CN108051659B - Method for separating and extracting rotor noise - Google Patents
Method for separating and extracting rotor noise Download PDFInfo
- Publication number
- CN108051659B CN108051659B CN201711251502.1A CN201711251502A CN108051659B CN 108051659 B CN108051659 B CN 108051659B CN 201711251502 A CN201711251502 A CN 201711251502A CN 108051659 B CN108051659 B CN 108051659B
- Authority
- CN
- China
- Prior art keywords
- noise
- rotor
- frequency
- domain signal
- helicopter
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
- G01R29/26—Measuring noise figure; Measuring signal-to-noise ratio
Abstract
The invention discloses a method for separating and extracting rotor noise, and belongs to the technical field of helicopter noise tests. The method is suitable for separating and extracting the helicopter rotor noise, and comprises the following steps: the method comprises the following steps of firstly, obtaining a rotor noise fundamental frequency, an engine noise fundamental frequency and a tail rotor noise fundamental frequency of a helicopter; secondly, carrying out Fourier transform on the measured sound pressure time domain signal of the helicopter noise to convert the sound pressure time domain signal into a frequency domain signal; selecting cut-off frequency to carry out high-pass filtering and amplitude attenuation of the selected frequency band, and eliminating the influence of environmental noise, engine noise and tail rotor noise from the frequency domain signal; and fourthly, performing inverse Fourier transform on the processed frequency domain signal, thereby extracting a sound pressure time domain signal of the rotor noise. The invention attenuates and rejects environmental noise, tail rotor noise and engine noise in the frequency domain signal, can obviously see the periodic characteristic of the rotor noise signal in the time domain signal, and can simply and quickly extract and separate the rotor noise.
Description
Technical Field
The invention belongs to the technical field of helicopter noise tests, and particularly relates to a method for separating and extracting rotor noise.
Background
Rotor noise is the main source of helicopter far field noise, researches rotor noise characteristic, and then carries out the rotor and falls the design of making an uproar, can increase substantially the helicopter and synthesize stealthy characteristic. To this end, a large number of helicopter noise measurement tests have been carried out at home and abroad. However, the research on the helicopter noise is recorded in the literature, and the research on the rotor noise extraction from the helicopter noise is not found. The helicopter noise comprises noise signals such as rotor noise, environmental noise, engine noise, tail rotor noise and the like, so that the research on how to extract the rotor noise signals from the helicopter noise data has certain significance.
Disclosure of Invention
The purpose of the invention is as follows: in order to solve the problems, the invention provides a method for separating and extracting rotor noise, which comprises the steps of carrying out Fourier transform on a sound pressure time domain signal of helicopter noise obtained through measurement to convert the sound pressure time domain signal into a frequency domain signal, removing the influences of environmental noise, engine noise and tail rotor noise from the frequency domain signal through high-pass filtering and amplitude attenuation of a selected frequency band, and carrying out inverse Fourier transform on the processed frequency domain signal so as to extract and obtain a time domain signal and a frequency domain signal of the rotor noise.
The technical scheme of the invention is as follows: a method for separating and extracting rotor noise is suitable for separating and extracting the rotor noise of a helicopter, and comprises the following steps:
the method comprises the following steps of firstly, obtaining a rotor noise fundamental frequency, an engine noise fundamental frequency and a tail rotor noise fundamental frequency of a helicopter;
secondly, carrying out Fourier transform on the measured sound pressure time domain signal of the helicopter noise to convert the sound pressure time domain signal into a frequency domain signal;
selecting cut-off frequency to carry out high-pass filtering and amplitude attenuation of the selected frequency band, and eliminating the influence of environmental noise, engine noise and tail rotor noise from the frequency domain signal;
and fourthly, performing inverse Fourier transform on the processed frequency domain signal, thereby extracting a sound pressure time domain signal of the rotor noise.
Preferably, the selected frequency band amplitude is capable of attenuating engine and tail rotor noise while not corrupting the noise signal at the fundamental frequencies of the rotor orders.
Preferably, the selected cut-off frequency should combine the environmental noise characteristic and the rotor noise fundamental frequency, so as to attenuate the environmental noise without damaging the rotor noise signal.
Preferably, the amplitudes of frequency bands near frequency points which are integral multiples of the engine noise fundamental frequency and the tail rotor noise fundamental frequency in the high-pass filtered helicopter noise frequency domain signal are attenuated.
The technical scheme of the invention has the beneficial technical effects that: according to the method for separating and extracting the rotor noise, the time domain signal and the frequency domain signal of the rotor noise are extracted after processing, the environmental noise, the tail rotor noise and the engine noise are attenuated and removed in the frequency domain signal, the periodic characteristic of the rotor noise signal can be obviously seen in the time domain signal, and the rotor noise can be simply and quickly extracted and separated.
Drawings
FIG. 1 is a frequency domain signal diagram of the sound pressure level of the environmental noise according to a preferred embodiment of the method for separating and extracting the rotor noise of the present invention;
FIG. 2 is a sound pressure time domain signal diagram of helicopter noise according to a preferred embodiment of the method for separately extracting rotor noise of the present invention;
FIG. 3 is a graph of frequency domain signals of sound pressure levels of helicopter noise in accordance with a preferred embodiment of the method of the present invention for isolating and extracting rotor noise;
FIG. 4 is a diagram of a helicopter rotor noise sound pressure time domain signal obtained by separation and extraction according to a preferred embodiment of the method for separating and extracting rotor noise of the present invention;
fig. 5 is a diagram of a sound pressure level frequency domain signal of helicopter rotor noise obtained by separation and extraction according to a preferred embodiment of the method for separating and extracting rotor noise of the present invention.
Detailed Description
In order to make the implementation objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be described in more detail below with reference to the accompanying drawings in the embodiments of the present invention. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are only some, but not all embodiments of the invention. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
The helicopter noise includes environmental noise, engine noise, tail rotor noise and rotor noise, the energy of the environmental noise is concentrated on a low-frequency part, and the engine noise, the tail rotor noise and the rotor noise are concentrated on harmonic waves under a certain fundamental frequency.
Aiming at the characteristics of all components of helicopter noise, the invention provides a method for separating and extracting rotor noise from the helicopter noise, which comprises the following specific implementation steps of:
1) acquiring a rotor noise fundamental frequency, an engine noise fundamental frequency and a tail rotor noise fundamental frequency of a helicopter;
2) carrying out Fourier transform on the sound pressure time domain signal of the helicopter noise obtained by measurement to convert the sound pressure time domain signal into a frequency domain signal;
3) selecting cut-off frequency to carry out high-pass filtering and amplitude attenuation of a selected frequency band, and eliminating the influence of environmental noise, engine noise and tail rotor noise from a frequency domain signal;
4) and performing inverse Fourier transform on the processed frequency domain signal, thereby extracting a sound pressure time domain signal of the rotor noise.
In the embodiment, the proper cut-off frequency is selected to carry out high-pass filtering on the helicopter noise frequency domain signal, so that the influence of the environmental noise signal is attenuated; the cut-off frequency is selected according to the environmental noise characteristic and the rotor noise fundamental frequency, and the environmental noise is attenuated while the rotor noise signal is not damaged.
In the embodiment, the amplitudes of frequency bands near integral multiple frequency points of the engine noise fundamental frequency and the tail rotor noise fundamental frequency in the high-pass filtered helicopter noise frequency domain signal are attenuated;
the selection of the amplitude of the frequency section needs to ensure that noise signals under each order of fundamental frequency of the rotor wing are not damaged while noise of an engine and a tail rotor is attenuated.
In the embodiment, the total sound pressure level of the noise of the rotor wing is obtained by superposing the sound pressure levels of all frequencies in the processed noise frequency domain signal;
and performing inverse Fourier transform on the processed frequency spectrum (frequency domain signal) to obtain a rotor wing noise time domain signal.
The method is based on the existing mature technology and method, is simple and rapid, has strong practicability, and has certain application value for the design and development of advanced low-noise rotors of helicopters.
Fig. 1 to 5 show an application example of the method for separating and extracting rotor noise from noise signals of an unmanned helicopter.
In this example, the fundamental frequency of rotor noise is 28.47Hz, the fundamental frequency of engine noise is 203.2Hz, and the fundamental frequency of tail rotor noise is 164.8 Hz.
The total sound pressure level of the helicopter noise before the helicopter noise is processed by the method is 92.97dB, and the total sound pressure level of the rotor noise extracted after the helicopter noise is processed is 86.55 dB.
Fig. 1 is a frequency spectrum distribution diagram of environmental noise, the environmental noise is mainly concentrated in a low-frequency part, and the distribution characteristic of the environmental noise and the magnitude of the fundamental frequency of the rotor noise are combined, in this example, the high-pass filtering cut-off frequency is selected to be 20 Hz; FIGS. 2 and 3 are time and frequency domain signals of the helicopter noise before processing, from which it can be seen that the engine noise signal occupies a major part of the noise signal, and the periodic characteristics of the rotor noise signal are difficult to find in the time domain signal; fig. 4 and 5 show time domain and frequency domain signals of the rotor noise extracted after the processing by the method, in which the environmental noise, the tail rotor noise and the engine noise are attenuated and removed in the frequency domain signals, and the periodic characteristics of the rotor noise signals can be clearly seen in the time domain signals.
According to the method, the sound pressure time domain signal of the helicopter noise obtained through measurement is subjected to Fourier transform and converted into a frequency domain signal, the influence of environmental noise, engine noise and tail rotor noise is eliminated from the frequency domain signal through high-pass filtering and amplitude attenuation of a selected frequency band, and the processed frequency domain signal is subjected to inverse Fourier transform, so that the time domain signal and the frequency domain signal of the rotor noise are extracted and obtained.
Finally, it should be pointed out that: the above examples are only for illustrating the technical solutions of the present invention, and are not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (4)
1. A method for separating and extracting rotor noise is suitable for separating and extracting the rotor noise of a helicopter, and is characterized by comprising the following steps:
the method comprises the following steps of firstly, obtaining a rotor noise fundamental frequency, an engine noise fundamental frequency and a tail rotor noise fundamental frequency of a helicopter;
secondly, carrying out Fourier transform on the measured sound pressure time domain signal of the helicopter noise to convert the sound pressure time domain signal into a frequency domain signal;
selecting cut-off frequency to carry out high-pass filtering and amplitude attenuation of the selected frequency band, and eliminating the influence of environmental noise, engine noise and tail rotor noise from the frequency domain signal;
and fourthly, performing inverse Fourier transform on the processed frequency domain signal, thereby extracting a sound pressure time domain signal of the rotor noise.
2. The method of separating and extracting rotor noise according to claim 1, wherein: the selected frequency band amplitude is capable of attenuating engine and tail rotor noise while not corrupting the noise signal at the fundamental frequency of each order of the rotor.
3. The method of separating and extracting rotor noise according to claim 1, wherein: the selected cut-off frequency should be combined with the environmental noise characteristic and the rotor noise fundamental frequency, so that the environmental noise is attenuated and the rotor noise signal is not damaged.
4. The method of separating and extracting rotor noise according to claim 1, wherein: and attenuating the amplitudes of frequency bands near frequency points of integral multiples of the engine noise fundamental frequency and the tail rotor noise fundamental frequency in the high-pass filtered helicopter noise frequency domain signal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201711251502.1A CN108051659B (en) | 2017-12-01 | 2017-12-01 | Method for separating and extracting rotor noise |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201711251502.1A CN108051659B (en) | 2017-12-01 | 2017-12-01 | Method for separating and extracting rotor noise |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN108051659A CN108051659A (en) | 2018-05-18 |
| CN108051659B true CN108051659B (en) | 2020-05-12 |
Family
ID=62121914
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201711251502.1A Active CN108051659B (en) | 2017-12-01 | 2017-12-01 | Method for separating and extracting rotor noise |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN108051659B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112816937B (en) * | 2020-12-23 | 2022-10-28 | 中国船舶重工集团有限公司第七一0研究所 | Helicopter scale estimation method and device based on fundamental frequency spectrum azimuth angle change rate |
| CN113654652B (en) * | 2021-09-17 | 2024-03-19 | 广东电网有限责任公司 | Fault identification method of direct current control protection device and related device |
| CN114492095B (en) * | 2022-04-18 | 2022-11-29 | 北京蓝天航空科技股份有限公司 | Jet engine noise simulation method and system based on spectrum analysis |
| CN115186221B (en) * | 2022-08-05 | 2024-01-12 | 南京航空航天大学 | Rotor blade-vortex interference noise extraction method and system |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103530482A (en) * | 2013-11-04 | 2014-01-22 | 东南大学 | Method for forecasting noise value of propeller in uneven inflow |
| CN104034970A (en) * | 2014-05-22 | 2014-09-10 | 浙江大学 | Sound level measurement method based on computer sound card |
| CN105203999A (en) * | 2015-10-20 | 2015-12-30 | 陈昊 | Rotorcraft early-warning device and method |
| CN105486938A (en) * | 2014-09-19 | 2016-04-13 | 国家电网公司 | Transformer station mixed noise separation method |
| CN106777542A (en) * | 2016-11-23 | 2017-05-31 | 大连理工大学 | Spring leaf propeller flow noise prediction method |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7900869B2 (en) * | 2004-05-06 | 2011-03-08 | Zf Friedrichshafen Ag | Helicopter rotor control system with individual blade control |
-
2017
- 2017-12-01 CN CN201711251502.1A patent/CN108051659B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103530482A (en) * | 2013-11-04 | 2014-01-22 | 东南大学 | Method for forecasting noise value of propeller in uneven inflow |
| CN104034970A (en) * | 2014-05-22 | 2014-09-10 | 浙江大学 | Sound level measurement method based on computer sound card |
| CN105486938A (en) * | 2014-09-19 | 2016-04-13 | 国家电网公司 | Transformer station mixed noise separation method |
| CN105203999A (en) * | 2015-10-20 | 2015-12-30 | 陈昊 | Rotorcraft early-warning device and method |
| CN106777542A (en) * | 2016-11-23 | 2017-05-31 | 大连理工大学 | Spring leaf propeller flow noise prediction method |
Non-Patent Citations (1)
| Title |
|---|
| 直升机噪声理论分析;祝龙石;《制导与引信》;19941230(第4期);第10-15页 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN108051659A (en) | 2018-05-18 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN108051659B (en) | Method for separating and extracting rotor noise | |
| CN108801634B (en) | The method and its application of bearing fault characteristics frequency are extracted based on singular value decomposition and the frequency band entropy of optimization | |
| BR112013020482A2 (en) | apparatus and method for processing a decoded audio signal in a spectral domain | |
| CN109001703A (en) | A kind of sea clutter denoising method based on the processing of wavelet packet multi-threshold | |
| CN111769810B (en) | Fluid mechanical modulation frequency extraction method based on energy kurtosis spectrum | |
| CN105356886B (en) | Power line noise compression method and device based on compressed sensing | |
| CN109932624B (en) | Cable partial discharge period narrow-band interference denoising method based on Gaussian scale space | |
| CN102624349B (en) | Harmonic noise and white-noise interference eliminating method with low distortion to initial data | |
| CN102176312B (en) | System and method for reducing burst noise through wavelet trapped wave | |
| CN104581519A (en) | Noise reduction earphone and noise reduction method thereof | |
| CN106094046A (en) | Time domain aviation electromagnetic data de-noising method based on singular value decomposition and wavelet analysis | |
| CN105785346B (en) | A kind of unknown object line-spectrum detection method and system based on phase variance weighting | |
| CN107991531A (en) | Power grid harmonic wave detection method based on variation mode decomposition and removal noise | |
| KR101303192B1 (en) | Passive sonar system and demon treatment improving method | |
| CN109712639A (en) | A kind of audio collecting system and method based on wavelet filter | |
| CN115235610A (en) | Method for extracting modulation frequency of boost pump based on weighted enhancement envelope spectrum | |
| Zaitsev | Elimination on power line interference from ECG signal using combined bidirectional narrow-band notch filter | |
| CN104037770B (en) | A kind of adaptive filter method of electric harmonic | |
| CN114858430A (en) | Mechanical seal acoustic emission signal noise reduction method based on LCD-wavelet new threshold | |
| KR101323592B1 (en) | Method for enhancing demon processing performance using multiband processing | |
| CN109632945A (en) | A kind of noise-reduction method suitable for Pulsed eddy current testing signal | |
| CN105662336A (en) | Signal de-noising processing method and apparatus | |
| CN106629929B (en) | Energy-concerving and environment-protective sewage equipment | |
| CN116304584B (en) | Self-adaptive noise filtering method based on envelope spectrum peak value screening | |
| CN203849342U (en) | Transformer sound anomaly monitoring device |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |