지향 특성을 이용한 Beam-former의 고속 수렴 알고리즘

김학윤 청주대학교 산업과학연구소 2005 産業科學硏究 Vol.22 No.3

This paper describes a fast convergence algorithm to perform the projection and iterative learning between independent component analysis(ICA) and null beam-forming. The proposed method consist of the following two sections: first, subband-ICA-based BSS section with estimation on the direction of arrival(DOA) of the sound source, second, null beam-forming section based on the estimated DOA. The alterative of learning between ICA and the null beam-forming can realize the fast convergence optimization.

쇄골 중간부 골절후 불유합 및 지연 유합의 원인

윤정로,심재익,김택선,이성종,김영배,김학준,안국환,장재영,홍명표 대한골절학회 2002 대한골절학회지 Vol.15 No.4

쇄골 중간 1/3 부위의 골절은 치료 결과가 양호하여 보존적 치료가 원칙적으로 받아 들어지고 잇으며 불유합에 대한 빈도도 낮은 것으로 되어 있다. 그러나 최근 전위 및 단축의 정도가 심할 경우 높은 불유합의 결과와 불량한 임상 결과를 보고하고 있어 이런 예에 대해선 수술적 치료를 권장하고 있다. 저자들은 단축 및 전위의 정도와 불유합의 연관성을 알아보고자 하였다. 연구 대상 및 방법 : 1993년 2월부터 2002년 1월까지 본원에 내원 했던 성인 중간부 쇄골 골절 환자 194명 중 완전 전위를 보인 78례를 조사하여 이중 63례를 대상으로 분석하여 후 향적 연구를 시행하였다. 4개월 추시 후에도 방사성 사진상 유합 소견이 관찰되지 않으면 불유합의 유의성을 알아보고자 하였다. 결 과 : 63례 중 불유합 및 지연 유합을 소견을 보인 환자는 15(23%)례였다. 골유합을 보인 48례의 단축은 평균 8.6㎜(2㎜-17㎜)였고, 전위는 평균 9.7㎜(2-22㎜)였다 .불유합 및 지연 유합을 보였던 15례에서 단축은 평균 14.5㎜(3㎜-37㎜), 전위는 평균 17.3㎜(4-25㎜)였다. 18㎜이상 단축이 있었던 경우 불유합의 발생과는 통계학적으로 유의성을 나타내었고(Fisher's exact test, p<0.01), Chi-square test상 16㎜ 이상의 전위를 보였던 경우 불유합 발생과 통계학적으로 의미가 있었다(p<0.01). 결 론 : 쇄골 골절 특히 중간 1/3의 골절은 비교적 보존적 치료에 결과가 좋은 것으로 되어 있으나, 전위 및 단축이 심한 경우 불유합에 대한 가능성이 높이 때문에 보다 경과 관찰시 유합의 진행이 없으면 적극적인 치료를 고려해야한다. Purpose : Because the prognosis of the mid 1.3 clavicle fracture is good, the conservative treatment with a figure of 8 bandage is the gold standard and the nonunions are rare. However, recently surgical treatment is recommended when the shortening and displacement is severe because of the high nonunion rate and the poor clinical result. This study was undertaken to evaluate that the shortening and displacement at fracture site are associated with the development of nonunion. Materials and Methods : We analysed the 194 fractures of mid 1/3 clavicle in adults which had been treated conservatively from February 1993 to January 2002 and did the retrospective study. Of these, 78 cases were originally in the middle third of the clavicle and had been completely displaced. We reviewed 63 of these cases. The shortening and displacement at the fracture site was measured on the initial roentgenogram. And the analysis of the patients' chart was done for another predisposing nonunion factors. Nonunion and delayed union are considered to be present when there has been little or no progression of clinical or radiographic healing at a minimum of 4 months after injury. Results : 15 of the 63 cases had developed nonunion.. The average 8.6㎜(2㎜-17㎜) shortening and average 9.7㎜(2-22㎜) in the union patients. The average 14.5㎜(3㎜-37㎜) shortening and average 17.3㎜(4-25㎜) in the nonunion patients. We found that initial shortening ≥18㎜(Fisher's exact test, p<0.01) and initial displacement ≥ 16㎜(Chi-square test. p<0.01)at the fracture site were significantly associated with the development of nonunion. Conclusion : The conservative treatment with figure-80-bandage is the gold standard in the clavicle middle one third fracture. However, the nonunion is commonly occurs in the cases of more of severely shortened and displaced fractures. If there are no signs of callus formation and the patient complains of pain after several week, osteosynthesis should be considered.

음장의 잔향 시간 제어 시스템 설계에 관한 연구

김학윤 청주대학교 산업과학연구소 2022 産業科學硏究 Vol.39 No.2

In this study, a system that modifies the acoustic characteristic of a sound reproduction field rh an arbitrary reverberation time-frequency characteristic is developed. And then was examined a signal processing method that controls the reverberation time of each frequency band independently, and designed an algorithm that adjusts the reverberation characteristic of sound field to a desired characteristic. A computer simulation of the algorithm shows that it can make a highly precise approximation. The validity of this method, which creates envelopment and natural reverberation, was clarified through listening test applied to some real sound fields.

개선된 상호상관계수를 이용한 음원의 도래 방향 추정 기법

김학윤 청주대학교 2016 産業科學硏究 Vol.33 No.2

We propose a new method to estimate the direction of arrival(DOA) based on the improved cross correlation coefficient(ICC). Prior to the proposal, we investigate the relation between the spatial sensitivity of the ICC and the microphone arrangement to show the fact that the spatial sensitivity of the ICC can have the resolution not only for an azimuthal angle but for an angle of elevation in case where the microphones are arranged to have the front directions of those microphones not to belong to the identical plane. We carry out the computer simulation of the DOA estimation based on ICC and show effectiveness of the proposed method.

IPD와 ILD를 이용한 음원의 도래 방향 추정

김학윤 청주대학교 2007 産業科學硏究 Vol.25 No.1

Human being can estimate not only azimuth but also elevation angle of sound source based on two ears. Namely, the human auditory function is an important element to communicate with others in a noisy environment. Therefore humans operate estimation of direction of arrival and speech separation based on binaural listening. In this report, Estimation of direction of arrival is proposed using the ILD(Interaural Phase Difference) and IPD(Interaural Level Difference). This method estimates direction of arrival using IPD and ILD in the frequency domain. Also, computer simulation is performed to confirm this method after making waveform at the fixed place. And the estimation result is good.

3차원 음상제어 알고리즘

김학윤,김희석 청주대학교 산업과학연구소 1997 産業科學硏究 Vol.15 No.2

The 3-D sound image is achieved controlling a perception of the direction, distance and spatial. There are two method to reproduce it. One is the transaural, to be reproduced by loudspeakers, and Another is the binaural, to be reproduced by headphones. This paper discusses the 3-D sound image control algorithm, and the method to reproduce it by Headphones and Loudspeakers.

다채널-다점 제어 주파수 영역 역 필터 설계

김학윤 청주대학교 산업과학연구소 2023 産業科學硏究 Vol.41 No.1

In order to realize the multi-channel sound field reproduction system, it is indispensable to design inverse filters that remove the effect of room transfer functions. Among the methods for designing inverse filters, the frequency domain method has the advantage of faster computation time and memory saving compared to the time domain method. However, the method of designing in the frequency domain has the drawback of requiring the inverse filter to be designed as a FIR filter. Therefore, this paper proposes a new inverse filter design method to overcome these problems. Furthermore, to evaluate the usefulness of the proposed method, computer simulations were performed using real environmental data. The simulation results showed a reduction in squared error of approximately 3-10dB. Additionally, when comparing the SNR of the reproduced sound using a 16-channel 6-point control system between the conventional method and the proposed method, an improvement of over 12dB was observed.

초소형 스피커 유닛의 특성 평가 방법에 관한 연구

김학윤 청주대학교 2017 産業科學硏究 Vol.35 No.1

In this paper, we describes measuring methods of small size speaker units for mobile equipment. Although conventional measurements utilize the standard enclosure or baffle specified in IEC 60268, these acoustical loads are not suitable for this purpose because they are too large to simulate housings of ordinary mobile equipment, for example mobile telephone sets. This paper presents two sorts of acoustical loads. One is a medium sized enclosure with satisfactory data repeatability. The other is a tube load with satisfactory small acoustical diffraction.

3차원 음상 제어 시스템 구현

김학윤 청주대학교 산업과학연구소 1998 産業科學硏究 Vol.16 No.-

A 3-D spatializer algorithm has been developed. The spatializer simulates the auditory expenence of one or more sound sources abitrarily located around a listener. The basic idea is to reproduce the acoustical signals at the two ears that would occur in a normal listening situation. This is accomplished by convolving each source signal with the pair of HRTFs that correspond to direction of the source. Then, the real time processor system was designed. Thus system is based on the Texas Instrument TMS320C40-based signal processor system that perform direct- and frequency dependent filtering and ITD for each image source, the recursive reverberation filtering, and the HRTF processing.

실내음장을 구축하기위한 탄성판의 특성평가

김학윤 청주대학교 산업과학연구소 2001 産業科學硏究 Vol.19 No.1

The acoustic characteristic of elastic plate considered the wave of sound must be evaluated to copy the room sound-field precisely In this paper, we consider approximate evaluation value which is able to indicate sound characteristic of the elastic plate fixed Baffle Quantitatively, and then evaluate the acoustic characteristic about the radiation admittance one of the sound characteristics of the elastic plate.