이동하는 소음원 위치 추정을 위한 다양한 빔형성 기법 적용

고영주(Yeong-Ju Go),이재형(Jaehyung Lee),최종수(Jong-Soo Choi),하재현(Jae-Hyoun Ha) 한국소음진동공학회 2016 한국소음진동공학회 논문집 Vol.26 No.5

Capabilities of several beamforming techniques are compared for estimating the position of a moving source. Beamforming has enabled to widen our perspective of aeroacoustics in wind tunnel experiments and has provided useful approach in array measurements. Meanwhile beamforming techniques have been developed in a way to improve estimation accuracy and to save ing effort at the same time. In order to achieve reasonable outcome from aeroacoustic measurement, it is important to identify the spectral characteristics of source and to select an appropriate beamformer. Though aeroacoustic sources normally generates broadband noises, many array signal processing have been focused on narrowband processing which makes calculation numerically efficient. However, calculation in frequency-domain requires selection of single frequency of interest which affects spatial resolution and sidelobe level as a consequence. To be able to localize broadband noise source, it is proposed to use broadband beamforming. The formulas implements the deletion of diagonal term from cross spectral matrix. In this study, trajectory of flying source emitting broadband noise was simulated and several beamformers are applied.

자유 음장 조건에서 빔형성 방법을 이용한 수직 및 경사입사 음향 임피던스의 측정

신창우(Chang Woo Shin),선종천(Jong Choen Sun),강연준(Yeon June Kang),백순권(Soon Kwon Paik) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

The improved Beamforming method is proposed to measure the acoustic impedance and absorption coefficient in a free field. It is possible to estimate the acoustic impedance by separating incident and reflected signals with the Adaptive Nulling Method. The wavelet shrinkage method is applied to reduce the White Gaussian noise. Transfer function vector is used for obtaining better results instead of pressure vector. The proposed method was verified by the comparison of measurement and theoretical method. The results show that the proposed method is efficient to measure acoustic impedance for frequencies higher than 400 ㎐.

빔형성방법을 이용한 회전하는 음원의 위치 판별에 관한 연구

이재형(Lee, Jaehyung),홍석호(Hong, Suk-Ho),최종수(Choi, Jong-Soo) 한국소음진동공학회 2004 한국소음진동공학회 논문집 Vol.14 No.12

The positions of rotating sound sources have been localized by experiments with the Doppler effects removed. In order to de-Dopplerize the sound signals emitted from moving sources, two kinds of signal reconstruction methods were applied. One is the forward propagation method and the other is the backward propagation method. Forward propagation method analyze the source emission time based on the instantaneous distance between sensors and the assumed source position, then the signals are reconstructed with respect to the emission time. On the other hand, the backward method uses time delay to do-Dopplerize the acquired data for the received time of reference. In both techniques. the reconstructed signal data were processed using beamforming algorithm to produce power distributions at the frequencies of interest. Experiments have been carried out for varying frequencies, rotating speeds and the object distances. It is shown that the forward propagation method gives better performance in locating source position than the backward propagation method.

빔형성 방법을 이용한 함정 추진기 소음 위치 추정에 대한 실험적 연구

황은수,정홍석,이석규,설한신 한국소음진동공학회 2022 한국소음진동공학회 논문집 Vol.32 No.4

In this study, an experimental investigation was conducted to estimate the location of propeller cavitation using a beamforming method with a hydrophone array. The sensors were mounted on the hull surface above the port side propeller and arranged in a single-armed spiral. To validate the performance of the sensor array, a test was performed using a reference source ITC-1032. The results showed that the location of the sound source was well predicted. A scaled model-ship test was conducted for various test conditions in the large cavitation tunnel of KRISO. Propeller cavitation was observed using a video camera with stroboscopes, and the propeller noise were measured by on-board sensors. From the observations and estimations, we concluded that the dominant cavitation was well estimated.

잡음 속에 묻힌 임펄스 소음원 위치 추정

김양한(Kim, Yang-Hann),최영철(Choi, Young-Chul) 한국소음진동공학회 2004 한국소음진동공학회 논문집 Vol.14 No.9

This paper addresses the way in which we can find where impulsive noise sources are. Specifically, we have an interest in the case that the signal is embedded in noise. We propose a signal processing method that can identify impulsive sources' location. The method is robust with respect to spatially distributed noise. This has been achieved by the modified beamforming method with regard to cepstrum domain is used. It is noteworthy that the cepstrum has the ability to detect periodic pulse signal in noise. Numerical simulation and experiments are performed to verify the method. Results show that the proposed technique is quite powerful for localizing the faults in noisy environments. The method also required less microphones than conventional beamforming method.

빔형성 방법을 이용한 경사 반사계수 측정

주형준,강연준 한국소음진동공학회 2003 한국소음진동공학회 논문집 Vol.13 No.6

A method using beamforming algorithm has been developed to measure oblique incidence reflection coefficients of sound absorption materials. MUSIC(multiple signal classification) method detects the angles of incidence and reflection. By separating the incident and reflected waves using beamforming method, the reflection coefficient is calculated. Spatial smoothing technique Is also used to reduce the coherence between the incident and reflected waves. Numerical and experiment results are performed to verify the accuracy of proposed method.

실내 공간에서의 음원 탐지 방법

김양한,최영철 한국소음진동공학회 2002 한국소음진동공학회 논문집 Vol.12 No.7

Identification of noose sources, their locations and strengths, has been taken great attention. The methods that can identify noise sources normally assume that noise sources are located in a free field. However, the sound in a reverberant field consists of that coming directly from the source plus sound reflected or scattered by the walls or objects in the field. In contrast to the exterior sound field. reflections are added to sound field. Therefore, we haute to consider the reverberation effect on the source identification method. The main objective of this paper is to identify noise source in the reverberant field. At fist, we try to identify noise sources in a rigid wall emc;psire using the beamforming method. In many cases of practical interest, the wall has admittance so that random reflections occur in an enclosure. In this paper, we assumed the complex reverberant field in the enclosure to be the sum of plane caves with random Incidence and magnitude. Then we try to explain effects of reverberant field at interior source identification.

수중방사소음 예측을 위한 빔형성 방법 기반 추진기 캐비테이션 음원준위 추정

김용현(Yong-Hyun Kim),설한신(Hanshin Seol),이정훈(Jeung-Hoon Lee),정홍석(Hongseok Jeong) 한국소음진동공학회 2021 한국소음진동공학회 논문집 Vol.31 No.2

In general, the prediction of underwater radiated noise requires source level information. This study proposes a method for the source level estimation of propeller cavitation based on the beamforming method. The proposed method obtains the source level information by determining the source strength corresponding to the estimated cavitation position. As the solution of the minimization problem can be determined analytically rather than numerically, it has the advantage of fast computational time. The proposed method is verified through a model-scale test conducted in a large cavitation tunnel of Korea Research Institute of Ships and Ocean Engineering. The estimated source level of the propeller cavitation matches well with a transfer-function-based method in the frequency band that satisfies the far-field. In addition, another method for reducing the computational time is considered through determining the source level from the cavitation position and sound pressure level.

마이크로폰 어레이를 이용한 모형로켓의 이동 궤도 추적

고영주,이재형,정욱진,하재현,최종수 한국항공우주학회 2014 한국항공우주학회 학술발표회 논문집 Vol.2014 No.4

본 연구에서는 초속 50 미터 속도로 움직이는 모형로켓 모터에서 방사된 제트 소음을 어레이로 측정하여 빔형성 기법으로 이동 궤적을 추정하였다. 실외 환경에서 고속으로 움직이는 점음원을 구현하기 위해 로켓모터가 이동하는 선형 궤도를 설치하였고, 로켓의 방사 소음을 마이크로폰 어레이로 측정하였다. 소음원의 속도와 위치 변화는 음파 전파 경로 및 시간에 영향을 주며 빔형성 결과에 오차를 발생하기 때문에 측정 환경을 고려한 신호 모델링을 통해 어레이 성능을 시뮬레이션 하였다. 음원의 이동이 위치 추정에 미치는 영향을 평가하기 위해 시간 변화에 따른 주파수 분석을 수행하였다. 어레이 시험을 통해 나온 빔파워로부터 선형으로 움직이는 소음원의 위치를 판별하였으며 시간-주파수 그래프로부터 측정환경에 대한 반사파의 영향을 확인하였다. In this research, the linear trajectory of model rocket motor with velocity of 50 m/s is estimated using emitted jet noise based on beamforming method. In order to measure the sound waves transmitted from a fast moving compact source, a model rocket motor is designed to move along a linear wire guide. The jet noise of the motor is measured with uniform linear array of microphones. Since the relative velocity of a moving acoustic source to receivers make an influence on the acoustic wave propagation path and time, the beamforming results in erroneous location of the source. Simulation of array performance has been conducted through a signal modeling under the measurement condition. To investigate the accuracy of beamforming due to the motion of the source, spectrograms of pressure data during array measurement are obtained. Beam power of array tests confirms the linear motion of the source and its spectrogram shows the mirror effect due to the ground reflection.

이동하는 운송체의 외부소음원 측정에 관한 실험적 연구

홍석호(Suk-Ho Hong),최종수(Jong-Soo Choi) 한국항공우주학회 2008 韓國航空宇宙學會誌 Vol.36 No.3

최근에 들어 이동하는 운송체의 외부에서 발생하는 소음의 위치를 판별하는 몇가지 방법들이 개발되었고, 운송체의 저소음화 설계과정에 적용되어 지고 있다. 빔형성법은 여러 개의 마이크로폰으로부터 측정된 신호의 위상차를 이용하여 소음원의 위치를 판정하는 기법으로서 비교적 복잡한 환경하에서도 좋은 결과를 얻을 수 있는 기법으로 확인되고 있다. 본 연구에서는 빔형성법을 적용하여 승용차가 주행할 때 발생하는 소음원의 위치를 판별하는 연구를 수행하였다. 정지된 소음원의 경우와는 달리 이동하는 소음원의 경우는 도플러 효과에 의하여 측정된 신호가 변형되는데, 운송체의 움직이는 속도와 마이크로폰들과의 상대적 거리차를 이용하여 보정해주는 방법을 적용하였다. 움직이는 운송체에서 발생되는 소음원은 여러 가지로 분류될 수 있는데, 본 실험에서 수행된 조건하에서는 이중 타이어 소음과 엔진에서 발생하는 소음이 가장 큰 것으로 측정되었다. Several experimental techniques for identifying the noise sources distributed over a moving vehicle have been developed recently and are used to design a low noise vehicle. The beamforming method, which uses phase information between several microphones to localize the source position, is proved to be one of the promising techniques applicable even under complicated test environments. In this study a beamforming algorithm is developed and applied to measure the dominant noise sources on a passenger car passing by. Unlike the acoustic signals from a stationary noise source, the sound generated from a moving source is distorted due to the Doppler effects. The information about the speed and relative position of the vehicle are used to eliminate the Doppler effects from the measured acoustic signal by using a de-Dopplerization algorithm. The noise generated from a moving vehicle can be grouped in many ways, however, tire noise and the noise generated from the engine are distinguishable at the speeds being tested.