• 한국정밀공학회지
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• 제17권1호
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• pp.83-92
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• 2000

Sound intensity method is well known as a visualization technique of sound field or sound propagation in noise control. Sound intensity or energy flux is a vector quantity which describes the amount and the direction of net flow of acoustic energy at a given position. Especially two dimensional sound intensity method is very useful in evaluating periodic characteristics and acoustic propagation mode of noise source. In this paper, we have studied the noise source Identification, acoustic sound field analysis, and characteristics of noise source of rotary compressor and scroll compressor for air conditioner using complex sound intensity method. Also we proposed a now method of time domain analysis which is used in evaluating of position of noise source in rotary and scroll compressor in this paper This paper presents the advantage, simplicity and economical efficiency of this method by analysing the characteristics of noise source with two dimensional complex sound intensity simultaneously.

• 소음진동
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• 제10권4호
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• pp.669-678
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• 2000

This paper reviews the improved moving frame acoustic holography (MFAH) method and its application. Moving frame acoustic holography was originally proposed to increase the aperture size and the spatial resolution of hologram by using a moving line array of microphones. The hologram of scanned plane can be obtained by assuming the sound field to be product of spatial and temporal information. Although conventional MFAH was only applied to sinusoidal signals, it allows us to visualize the noise generated by moving noise sources by employing a vertical line array of microphones affixed to the ground. However, the sound field generated by moving sources becomes different from that of stationary ones due to the movement of the sources. Firstly, this paper introduces the effect of moving noise sources on the obtained hologram by MFAH and the applicability of MFAH to the visualization of moving sources. Secondly, this paper also reviews improved MFAH that can visualize a coherent narrow band noise and a pass-by noise. The practical applicability of the improved MFAH was demonstrated by visualizing tire noise during a pass-by test.

• 한국생산제조학회지
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• 제22권4호
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• pp.723-729
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• 2013

The contraction and expansion noise of a refrigerator are investigated, and some effective methods are proposed to reduce the level and occurrence frequency of noise. First, the noise of a refrigerator is measured to estimate the frequency spectrum and occurrence frequency of noise. Second, a sound visualization was conducted using an acoustic camera to determine the location of the noise source. From the results, it was observed that the internal part mainly producing noise was the third shelf in the freezer room. A method to estimate the acceleration on the location of the noise source is introduced to analyze the contraction and expansion noise precisely and accommodate experimental convenience. Noise reduction methods such as the replacement of the existing shelf with glass shelves, adoption of rail slides, and increase of roughness on the contact surface of the shelf are proposed and tested.

• Journal of Welding and Joining
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• 제14권6호
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• pp.37-47
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• 1996

An ultrasonic testing uses the directivity of the ultrasonic wave which propagates in one direction. The directivity is expressed as the relationship between the propagate direction and its sound pressure. The directivity of ultrasonic wave is related to determination of testing sensitivity, scanning pitch and defect location. This paper investigated the directivity of ultrasonic wave, which scattered from slit defect located in heat-affected zone (HAZ) in butt joint using visualization method. The directivity of shear waves scattered from slit defect were different according to probe direction (far defect, near defect) and probe position (forward movement, maximum echo position, backward movement). The difference of directivity of reflection wave was existed between 2 MHz and 4 MHz angle probes. In the case of 2 MHz angle probe, the directivity of reflection wave was appeared sharp form because of the relation wave length and defect size.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1479-1486
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• 2000

This paper introduces the improved moving frame acoustic holography (MFAH) method and its application. MFAH allows us to visualize the noise generated by moving noise sources by employing a vertical line array of microphones affixed to the ground. The sound field generated by moving sources is different from that of stationary ones due to the movement of the sources. Therefore the measured sound pressure by the microphone on the ground has to be processed so that it cooperates the effect of the movement. This paper discusses the effect of moving noise sources on the obtained hologram by MFAH. This assures the applicability of MFAH to the visualization of moving sources. This paper also reviews the improved MFAH that can visualize a coherent narrow band noise and a pass-by noise. The practical applicability of the improved MFAH was demonstrated by visualizing tire noise during a pass-by test.

• 한국디자인학회:학술대회논문집
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• 한국디자인학회 2005년도 춘계 학술발표대회 논문집
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• pp.54-55
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• 2005

• 음성과학
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• 제10권4호
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• pp.63-71
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• 2003

This study aims to experiment on learning French intonation, based on the visualization of melody, which was employed in the early sixties to reeducate those with communication disorders. The visualization of melody in this paper, however, was used to the foreign language learning and produced successful results in many ways, especially in learning foreign intonation. In this paper, we used the PitchWorks to visualize some French intonation samples and experiment on learning intonation based on the bitmap picture projected on a screen. The students could see the melody curve while listening to the sentences. We could observe great achievement on the part of the students in learning intonations, as verified by the result of this experiment. The students were much more motivated in learning and showed greater improvement in recognizing intonation contour than just learning by hearing. But lack of animation in the bitmap file could make the experiment nothing but a boring pattern practices. It would be better if we can use a sound analyser, as like for instance a PitchWorks, which is designed to analyse the pitch, since the students can actually see their own fluctuating intonation visualized on the screen.

• Journal of Advanced Marine Engineering and Technology
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• 제24권4호
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• pp.515-525
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• 2000

A new acoustic field visualization technique is introduced in this study. Small particles of which density is small enough to follow up the air used for the noise field visualization. In order to quantify the noise, PIV(Particle Imaging Velocimetry) has been constructed. When the driving frequency is in the vicinity of the resonance frequency of the simplified 2-dimensional muffler system, an acoustic streaming is shown and of which velocity distribution is obtained through PIV technique. It is experimentally proved that the present technique is able to visualize and quantify the acoustic fields.

• 한국철도학회논문집
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• 제19권3호
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• pp.271-279
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• 2016

팬터그래프의 공력소음은 열차가 고속으로 주행할 때 발생하는 소음의 주요한 원인이다. 본 연구에서는 팬터그래프에 의한 공력소음 기여도를 분석하기 위하여 차세대고속열차(HEMU-430X)를 이용하여 시험을 수행하였다. 실제차량에서의 팬터그래프에 의한 소음의 주파수 특성을 분석하기 위하여, 350km/h와 400km/h 주행 시 전체차량의 음장가시화를 144채널 마이크로폰 어레이를 이용하여 수행하였다. 음장가시화 분석결과 팬터그래프의 소음은 250~400Hz 대역의 저주파 소음이 주로 기여함을 확인하였다. 또한 팬터그래프의 소음 기여도를 분석하기 위하여 팬터그래프의 올림 및 내림 시 소음도 차이를 단일 마이크로폰 시험을 통하여 비교분석하였다. 단일 마이크로폰 시험을 통한 팬터그래프 소음의 주요 주파수 특성은 315~400Hz와 1000~1250Hz 대역임을 확인 하였으며 이는 기존의 연구 결과 및 음장가시화 결과와 잘 일치하였다.

• 한국콘텐츠학회논문지
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• 제8권6호
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• pp.121-129
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• 2008

소리를 이용한 정보의 표현 방법은 무형의 특징을 가진 매체를 이용하여 어떠한 방법을 통하여 구체적인 형태를 이끌어 내는가에 대한 문제에서 시작된다. 이 과정에서 소리를 매개체로 이용하여 구성되는 오디오-비쥬얼 시스템은 청각적 소재를 이용한 시각적 표현이라는 방법적 측면에서 감각 기관의 연계에 대한 역할을 맡고 있는 부분에서 청각의 시각화라는 비 구체적 감각에 대한 구체화라는 변형의 의미를 갖는다. 오디오-비쥬얼 시스템 형태를 통한 작품을 표현하는데 있어 기존에 사용되던 프로그래밍을 통한 비규칙적 프로시쥬얼(Procedure)적 동적(動的) 이미지 또는 비동적(非動的) 이미지를 사용한 표현 방법에서 시각적 출력 방법의 제한으로 인한 표현 방법의 제한이 생겨날 수 있는 부분에 있어 동적 이미지를 이용한 오디오-비쥬얼 시스템을 통하여 소리를 매체로 한 다양한 표현 결과물을 이끌어낼 수 있다. 본 논문에서는 동적 이미지를 사용한 오디오-비쥬얼 시스템을 통해 다양한 청각적 소재의 시각화 방법 및 소리를 이용한 애니메이션 표현법의 새로운 대안을 제시한다.