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마운트계의 실험적 설계변경을 위한 전달함수분리법의 개발
정의봉,조영희 한국소음진동공학회 1997 소음 진동 Vol.7 No.5
Many investigations about the dynamic analysis of the structural system based on the BBA(Building Block Approach) method which predict dynamic characteristics of synthesized structures from each structure. But it is actually sometimes difficult to remove mounts from structures. In this paper, TFSM(The Transfer Function Separation Method) is developed which can predict dynamic characteristics of separated structures from the data of vibrational experiment of the synthesized structures. By combining TFSM with BBA, this paper also proposes the method which can predict dynamic characteristics of mount-modified structure without removing mounts from structures. And the proposed method is verified by the experimental data of plates.
정의봉,안세진,장호엽,장진혁 한국소음진동공학회 2001 한국소음진동공학회 논문집 Vol.11 No.3
An exact spectrum with no leakage error could be obtained when the period of the signal coincides perfectly with the record length. However, the record length will be determined regardless of the period of signal. The Leakage error due to this problem will give a distorted spectrum. In the conventional research, the method was proposed to estimate the three parameters, frequency, amplitude and phase angle, from the spectrum data for an undamped sinusoidal signal. In this paper, some techniques are proposed to estimate frequency, amplitude and damping ratios from the frequency response functions for damped signals. The validation of the proposed techniques is verified by several numerical examples.
정의봉,정호경,안세진,윤상돈 한국음향학회 2003 韓國音響學會誌 Vol.22 No.5
음향 인텐시티는 근접한 두 개의 마이크로폰으로부터 얻어지는 음압의 크로스스펙트럼으로부터 얻어진다. 크로스스펙트럼은 이산 푸리에 변환에 의해 얻어지는데 이는 기록시간과 신호의 주기가 일반적으로 일치하지 않기 때문에 누설오차의 발생을 피할 수 없다. 그러므로 기존의 FFT 해석기로부터 얻어지는 음향 인텐시티는 왜곡된 값을 보여준다. 본 논문에서는 단일주파수를 가지는 조화 신호에 누설오차가 발생한 경우 푸리에 변환된 데이터를 규정한다. 또한 왜곡된 데이터로부터 누설오차의 영향을 제거하는 방법을 제안한다. 제안한 방법의 타당성을 보이기 위해 몇 가지 수치해석 예를 보인다. Acoustic intensity is usually estimated by the cross-spectrum of acoustic pressure at two adjacent microphones. The cross-spectrum calculated by digital Fourier transform technique will unavoidably have leakage error since the period of signal will not be usually coincident with record length. Therefore, the acoustic intensity estimated by the conventional FFT analyzer will show distorted value. In this paper, the expression of the Fourier transformed data of a harmonic signal with a single frequency is formulated when there is leakage error. The method to eliminate the effect of leakage error from the contaminated data is also proposed. Some numerical examples show the validation of the proposed method.