• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.634-637
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• 2007

A weighted sound pressure level has been used to evaluate sounds test or sound quality test for a refrigerator up to present but the customer had different satisfactions of refrigerator sounds with different listening position. It means that there was a sound directivity caused by a position of fan or compressor. In this paper, we proposed a sound power spectrum guideline that represents total sound of refrigerator.

• 대한의용생체공학회:의공학회지
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• 제10권2호
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• pp.151-156
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• 1989

본 연구에서는 폐 및 기관지 질환 환자에 대한 객관적인 진단을 위한 폐음분석 시스템을 설계하였다. 적응 필터링 기법에 의하여 순수한 폐음을 분리하였고 이의 power spectrum을 구하기 위하여 TMS320C25 DSP 칩과 IBM PC를 사용해서 폐음 분석기를 구성하였다. 실험결과 적응 격자 위너 필터는 10차의 적은 차수로도 분리가 가능하였고 정상 폐음은 100-200 Hz, 급성 섬유성 폐렴폐음(crackle)은 100-400 Hz, 기관지 협착증(wheeze)폐음은 150-600 Hz에서 주파수범위를 갖는 power spectrum의 양상을 통해 각각 패턴 분류할 수 있었다.

• 한국소음진동공학회논문집
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• 제12권8호
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• pp.581-588
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• 2002

Precise highway traffic noise simulation and reduction require the accurate data for sound power levels omitted by vehicles, varied to road surface, traffic speed, vehicle types and makers, different from countries to countries. In this study, we have elaboratively measured Korea highway traffic noise and parameters affecting noise levels at the nearside carriageway edge. From numerical simulation using the measured results for highway traffic noise, we propose not only two correction factors to enhance the accuracy of Korea highway traffic sound power estimation using ASJ Model-1998 but also its typical power spectrum according to road surface type. The measured and predicted highway traffic noise levels using the proposed sound power show little difference within 1 dB.

• 한국소음진동공학회논문집
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• 제15권6호
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• pp.687-696
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• 2005

Acoustic power spectrum of the upstream and downstream sound field due to an isotropic frozen turbulent gust impinging on a cascade of flat plate airfoils are computed by using a analytic formulation derived from Smith's method, and Whitehead's LINSUB codes. A parametric study of the effects on sound power of the number of blades and turbulence length scale is performed with an emphasis on analyzing the characteristics of sound power spectrum. Through the comparison of the computed results of sound power, it is found that acoustic power spectrum from the 2-D cascade subject to a ingested turbulence can be categorized into two distinct regions. one is lower frequency region where some spectral components of turbulence do not contribute to the cut-on acoustic modes and therefore the effect of the cascade geometry is more dominant ; the other is higher frequency region where all of spectral components of turbulence make contributions to cut-on acoustic modes and thus acoustic power is approximately proportional to the blade number.

• 한국음향학회지
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• 제22권8호
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• pp.660-669
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• 2003

본 논문은 음원 근처의 홀로그램 평면에서 측정된 음압에 대한 상호 파워 스펙트럼으로부터 홀로그램 평면에서의 음압 분포를 구하고 획득된 음장을 공간 변환하여 음원의 음장을 구하기 위한 이론을 설명하였으며, 홀로그램 평면에서의 상호 파워 스펙트럼으로부터 모든 지점에서의 음압을 구하기 위해 비선형 방정식에 대한 Taylor 급수를 전개하고 Newton-Raphson 법을 이용하여 계산하는 방법과 음원 영역으로의 역방향 전파시 발생되는 오차를 줄이기 위한 파수 필터를 제시하였다. 무한 배플 내의 원판형 진동체 수중 음원에 대한 모의실험을 통해 결과를 고찰하고 제시된 이론을 검증하였다.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1994년도 FIFTH WESTERN PACIFIC REGIONAL ACOUSTICS CONFERENCE SEOUL KOREA
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• pp.752-757
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• 1994

Very often, one would like to have visual image of mechanical or acoustical events such as musical sound and transient vibrations. Conventional methods to visualize the signal, such as power spectrum, do not normally allow to cultivate the signal of interests due to their inherent limitation on transient signals. Other than the conventional method, one could use an instantaneous frequency which can reveal the variation of frequency in terms of time. Nevertheless it is quite sensitive to noise and can not resolve the frequency components of signals; normally produces additional components other than those of the signals. In this paper, we introduce the Wigner-Ville spectrum to see the transient characteristics of signal, especially musical sound and transient mechanical vibration signatures. For musical sound, several popular western classic music have been selected for the analysis. For the transient mechanical signature, the signals obtained from the car door experiment and the beam experiment are interpreted in terms of Wigner-Ville spectrum. Results demonstrate the visual expressions of transient signals; musical sound and vibrations.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.1075-1079
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• 2002

This paper presents a result of sound transmitting system with power line communication technique, Sound transmitting system is a transmitter which transmits modulated audio signal to power to power line and receiver which is capable of detesting it with earphone or speaker. It has been evaluated with the frequency characteristics and spectrum analysis. And, from the result of evaluation on the developed system, we confirm the superior sound transmitting characteristics, and the possibility of application on a language laboratory.

• 조명전기설비학회논문지
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• 제18권3호
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• pp.128-134
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• 2004

본 연구에서는 전력선통신 기술을 이용하여 전송주파수에 음성신호를 변조한 후 전력선으로 전송하고 전력선으로부터 수신 및 복조하여 변조된 음성신호를 검출하는 음향전달 시스템을 제작하였다. 제작된 시스템으로부터 변복조 및 주파수 특성을 분석하여, 어학실습 교육을 위한 용도로서의 활용 가능성을 평가하였다. 그 결과 전달된 음향 신호가 최적상태는 아니지만 어학실습 교육용으로 청취하기에 충분한 수준으로 판단되었다.

• 한국수산과학회지
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• 제14권4호
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• pp.265-268
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• 1981

길이 250cm, 간격 10cm의 25개의 수동계 직선배열 hydrophone을 0, $\pm1$의 거형파 weighting을 부가하여 신호와 weighting과의 convolution을 구하고 이것을 동기가산하는 방법으로 얻는 방향검출과 spectrum분석은 그 실현방법을 증대시키고 정현파 weighting을 부가하는 것보다 3dB정 도 낮으나 지향성을 준 방향보다 타방향의 spectrum성분의 Power level을 적어도 16dB 정도 이상 억제할 수가 있었다. 또 신호까지 0, $\pm1$의 거형파로 바꾸는 경우는 전술한 성분을 적어도 8 dB 이상 억제할 수 있었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.1273-1279
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• 2001

Precise highway traffic noise simulation and reduction require the accurate data for sound power levels emitted by vehicles, varied to road surface, traffic speed, vehicle types and makers, different from countries to countries. In this study, we have elaboratively measured domestic highway traffic noise and parameters affecting noise levels at the nearside carriageway edge. From numerical simulation using the measured results for highway traffic noise, we propose not only two correction factors to enhance the accuracy of highway traffic sound power estimation using ASJ Model-1998 but also its typical power spectrum according to road surface type. The measured and predicted highway traffic noise levels using the proposed sound power shows little difference within 1 dB.