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Measurement of the normal acoustic impedance using beamforming method
선종천,신창우,주형준,백순권,강연준 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.8
A beamforming technique is introduced to measure the normal acoustic impedance at both normal and oblique incidence in a free field. In the proposed method, microphone array signals are decomposed into incident and reflected waves using an adaptive nulling algorithm, which is a type of beamforming algorithm. The acoustic impedance can then be calculated from the ratio of these two signals. To obtain better results, the pressure vector commonly used in array signal processing is replaced with the transfer function vector between each microphone, and the white Gaussian noise is suppressed by a wavelet shrinkage technique. For an accurate experimental setup, the incident and reflected angles are estimated by the multiple signal classification method with spatial smoothing. The experiments conducted in a semi-anechoic room show that the proposed method is efficient and accurate in measuring the normal acoustic impedance of sound-absorbing materials under a free field condition.
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 ㎐.
자유 음장 조건에서 개선된 빔형성 방법을 이용한 흡음재의 수직 입사 표면 임피던스 측정
신창우(Shin, Chang-Woo),선종천(Sun, Jong-Choen),강연준(Kang, Yeon-June),백순권(Paik, Soon-Kwon) 한국소음진동공학회 2008 한국소음진동공학회 논문집 Vol.18 No.6
An improved beamforming method is proposed to measure the surface impedance of absorbing materials in a free field. It is possible to estimate the surface impedance by decomposing measured signals into incident and reflected signals by using the spatial filter matrix of the beamforming method. Wavelet do-noising techniques which reduce the white Gaussian noise are applied to improve the results. Phase calibration method is also used to improve the results of the measured surface impedance in a low frequency range. The results of the normal incidence experiments that are performed in a semi-anechoic chamber are verified by comparing with those of the standard test method that is presented in ASTM E1050. The proposed method is found to be reliable to measure the surface impedance for frequencies higher than 400 Hz.
Practical Implementation and Open Issues of Active Noise Control in the Automotive Industry
Seonghyeon Kim(김성현),M. Ercan Altinsoy,Young Man Kim(김영만),Dongjin Kim(김동진),Soonkwon Paik(백순권),Jun-Woo Lee(이준우),Shinkyu Kang(강신규),Dong Joo Lee(이동주),Bitna Lee(이빛나),Soyoun Moon(문소연) 한국소음진동공학회 2020 한국소음진동공학회 학술대회논문집 Vol.2020 No.11