise; The fourth step is to calculate the one-third octave total sound pressure level of the background noise of each microphone; The fifth step is to turn on the sound source, emit a single-frequency sound corresponding to the first integer multiple frequency, start the software of the noise collection system, and set the same sampling frequency as in the third step; The sixth step is to calculate the one-third octave total sound pressure level of each microphone at this frequency; Step 7: Repeat Step 5 to let the sound source emit the single-frequency sound corresponding to the second integral multiple frequency, then collect the sound at this frequency, and then repeat Step 6 to calculate the overall sound pressure level of each microphone at one-third octave band at this frequency; Step 8: Repeat Step 7 to let the sound source sequentially emit the single-frequency sounds corresponding to the Nth integral multiple frequency, and collect and calculate the overall sound pressure level of each microphone at one-third octave band at each frequency.

6. A method for judging the effectiveness of noise measurement points of a hovering model rotor as described in claim 1, characterized in that, the specific judgment process for judging the effectiveness of noise measurement points includes the following steps: After obtaining F 1 ~F 2０ frequency and n angle-1、 n angle-2 …n angle-m On the basis of the azimuth angles and the validity information of the three measurement points on the paths with included angles of 0 degrees, 10 degrees, 20 degrees, 30 degrees, 40 degrees, 50 degrees, and 60 degrees, the validity of the three measurement points on the paths with different azimuths and each included angle is comprehensively judged to select the azimuth and included angle that are overall available and effective.

7. A method for judging the effectiveness of noise measurement points of a hovering model rotor as described in claim 6, characterized in that, the judgment of the effectiveness of noise measurement points includes the following three situations: If F 1 ~F 1０ If all three measurement points are valid at each frequency, then overall these three measurement points are valid, that is, this azimuth and included angle are valid; If F 1 ~F 5 all three measurement points are valid at each frequency, and at least 4 frequencies are valid in F 6 ~F 10 and at most 2 frequencies are invalid at each frequency in F 10 ~F 20 then overall these three measurement points are valid, that is, this azimuth and included angle are valid; If F 1 ~F 5 all three measurement points are valid at each frequency, and for F 6 ~F 10 at least 3 frequencies are valid, for F 10 ~F 20 all three measurement points are valid at each frequency, then overall these three measurement points are valid, that is, this azimuth and included angle are valid.

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