Airplane ground acoustic characteristic field measurement method

Abstract

The invention provides an aircraft ground acoustic characteristic field measurement method, and belongs to the technical field of aircraft noise control, and the method comprises the steps: determining an aircraft test piece type used for ground acoustic characteristic measurement, the aircraft test piece type being a full-size aircraft or an aircraft cabin; aircraft acoustic characteristic measurement is carried out on the test piece, and the aircraft acoustic characteristic measurement comprises static sound insulation characteristic measurement, cabin reverberation time measurement, engine or power device driving measurement, airborne equipment noise measurement and sound vibration correlation measurement; and obtaining the static sound insulation characteristic of the airframe structure, the reverberation time of a cabin, the surface noise characteristic of the aircraft, the engine noise directivity, the engine noise source characteristic, the attenuation characteristic of the noise radiation value of airborne equipment along with the distance in different directions and the coupling characteristic of noise and vibration according to the measurement result of the acoustic characteristic of the aircraft. According to the method, the acoustic characteristics of the actual installation state of the airborne equipment are measured by using the full-size aircraft or the aircraft cabin, and the effectiveness of aircraft noise control measures can be verified.

Description

Technical Field

[0001] This application belongs to the field of aircraft noise control technology, and specifically relates to a method for on-site measurement of the ground acoustic characteristics of an aircraft. Background Technology

[0002] The environmental impact of aircraft noise is receiving increasing attention, encompassing two aspects: the impact of aircraft noise on the cabin environment, which directly affects passengers' experience of flight comfort and determines the aircraft's market competitiveness; and the impact of aircraft noise on the external environment, which relates to the aircraft's environmental performance and is subject to the international standard Annex 16 "Environmental Protection" Volume 1 Aircraft Noise of the Convention on International Civil Aviation and the domestic "Regulations on Noise for Aircraft Type and Airworthiness Certification".

[0003] To validate aircraft noise control designs, aircraft noise measurements are necessary. Current aircraft noise measurement methods are limited to laboratory measurements and only apply to panel-level airframe components; ground noise measurement methods are lacking for full-size aircraft or cabin sections. Summary of the Invention

[0004] The purpose of this application is to provide a method for on-site measurement of the ground acoustic characteristics of an aircraft, in order to solve or mitigate at least one of the problems in the prior art.

[0005] The technical solution of this application is: a method for on-site measurement of the ground acoustic characteristics of an aircraft, comprising:

[0006] Determine the type of aircraft test piece used for ground acoustic characteristic measurements, wherein the aircraft test piece type is a full-size aircraft or an aircraft section;

[0007] The test specimen is subjected to aircraft acoustic characteristic measurements, including static sound insulation characteristic measurements, cabin reverberation time measurements, engine or power plant start-up measurements, airborne equipment noise measurements, and sound-vibration correlation measurements. Based on the aircraft acoustic characteristic measurement results, the static sound insulation characteristics of the airframe structure, cabin reverberation time, aircraft surface noise characteristics, engine noise directivity and engine noise source characteristics, attenuation characteristics of airborne equipment noise radiation values ​​in different directions with distance, and noise-vibration coupling characteristics are obtained.

[0008] In at least one embodiment of this application, the process of measuring the static sound insulation characteristics of the test specimen includes:

[0009] To fix a full-size aircraft or cabin section in place, keeping it stationary.

[0010] Microphones are arranged inside and outside the test specimen to capture sound signals, wherein the microphones inside and outside the test specimen are arranged at the same height and at a predetermined distance from the structural surface of the test specimen.

[0011] Under noise measurement conditions where all engines and onboard equipment are not operating, and there are no noise sources or meteorological conditions affecting the acoustic measurements, the background noise inside and outside the test specimen is measured simultaneously to obtain the sound pressure level inside the test specimen. and external sound pressure level ;

[0012] Loudspeakers are placed outside or inside the test specimen to serve as noise sources for excitation, while the sound pressure level inside the test specimen is measured. and external sound pressure level This allows for the acquisition of noise signals from both the inside and outside of the test specimen.

[0013] Determine whether the background noise measurement is valid;

[0014] When the background noise measurement is valid, the static sound insulation characteristics of the body structure can be calculated.

[0015] Preferably, the method for determining whether the background noise measurement is effective is as follows: the sound pressure level of the background noise in the environment should be at least 10 dB lower than the sound pressure level during the acoustic measurement process.

[0016] Preferably, the static sound insulation characteristic L of the body structure G for:

[0017] When the loudspeaker is placed outside the test specimen, ;

[0018] When the loudspeaker is placed inside the test specimen .

[0019] In at least one embodiment of this application, the process of measuring the reverberation time of the test specimen includes:

[0020] To fix a full-size aircraft or cabin section in place, keeping it stationary.

[0021] Multiple microphones are arranged inside the test piece to capture sound signals;

[0022] Under noise measurement conditions where all engines and airborne equipment are not operating, and there are no noise sources or meteorological conditions affecting the acoustic measurements, the background noise inside the test specimen is measured to obtain the sound pressure level inside the test specimen. ;

[0023] Noise excitation was performed inside the test specimen, and the noise signal at each noise point inside the test specimen was measured simultaneously.

[0024] Determine whether this background noise measurement is valid;

[0025] When the background noise measurement is valid, continuously record the noise value of the excitation noise and plot the noise attenuation curve. Determine the reverberation time based on the noise attenuation curve.

[0026] Preferably, the multiple microphones are arranged at staggered heights.

[0027] Preferably, the method for noise excitation inside the test piece includes: interrupting the sound source method, that is, quickly cutting off the sound source after the sound reaches a steady state; or using the pulse sound source method, that is, using blasting sound as the sound source; or the sinusoidal frequency sweep method, that is, the sound source continuously sweeps the frequency signal, and the frequency band attenuation characteristics are analyzed by Fourier transform.

[0028] Preferably, the method for determining the reverberation time is as follows:

[0029] The reverberation time is the time required for the average sound energy density to decay from its original value to 60 dB by continuously measuring the decay curve of the excitation noise using a microphone. Alternatively, use an initial sound pressure level attenuation L. a To L b Extrapolate the time required for 60dB decay to the given conditions.

[0030] In at least one embodiment of this application, the process of measuring the engine or power unit running noise of the test specimen includes:

[0031] To fix a full-size aircraft or cabin section in place, keeping it stationary.

[0032] Multiple microphones are arranged inside and outside the test piece, and microphones are also arranged on the surface of the test piece.

[0033] Under the condition of meeting noise measurement requirements, the background noise inside and outside the test piece is measured simultaneously to obtain the sound pressure level inside the test piece. and external sound pressure level ;

[0034] Using the noise of the engine or power unit during operation as the noise excitation source, the noise signals at various measurement points on the surface, inside and outside of the test piece are measured simultaneously to obtain the noise impact of the engine or power unit on the aircraft cabin, airframe structure and aircraft exterior.

[0035] To determine whether the noise measurements of the surface, interior, and exterior of the test piece were valid;

[0036] When the noise measurement is valid, the cabin noise characteristics, aircraft surface noise characteristics, engine noise directivity, and engine noise source characteristics when the engine or power unit is running can be obtained from the noise data.

[0037] Preferably, one or more microphones are arranged on the surface of the test piece in the area of ​​interest to measure the noise signal when the engine or power unit is running;

[0038] The microphones arranged inside the test piece are arranged in an array to locate and identify acoustically weak points or secondary noise sources inside the test piece.

[0039] Microphones arranged in an array outside the test piece are used to locate and identify engine noise sources and noise directivity.

[0040] Preferably, the condition for satisfying the noise measurement is:

[0041] The aircraft or cabin is placed in an open and flat environment, with no noise sources or meteorological conditions that could affect the acoustic measurements. There are no dense or tall grasses, shrubs, or trees or other materials with strong sound absorption properties nearby. There is no precipitation during the test and measurement process. The atmospheric temperature is between -10℃ and 35℃, the relative humidity is between 20% and 95%, and the average wind speed does not exceed 13km / h.

[0042] Preferably, the method for determining whether the noise measurements of the surface, interior, and exterior of the test piece are valid is as follows:

[0043] When the engine or power unit is operating, the noise level measured outside the aircraft is more than 10 dB higher than the background noise level outside the aircraft, and the noise level measured inside the aircraft is more than 10 dB higher than the background noise level inside the aircraft.

[0044] In at least one embodiment of this application, the process of measuring airborne equipment noise on the test specimen includes:

[0045] Fix the airborne equipment to ensure it is in a quiet environment;

[0046] Determine the noise measurement envelope of the airborne equipment, and arrange microphones on the envelope to form measurement points;

[0047] The background noise of the test environment is measured simultaneously under conditions where there are no noise or vibration sources in the surrounding environment that would affect the acoustic measurements, nor are there any meteorological conditions that would affect the acoustic measurements.

[0048] To enable the airborne equipment to operate, and simultaneously measure the noise signal at each measurement point;

[0049] Determine whether this background noise measurement is valid;

[0050] When the background noise measurement is valid, repeat the above steps to measure the noise signal at different envelope distances;

[0051] The noise radiation value of airborne equipment and the attenuation characteristics of airborne equipment noise radiation value with distance in different directions are determined based on the noise signal at different envelope distances.

[0052] Preferably, each face of the envelope is a plurality of regularly sized surface units, the maximum side length of the surface unit does not exceed 3d, and the microphone is arranged at the center and corner points of the surface unit;

[0053] The distance d between the surface of the envelope and the surface of the airborne equipment is set to 0.3m, 0.5m and 1.0m respectively.

[0054] Preferably, the noise radiation value L of the airborne equipment target The calculation method is as follows:

[0055]

[0056] In the formula, It is the noise sound pressure level measured at the i-th noise measurement point on the 0.3m envelope surface.

[0057] Preferably, the noise radiation value of the airborne equipment exhibits a decay characteristic L with distance. decay The calculation is based on noise measurements taken at different distances along the same direction, using the following method:

[0058]

[0059] In the formula: L q These are noise measurements in the same direction. A, B, and C are empirical constants that can be calculated based on the noise measurement results.

[0060] In at least one embodiment of this application, the process of performing acoustic-vibration correlation measurement on the test specimen is as follows:

[0061] To fix a full-size aircraft or cabin section in place, keeping it stationary.

[0062] A microphone is placed inside the test piece, and a vibration sensor is placed on the structural surface of the test piece.

[0063] Under the condition that there are no noise sources or vibration sources in the surrounding environment that would affect the acoustic and vibration measurements, measure the background noise inside the test piece;

[0064] When the engine or power unit is running, it creates a noise excitation source.

[0065] Simultaneously measure the noise signal L at various measurement points inside the aircraft. i (i=1,2,3…,m) and vibration signal V j (j=1,2,3…,n), where m and n are the number of measurement points;

[0066] Determine whether this background noise measurement is valid;

[0067] The correlation coefficients of each noise measurement point and vibration measurement point are calculated based on the synchronously measured noise and vibration signals, thereby determining the correlation between cabin noise and airframe structural vibration.

[0068] The acoustic-vibration correlation coefficient matrix is ​​obtained based on the correlation coefficient, the acoustic-vibration correlation is determined, and the coupling characteristics of noise and vibration are evaluated based on the acoustic-vibration correlation.

[0069] Preferably, the correlation coefficient is calculated as follows:

[0070]

[0071] In the formula: R ij It is the correlation coefficient between the i-th noise measurement point and the j-th vibration measurement point;

[0072] L i It is the signal at the i-th noise measurement point, i=1,2,3…,m;

[0073] V j It is the signal of the j-th vibration measurement point, j=1,2,3…,n;

[0074] T is the signal duration;

[0075] τ is the time delay.

[0076] Preferably, the method for calculating the acoustic-vibration correlation coefficient matrix R is as follows:

[0077]

[0078] In the formula, the larger the value of the correlation coefficient matrix R, the stronger the correlation between the two signals, that is, the stronger the coupling effect between the noise signal at point i and the vibration signal at point j.

[0079] The ground acoustic characteristics measurement method of this application utilizes a full-size aircraft or aircraft compartment to measure the acoustic characteristics of airborne equipment in its actual installed state. This method can verify the effectiveness of aircraft noise control measures, evaluate the indicators of aircraft noise reduction performance, and provide support for aircraft noise reduction improvement and optimization. Attached Figure Description

[0080] 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.

[0081] Figure 1This is a schematic diagram of the overall method for on-site measurement of the ground acoustic characteristics of an aircraft according to this application.

[0082] Figure 2 This is a schematic diagram of static sound insulation characteristic measurement according to an embodiment of this application.

[0083] Figure 3 This is a schematic diagram of cabin reverberation time measurement according to an embodiment of this application.

[0084] Figure 4 This is a schematic diagram of engine or power unit driving noise measurement according to an embodiment of this application.

[0085] Figure 5 This is a schematic diagram of airborne equipment noise measurement according to an embodiment of this application.

[0086] Figure 6 This is a schematic diagram of acoustic-vibration correlation measurement according to an embodiment of this application. Detailed Implementation

[0087] 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.

[0088] To verify the effectiveness of aircraft noise control measures, evaluate the indicators of aircraft noise reduction performance, and provide support for the improvement and optimization of aircraft noise reduction, this application provides a method for on-site measurement of aircraft ground acoustic characteristics.

[0089] like Figure 1 As shown, the on-site measurement method for aircraft ground acoustic characteristics provided in this application includes:

[0090] Step S1: Determine the type of aircraft test piece used for acoustic characteristic measurement, wherein the test piece type is a full-size aircraft or an aircraft section (hereinafter referred to as test piece).

[0091] In this application, the full-size aircraft or aircraft segment can be a full-size aircraft model or segment model manufactured to actual dimensions, or it can be a real aircraft actually in operation. This application utilizes a full-size aircraft or segment to measure the acoustic characteristics of the airframe structure and onboard equipment under actual installed conditions, allowing for a more realistic evaluation of aircraft noise levels.

[0092] Step S2 involves conducting aircraft acoustic characteristic measurements on the test specimen. These measurements include static sound insulation characteristic measurements, cabin reverberation time measurements, engine or power unit start-up measurements, airborne equipment noise measurements, and sound-vibration correlation measurements. Based on the aircraft acoustic characteristic measurement results, the static sound insulation characteristics of the airframe structure, cabin reverberation time, aircraft surface noise characteristics, engine noise directivity and engine noise source characteristics, attenuation characteristics of airborne equipment noise radiation values ​​in different directions with distance, and noise-vibration coupling characteristics are obtained.

[0093] like Figure 2 As shown, the process of measuring the static sound insulation characteristics of the test specimen in this application includes:

[0094] Step S11: Secure the full-size aircraft or cabin section to bring it to a standstill;

[0095] Step S12: Microphones 2 are arranged inside and outside the test piece 1 to capture sound signals. The microphones 2 inside and outside the test piece 1 are arranged at the same height and at a certain distance from the structural surface of the test piece. In this embodiment of the application, the distance is set to 150mm.

[0096] Step S13: Under noise measurement conditions where all engines and / or airborne equipment are not operating, and there are no noise sources in the surrounding environment that would affect the acoustic measurements, and no meteorological conditions that would affect the acoustic measurements, simultaneously measure the background noise inside and outside the test piece 1 to obtain the sound pressure level inside the test piece 1. and external sound pressure level ;

[0097] Step S14: Place a loudspeaker outside or inside the test piece 1 to serve as a noise source for excitation, and simultaneously measure the sound pressure level inside the test piece 1. and external sound pressure level This allows for the acquisition of noise signals from both the inside and outside of the test specimen.

[0098] Step S15: Determine the validity of the background noise measurement according to the following formula, wherein the sound pressure level of the ambient background noise should be at least 10 dB lower than the sound pressure level during the acoustic measurement process, i.e.:

[0099] ;

[0100] Step S16: When the background noise measurement is valid, calculate the static sound insulation characteristic L of the body structure according to the following formula. G :

[0101] When the loudspeaker is placed outside of test piece 1 ;

[0102] When the speaker is placed inside test piece 1 .

[0103] like Figure 3 As shown, the process of measuring the reverberation time of the test specimen in this application includes:

[0104] Step S21: Secure the full-size aircraft or cabin section to bring it to a standstill;

[0105] Step S22: Arrange multiple microphones 2 inside the test piece 1 to capture sound signals, wherein the multiple microphones 2 are arranged at staggered heights, for example, as described in this application. Figure 3 In this embodiment, three microphones 2 are arranged, and the three microphones 2 are not exactly the same height.

[0106] Step S23: Under noise measurement conditions where all engines and / or airborne equipment are not operating, and there are no noise sources in the surrounding environment that could affect the acoustic measurements, and no meteorological conditions that could affect the acoustic measurements, measure the background noise inside test piece 1 to obtain the sound pressure level inside the test piece. ;

[0107] Step S24: Noise excitation is performed inside the test piece 1, and the noise signal at each noise point inside the test piece 1 is measured simultaneously;

[0108] The methods for noise excitation include: interrupting the sound source, which means quickly cutting off the sound source after the sound reaches a steady state; or using the pulse sound source, which means using blasting sound as the sound source; or the sinusoidal frequency sweep method, which means continuously sweeping the frequency signal of the sound source and analyzing the frequency band attenuation characteristics through Fourier transform.

[0109] Step S25: Determine whether the background noise measurement is valid according to the following formula, wherein the sound pressure level of the ambient background noise should be at least 10 dB lower than the sound pressure level during the acoustic measurement process, i.e.:

[0110] ;

[0111] Step S26: When the background noise measurement is valid, continuously record the noise value of the excitation noise and plot the noise attenuation curve. Determine the reverberation time based on the noise attenuation curve. ;

[0112] Among them, the attenuation curve of the excitation noise was continuously measured using microphone 2, and the average sound energy density was measured to decrease from its original value to 10 times its original value. -6 The time required for 60 dB is called the reverberation time. Alternatively, use an initial sound pressure level attenuation L. a (dB) to L b Extrapolate the (dB) case to the time required for 60dB decay.

[0113] like Figure 4 As shown, the process of measuring engine or power unit start-up noise on the test piece in this application includes:

[0114] Step S31: Secure the full-size aircraft or cabin section to bring it to a standstill;

[0115] Step S32: Arrange multiple microphones 2 inside the test piece 1 to capture sound signals, and arrange microphones 2 on the surface of the test piece 1 and arrange an arc-shaped microphone array 3 or a linear microphone array 4 parallel to the test piece 1 around the outside of the test piece 1.

[0116] In a preferred embodiment of this application, one or more microphones 2 can be arranged on the area of ​​interest on the surface of the test piece 1 to measure the noise signal when the engine or power unit is running.

[0117] The microphones 2 inside the test piece 1 can be arranged in the form of a microphone array to locate and identify acoustically weak parts or secondary noise sources inside the test piece 1.

[0118] The external microphones 2 of the test piece 1 can also be arranged in an array to locate and identify engine noise sources and noise directivity.

[0119] Step S33: Under suitable noise measurement conditions (the aircraft or cabin section should be placed in an open and flat environment, with no noise sources or meteorological conditions affecting the acoustic measurement, no dense or tall grass, shrubs, or trees or other materials with strong sound absorption characteristics nearby, no precipitation during the test measurement process, atmospheric temperature between -10℃ and 35℃, relative humidity between 20% and 95%, and average wind speed not exceeding 13km / h), simultaneously measure the background noise inside and outside the test piece 1 to obtain the sound pressure level inside the test piece 1. and external sound pressure level ;

[0120] Step S34: Using the noise of the engine or power unit when it is running as the noise excitation source, simultaneously measure the noise signals at various measurement points on the surface, inside and outside of the test piece 1 to obtain the noise impact of the engine or power unit noise on the aircraft cabin, airframe structure and aircraft exterior.

[0121] Step S35: Determine whether the noise measurements of the surface, interior, and exterior of the test piece are valid;

[0122] The judgment method is as follows: under the operating conditions of the engine or power unit, the noise level measured outside the aircraft should be more than 10 dB higher than the background noise level outside the aircraft (i.e., in a stationary state), and the noise level measured inside the aircraft should be more than 10 dB higher than the background noise level inside the aircraft (i.e., in a stationary state).

[0123] Step S36: When the noise measurement is valid, obtain the cabin noise characteristics, aircraft surface noise characteristics, engine noise directivity, and engine noise source characteristics when the engine or power unit is running, based on the noise data.

[0124] like Figure 5 As shown, the process of measuring airborne equipment noise on the test specimen in this application includes:

[0125] Step S41: Secure the airborne equipment 5 to a quiet environment;

[0126] Step S42: Determine the noise measurement envelope 6 of the airborne equipment 5, and arrange the microphone 2 on the envelope 6 to form measurement points;

[0127] In this application, each face of the envelope is a plurality of regularly sized surface units, such as rectangular surface units, with the maximum side length of the surface unit not exceeding 3d. The microphone 2 is arranged at the center and corner points of the surface units. In addition, the distance between the surface of the envelope and the surface of the airborne equipment 5 is d, which is set to 0.3m, 0.5m and 1.0m respectively.

[0128] Step S43: Under conditions where there are no noise or vibration sources in the surrounding environment that would affect the acoustic measurements, and no meteorological conditions that would affect the acoustic measurements, simultaneously measure the background noise of the test environment;

[0129] Step S44: Run the airborne equipment 5 and simultaneously measure the noise signal at each measurement point;

[0130] Step S45: Determine whether the background noise measurement is valid. The judgment rule is: the sound pressure level of the background noise in the environment should be at least 10 dB lower than the sound pressure level during the acoustic measurement process.

[0131] Step S46: When the noise measurement is valid, repeat steps S42 to S45 to measure the noise signal at different envelope distances d.

[0132] Step S47: Determine the noise radiation value of the airborne equipment and the attenuation characteristics of the noise radiation value of the airborne equipment with distance in different directions based on the noise signal at different envelope distances d.

[0133] In this application, the airborne equipment noise radiation value L target The calculation method is as follows:

[0134]

[0135] In the formula, It is the noise sound pressure level measured at the i-th noise measurement point on the 0.3m envelope surface;

[0136] Attenuation characteristics of airborne equipment noise radiation value with distance L decay The calculation can be performed based on noise measurements taken at different distances along the same direction, as follows:

[0137]

[0138] In the formula: L q These are noise measurements in the same direction. A, B, and C are empirical constants that can be calculated based on the noise measurement results.

[0139] like Figure 6 As shown, the process of conducting acoustic-vibration correlation measurements on the test specimen in this application is as follows:

[0140] Step S51: Secure the full-size aircraft or cabin section to bring it to a standstill;

[0141] Step S52: Arrange a microphone 2 inside the test piece 1 and arrange a vibration sensor 7 on the structural surface of the test piece 1;

[0142] Step S53: Under the condition that there are no noise sources or vibration sources in the surrounding environment that would affect the acoustic and vibration measurements, measure the background noise inside the test piece 1;

[0143] Step S54: The engine or power unit starts, creating a noise excitation source;

[0144] Step S55: Simultaneously measure the noise signal L at each measurement point inside the aircraft. i (i=1,2,3…,m) and vibration signal V j (j=1,2,3…,n), where m and n are the number of measurement points;

[0145] Step S56: Determine whether the background noise measurement is valid. During the test, the noise level measured inside the test piece should be at least 10 dB higher than the background noise level inside the test piece.

[0146] Step S57: Calculate the correlation coefficients of each noise measurement point and vibration measurement point based on the synchronously measured noise and vibration signals, thereby determining the correlation between cabin noise and airframe structural vibration.

[0147] In this application, the formula for calculating the correlation coefficient is as follows:

[0148]

[0149] In the formula: R ij It is the correlation coefficient between the i-th noise measurement point and the j-th vibration measurement point;

[0150] L i It is the signal at the i-th noise measurement point, i=1,2,3…,m;

[0151] V j It is the signal of the j-th vibration measurement point, j=1,2,3…,n;

[0152] T is the signal duration;

[0153] τ is the time delay.

[0154] The acoustic-vibration correlation coefficient matrix is ​​obtained based on the correlation coefficient, the acoustic-vibration correlation is determined, and the coupling characteristics of noise and vibration are evaluated based on the acoustic-vibration correlation.

[0155] The acoustic-vibration correlation coefficient matrix R is as follows:

[0156]

[0157] The larger the value of the correlation matrix R, the stronger the correlation between the two signals, that is, the stronger the coupling effect between the noise signal at point i and the vibration signal at point j.

[0158] The ground acoustic characteristics measurement method of this application utilizes a full-size aircraft or aircraft compartment to measure the acoustic characteristics of airborne equipment in its actual installed state. This method can verify the effectiveness of aircraft noise control measures, evaluate the indicators of aircraft noise reduction performance, and provide support for aircraft noise reduction improvement and optimization.

[0159] 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 on-site measurement of the ground acoustic characteristics of an aircraft, characterized in that, include: Determine the type of aircraft test piece used for ground acoustic characteristic measurements, wherein the aircraft test piece type is a full-size aircraft or an aircraft section; The test specimen is subjected to aircraft acoustic characteristic measurements, including static sound insulation characteristic measurements, cabin reverberation time measurements, engine or power plant start-up measurements, airborne equipment noise measurements, and sound-vibration correlation measurements. Based on the aircraft acoustic characteristic measurement results, the static sound insulation characteristics of the airframe structure, cabin reverberation time, aircraft surface noise characteristics, engine noise directivity and engine noise source characteristics, attenuation characteristics of airborne equipment noise radiation values ​​in different directions with distance, and noise-vibration coupling characteristics are obtained.

2. The method for on-site measurement of aircraft ground acoustic characteristics as described in claim 1, characterized in that, The process of measuring the static sound insulation characteristics of the test specimen includes: To fix a full-size aircraft or cabin section in place, keeping it stationary. Microphones are arranged inside and outside the test specimen to capture sound signals, wherein the microphones inside and outside the test specimen are arranged at the same height and at a predetermined distance from the structural surface of the test specimen. Under noise measurement conditions where all engines and onboard equipment are not operating, and there are no noise sources or meteorological conditions affecting the acoustic measurements, the background noise inside and outside the test specimen is measured simultaneously to obtain the sound pressure level inside the test specimen. and external sound pressure level ; Loudspeakers are placed outside or inside the test specimen to serve as noise sources for excitation, while the sound pressure level inside the test specimen is measured. and external sound pressure level This allows for the acquisition of noise signals from both the inside and outside of the test specimen. Determine whether the background noise measurement is valid; When the background noise measurement is valid, the static sound insulation characteristics of the body structure can be calculated.

3. The method for on-site measurement of aircraft ground acoustic characteristics as described in claim 2, characterized in that, The method to determine whether the background noise measurement is valid is as follows: the sound pressure level of the background noise in the environment should be at least 10 dB lower than the sound pressure level during the acoustic measurement process.

4. The method for on-site measurement of aircraft ground acoustic characteristics as described in claim 2, characterized in that, The static sound insulation characteristics L of the body structure G for: When the loudspeaker is placed outside the test specimen, ; When the loudspeaker is placed inside the test specimen .

5. The method for on-site measurement of aircraft ground acoustic characteristics as described in claim 1, characterized in that, The process of measuring the reverberation time of the test specimen includes: To fix a full-size aircraft or cabin section in place, keeping it stationary. Multiple microphones are arranged inside the test piece to capture sound signals; Under noise measurement conditions where all engines and airborne equipment are not operating, and there are no noise sources or meteorological conditions affecting the acoustic measurements, the background noise inside the test specimen is measured to obtain the sound pressure level inside the test specimen. ; Noise excitation was performed inside the test specimen, and the noise signal at each noise point inside the test specimen was measured simultaneously. Determine whether this background noise measurement is valid; When the background noise measurement is valid, continuously record the noise value of the excitation noise and plot the noise attenuation curve. Determine the reverberation time based on the noise attenuation curve.

6. The method for on-site measurement of aircraft ground acoustic characteristics as described in claim 5, characterized in that, The multiple microphones are arranged at staggered heights.

7. The method for on-site measurement of aircraft ground acoustic characteristics as described in claim 5, characterized in that, Methods for noise excitation inside the test piece include: interrupting the sound source method, which involves quickly cutting off the sound source after the sound reaches a steady state; or using the pulse sound source method, which uses blasting sound as the sound source; or the sinusoidal frequency sweep method, which involves continuously sweeping the frequency signal of the sound source and analyzing the frequency band attenuation characteristics through Fourier transform.

8. The method for on-site measurement of aircraft ground acoustic characteristics as described in claim 5, characterized in that, The method for determining reverberation time is as follows: The reverberation time is the time required for the average sound energy density to decay from its original value to 60 dB by continuously measuring the decay curve of the excitation noise using a microphone. Alternatively, use an initial sound pressure level attenuation L. a To L b Extrapolate the time required for 60dB decay to the given conditions.

9. The method for on-site measurement of aircraft ground acoustic characteristics as described in claim 1, characterized in that, The process of measuring engine or power unit operating noise on the test piece includes: To fix a full-size aircraft or cabin section in place, keeping it stationary. Multiple microphones are arranged inside and outside the test piece, and microphones are also arranged on the surface of the test piece. Under the condition of meeting noise measurement requirements, the background noise inside and outside the test piece is measured simultaneously to obtain the sound pressure level inside the test piece. and external sound pressure level ; Using the noise of the engine or power unit during operation as the noise excitation source, the noise signals at various measurement points on the surface, inside and outside of the test piece are measured simultaneously to obtain the noise impact of the engine or power unit on the aircraft cabin, airframe structure and aircraft exterior. To determine whether the noise measurements of the surface, interior, and exterior of the test piece were valid; When the noise measurement is valid, the cabin noise characteristics, aircraft surface noise characteristics, engine noise directivity, and engine noise source characteristics when the engine or power unit is running can be obtained from the noise data.

10. The method for on-site measurement of aircraft ground acoustic characteristics as described in claim 9, characterized in that, One or more microphones are placed on the surface of the test piece in the area of ​​interest to measure the noise signal of the engine or power unit when it is running. The microphones arranged inside the test piece are arranged in an array to locate and identify acoustically weak points or secondary noise sources inside the test piece. Microphones arranged in an array outside the test piece are used to locate and identify engine noise sources and noise directivity.

11. The method for on-site measurement of aircraft ground acoustic characteristics as described in claim 9, characterized in that, The conditions for satisfying noise measurement are as follows: The aircraft or cabin is placed in an open and flat environment, with no noise sources or meteorological conditions that could affect the acoustic measurements. There are no dense or tall grasses, shrubs, or trees or other materials with strong sound absorption properties nearby. There is no precipitation during the test and measurement process. The atmospheric temperature is between -10℃ and 35℃, the relative humidity is between 20% and 95%, and the average wind speed does not exceed 13km / h.

12. The method for on-site measurement of aircraft ground acoustic characteristics as described in claim 9, characterized in that, The method for determining the validity of the noise measurements on the surface, inside, and outside of the test piece is as follows: When the engine or power unit is operating, the noise level measured outside the aircraft is more than 10 dB higher than the background noise level outside the aircraft, and the noise level measured inside the aircraft is more than 10 dB higher than the background noise level inside the aircraft.

13. The method for on-site measurement of aircraft ground acoustic characteristics as described in claim 1, characterized in that, The process of measuring airborne equipment noise on the test specimen includes: Fix the airborne equipment to ensure it is in a quiet environment; Determine the noise measurement envelope of the airborne equipment, and arrange microphones on the envelope to form measurement points; The background noise of the test environment is measured simultaneously under conditions where there are no noise or vibration sources in the surrounding environment that would affect the acoustic measurements, nor are there any meteorological conditions that would affect the acoustic measurements. To enable the airborne equipment to operate, and simultaneously measure the noise signal at each measurement point; Determine whether this background noise measurement is valid; When the background noise measurement is valid, repeat the above steps to measure the noise signal at different envelope distances; The noise radiation value of airborne equipment and the attenuation characteristics of airborne equipment noise radiation value with distance in different directions are determined based on the noise signal at different envelope distances.

14. The method for on-site measurement of aircraft ground acoustic characteristics as described in claim 13, characterized in that, Each face of the envelope is a number of regularly sized surface units, the maximum side length of which does not exceed 3d, and the microphones are arranged at the center and corners of the surface units. The distance d between the surface of the envelope and the surface of the airborne equipment is set to 0.3m, 0.5m and 1.0m respectively.

15. The method for on-site measurement of aircraft ground acoustic characteristics as described in claim 13, characterized in that, The noise radiation value L of the airborne equipment target The calculation method is as follows: In the formula, It is the noise sound pressure level measured at the i-th noise measurement point on the 0.3m envelope surface.

16. The method for on-site measurement of aircraft ground acoustic characteristics as described in claim 15, characterized in that, The noise radiation value of the airborne equipment attenuates with distance L decay The calculation is based on noise measurements taken at different distances along the same direction, using the following method: In the formula: L q These are noise measurements in the same direction. A, B, and C are empirical constants that can be calculated based on the noise measurement results.

17. The method for on-site measurement of aircraft ground acoustic characteristics as described in claim 1, characterized in that, The process of performing acoustic-vibration correlation measurement on the test piece is as follows: To fix a full-size aircraft or cabin section in place, keeping it stationary. A microphone is placed inside the test piece, and a vibration sensor is placed on the structural surface of the test piece. Under the condition that there are no noise sources or vibration sources in the surrounding environment that would affect the acoustic and vibration measurements, measure the background noise inside the test piece; When the engine or power unit is running, it creates a noise excitation source. Simultaneously measure the noise signal L at various measurement points inside the aircraft. i (i=1,2,3…,m) and vibration signal V j (j=1,2,3…,n), where m and n are the number of measurement points; Determine whether this background noise measurement is valid; The correlation coefficients of each noise measurement point and vibration measurement point are calculated based on the synchronously measured noise and vibration signals, thereby determining the correlation between cabin noise and airframe structural vibration. The acoustic-vibration correlation coefficient matrix is ​​obtained based on the correlation coefficient, the acoustic-vibration correlation is determined, and the coupling characteristics of noise and vibration are evaluated based on the acoustic-vibration correlation.

18. The method for on-site measurement of aircraft ground acoustic characteristics as described in claim 17, characterized in that, The correlation coefficient is calculated as follows: In the formula: R ij It is the correlation coefficient between the i-th noise measurement point and the j-th vibration measurement point; L i It is the signal at the i-th noise measurement point, i=1,2,3…,m; V j It is the signal of the j-th vibration measurement point, j=1,2,3…,n; T is the signal duration; τ is the time delay.

19. The method for on-site measurement of aircraft ground acoustic characteristics as described in claim 18, characterized in that, The method for calculating the acoustic-vibration correlation coefficient matrix R is as follows: In the formula, the larger the value of the correlation coefficient matrix R, the stronger the correlation between the two signals, that is, the stronger the coupling effect between the noise signal at point i and the vibration signal at point j.

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