• Title/Summary/Keyword: 고체음

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Reduction of airborne and structure-borne noise of naval ship pump (함정용 펌프의 공기음 및 고체음저감)

  • 김현실;김재승;강현주;김봉기;김상렬
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.05a
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    • pp.942-947
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    • 2002
  • In this study, reduction of airborne and structure-borne noise of naval ship pump is presented. Since piping system arrangement such as valve location, flexible joint, pipe diameter and elbow location, discharge basin affect greatly on the noise measurement, care must be taken to minimize the unnecessary noise from the piping system. It is shown that structure-borne noise of the motor with single resilient mount system exceeds criterion. Therefore, it is concluded that double resilient mount system is inevitable. Two kinds of mount is studied for upper mount; spring and rubber type. Although both mounts show good performance at low frequency including rpm frequency, 63Hz, spring mount is found to be inadequate at high frequency, because spring coil acts as a path for SBN.

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고출력 펨토초 레이저와 플라즈마의 상호작용을 통한 극고속 X선 펄스의 발생

  • Jeong, Sang-Yeong;Hwang, Seok-Won;Lee, Hae-Jun
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.08a
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    • pp.38-38
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    • 2010
  • 낮은 세기의 레이저와 정지한 전자가 반응하면 전자는 레이저 전기장 세기에 비례하여 가속되며 레이저의 파장과 같은 파장의 빛을 낸다. 반면, 레이저의 세기가 일정 수준을 넘으면 전자의 속도가 빛의 속도에 가까워지게 되어 가속이 둔화되는 현상이 나타나며, 더 이상 전기장의 세기와 가속도가 비례하지 않게 된다. 이러한 비선형적인 전자의 운동이 레이저 기본 파장의 조화파(harmonic)를 발생시키는데, 이를 상대론적 비선형 톰슨 산란(relativistic nonlinear Thomson scattering, RNTS)이라고 한다. 단일 전자를 가정한 경우 RNTS에 의해 아토초($10^{-18}$ 초) 길이의 X선 펄스가 발생하는 것이 시뮬레이션 연구를 통해 잘 알려졌다. [1] 그러나, 실제 실험에서 적용할 수 있는 것은 단일 전자가 아니라 고체, 플라즈마, 전자 빔 등의 전자 덩어리이다. 전자덩어리를 구성하는 각각의 전자가 아토초 펄스를 발생시더라도 각각의 펄스 간에 결맞음(coherence) 조건이 맞지 않으면 아토초 펄스는 발생되지 않는다. 또한, 강한 세기의 펄스를 얻는데도 결맞음은 중요하다. 이 연구에서는 결맞음 조건으로 얇은 타깃에 대한 거울 반사 조건, 즉 레이저가 얇은 타깃에 입사되며 거울의 반사 조건을 만족하는 위치에 검출기(detector)를 위치시키는 방법을 제안하였다. 박막이 충분히 얇을 경우 각각의 전자에 대하여 레이저가 발사되어 타깃에 맞고 검출되기까지의 시간이 거의 일치하게 된다. 거울 반사 조건에 의한 아토초 펄스 발생은 particle-in-cell 방법을 통한 시뮬레이션으로 검증되었다. 결맞음 조건을 위한 얇은 타깃으로는 박막과 나노선 배열(nanowire array)을 사용하였다. 전자들 간의 쿨롱(Coulomb) 힘은 결맞음이 유지되는 것을 방해하는데, 박막에 비해 나노선 배열이 쿨롱 힘의 영향을 적게 받기 때문에 결맞음이 더 잘 유지된다.

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A Study on the Computer Program for the Shipboard Noise Prediction - using Statistical Energy Analysis - (선박 소음 예측 전산 프로그램의 개발에 관한 연구 -통계적 에너지 해석법을 이용한-)

  • Sa-Soo Kim;Ku-Kyun Shin;Hong-Gi Lee
    • Journal of the Society of Naval Architects of Korea
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    • v.28 no.2
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    • pp.293-306
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    • 1991
  • During the last few years recommendations or regulations concerning permissible noise levels on shirts have been issued by the authorities in most countries. For these reasons the need for useful and accurate noise prediction computer programs has been emphasized. A noise prediction program can make it possible to find the most economical solution to achieve a certain noise requirement. This paper attempts to develop a noise prediction computer program using statistical energy analysis(SEA). In this paper, the SEA is used to predict the sound transmission loss for airborne noise and the vibration amplitude of the panel consisting of ship spaces such as floor, wall, and ceiling for structureborne noise. And in order to verify the prediction, a small passenger vessel, G/T120 tons, is selected. It has been shown that the prediction is capable of giving results in good practical agreement with measurements and therefore it is useful for predicting the nolle levels in ships and establishing the countermeasures at early design stage.

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The Efficiency of a Spring Mass Dampers System for the Control of Vibrations and Structure-borne Noise (진동 및 고체음 제어를 위한 스프링 매스댐퍼계의 효과)

  • ;;;;Heiland, D.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1993.04a
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    • pp.147-147
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    • 1993
  • All types of dynamic excitation, periodical, pulse or transient in vertical, horizontal or all three directions can be effectively reduced by vibration isolation systems. Typical elements for vibration isolation control are spring units consisting of a group of helical compression springs. In all cases of shock, transient or random excitation energy absorbing dampers have to be added to the spring units in order to reduce system response in the frequency range near the natural frequency of the isolation system. The same isolation system of spring units and viscos-dampers has been used since 1979 for passive protection of buildings and structures has been proved to by very advantageous for vibration and structure borne noise control. Not only because of high vertical flexibility of the spring units, compared for example with typical rubber or neoprene mounts out also because of the horizontal of flexibility, which can be adapted by modifying the spring dimensions to nearly every requirement. It is just normal to use the same basic elements for passive isolation as for active isolation.

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An Empirical Noise Prediction on Board (경험식을 이용한 선박 소음 예측법)

  • Gyung-M. Kim;Nho-S. Kim;Hyun-J. Kang;Jae-S. Kim
    • Journal of the Society of Naval Architects of Korea
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    • v.28 no.2
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    • pp.268-274
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    • 1991
  • The methods of prelimiuary noose prediction by Janssen, Buiten, etc are introduced. The distribution of noise levels in newly built ships are investigated. A new procedure for noise prediction is proposed which reflects the results of the investigations. The dominant noise souroes(M/E, D/G) are regarded as one virtual source. The structureborne transmission loss are divided into vortical and horizontal components and the latter component depends on the number of decks as well as the number of frames. The all considered cabins are standardized with typical cabins which have the same acoustic properties. The measured and predicted noise levels are compared In the tables.

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A study of noise source identification on plate excited structure borne sound by acoustic intensity method (음향인텐시티법에 의한 고체진동 가진판의 소음원 검출에 관한 연구)

  • 오재응;김상헌;홍동표;이찬홍
    • Journal of the korean Society of Automotive Engineers
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    • v.8 no.4
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    • pp.43-55
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    • 1986
  • In the studies of noise reduction, it is important to know the generation mechanism of noise in order to identify the noise source. The relation between the structural vibration and the radiated sound is very complex and so this paper deals with a simplified radiation model that was originally developed as a verification tool for the acoustic intensity measurement procedure. As the first step for the identification of the noise source, this study deals with the noise evaluation by measuring sound pressure. On the next step, the acoustic radiational pattern is determined by the acoustic intensity method and this paper established that the acoustic intensity method is effective on the detection of noise. In the study, furthermore, the method could be used to predict the change in the sound radiational characteristics with the attachment of absorber and could be used in determining the attachment position.

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A Study on the Noise.Vibration Characteristics of Differential Gear according to the Materials (차동기어의 재질별 진동.소음 특성에 관한 연구)

  • 최은오
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.6 no.2
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    • pp.67-75
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    • 1997
  • The noise . vibration characteristics of Hypoid gears which were made from three seperate materials(SCM, TSCM, SNCM) under the identical process were investigated for the sake of durability improvement of differential gear compatible with low level noise gear set. For this study, we developed a rig experimental equipment which can perform close noise.vibration experiment of differential gear. Consequently, we could analyze the noise.vibration characteristics of final reduction gear by materials, and also we observed changes in both metallic structure and hardness according to the materials of pinion gear. In addition to this, the correlation between the vibration of the differential gear and the interior noise of the passenger vehicles was proved by analyzing the results of rig vibration experiment and field noise test.

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Estimation of Vibrational Power Supplied From Vibration Source to Supporting Structure (진동원으로부터 지지구조물에 전달되는 진동 파워의 추정방법)

  • 김재철;이종원
    • Journal of KSNVE
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    • v.8 no.2
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    • pp.306-312
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    • 1998
  • This paper proposes a method for estimating the vibrational power supplied by a machine that generates excitation force to its supporting structure via the coupling points. The basis of the method is that the vibrational power can be calculated using the mechanical impedance and the velocity at the coupling points on the supporting structure. First, a method is described to estimate the mobilities at the coupling points when the machine is not separable from the supporting structure, then the vibrational power is calculated using the estimated mobilities and measured velocities at the coupling points. The mobilities are estimated from the result of impulsive testing of the coupled structure. The method is investigated using an experimental model. The estimated and measured values of the mobilities and the vibrational power are compared. It is shown that the estimated values agree well with the measured values.

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The Verification on Effect of Sound Absorption Tunnel for Elevated Railway in Cholla Line (전라선 고가교 방음터널 효과검증)

  • Kim, Byoung-Sam;Lee, Tae-Keun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.05a
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    • pp.667-672
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    • 2007
  • The source of wayside noise for the train are the aerodynamic noise, wheel/rail noise, and power unit noise. The major source of railway noise is the wheel/rail noise caused by the interaction between the wheels and rails. The Structure borne noise is mainly a low frequency problem. The train noise and vibration nearby the elevated railway make one specific issue. In this paper, the train noise and structure borne noise by train are measured. From the results, we investigated the effect on the sound absorption tunnel for elevated railway.

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SBN(Structure-borne Noise) Reduction of Resiliently Mounted Machinery and Effect of Foundation Impedance (탄성지지된 장비의 고체음저감 및 받침대 임피던스효과)

  • Kim, Hyun-Sil;Kim, Jae-Seung;Kang, Hyun-Ju;Kim, Bong-Ki;Kim, Sang-Ryul
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.05a
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    • pp.423-426
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    • 2007
  • In this paper, vibration reduction of resiliently mounted machinery and effect of the foundation impedance is studied. SBN (Structure-borne noise) reduction through the mount is analyzed by assuming that the system is modeled as a mass-spring system, while the impedance of the floor is included in the prediction. The comparison of the SBN difference through the mount between predictions and measurements show that the slopes are similar in the case of single-mount system, while the measurements differs significantly from the predictions in the case of the double-resilient system.

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