• Title/Summary/Keyword: Boundary Noise

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Noise control of a slab using the laminated composite damping system (평판 부착형 제진시스템을 이용한 구조기인 소음 저감에 관한 연구)

  • Hwang, Jae-Seung;Kim, Gwang-Young;Hong, Geon-Ho
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2009.04a
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    • pp.403-407
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    • 2009
  • It is reported that the heavy weight floor impact noise of a slab system is very sensitive to the location of microphone and impact load. In addition, it is known that the aspect raio, thickness and boundary condition of a slab also have great effect on the noise induced by impact load. However, the effect has been mainly evaluated by experimental test and numerical analysis is nearly performed to verify the effect quantitatively. In this study, the effect of the aspect ratio, thickness and boundary condition on the heavy weight floor impact noise is examined through numerical analysis for simple rectangular slab system. The results show that the thickness and boundary condition have a strong correlation with the noise of the slab, on the contrary, the aspect ratio has little relation with the noise.

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Depth-map Preprocessing Algorithm Using Two Step Boundary Detection for Boundary Noise Removal (경계 잡음 제거를 위한 2단계 경계 탐색 기반의 깊이지도 전처리 알고리즘)

  • Pak, Young-Gil;Kim, Jun-Ho;Lee, Si-Woong
    • The Journal of the Korea Contents Association
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    • v.14 no.12
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    • pp.555-564
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    • 2014
  • The boundary noise in image syntheses using DIBR consists of noisy pixels that are separated from foreground objects into background region. It is generated mainly by edge misalignment between the reference image and depth map or blurred edge in the reference image. Since hole areas are generally filled with neighboring pixels, boundary noise adjacent to the hole is the main cause of quality degradation in synthesized images. To solve this problem, a new boundary noise removal algorithm using a preprocessing of the depth map is proposed in this paper. The most common way to eliminate boundary noise caused by boundary misalignment is to modify depth map so that the boundary of the depth map can be matched to that of the reference image. Most conventional methods, however, show poor performances of boundary detection especially in blurred edge, because they are based on a simple boundary search algorithm which exploits signal gradient. In the proposed method, a two-step hierarchical approach for boundary detection is adopted which enables effective boundary detection between the transition and background regions. Experimental results show that the proposed method outperforms conventional ones subjectively and objectively.

Development of internal inflow/outflow steady mean flow boundary condition using Perfectly Matched Layer for the prediction of turbulence-cascade interaction noise (난류-캐스케이드 상호작용 소음 예측을 위한 Perfectly Matched Layer 을 이용한 내부 입/출구 정상유동 경계조건의 개발)

  • Kim, Dae-Hwan;Cheong, Cheol-Ung
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2012.04a
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    • pp.521-526
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    • 2012
  • It is essential for the accurate time-domain prediction of broadband noise due to turbulence-cascade interaction to develop inflow/outflow boundary conditions to satisfy the following three requirements: to maintain the back ground mean flow, to nonreflect the outgoing disturbances and to generate the specified input gust. The preceding study(1) showed that Perfectly Matched Layer (PML) boundary condition was successfully applied to absorb the outgoing disturbances and to generate the specified gust in the time-domain computations of broadband noise due to interaction of incident gust with a cascade of flat-plates. In present study, PML boundary condition is extended in order to predict steady mean flow that is needed for the computation of noise due to interaction of incident gust with a cascade of airfoils. PML boundary condition is originally designed to absorb flow disturbances superimposed on the steady meanflow in the buffer zone. However, the steady meanflow must be computed before PML boundary condition is applied on the flow computation. In the present paper, PML equations are extended by introducing source term to maintain desired mean flow conditions. The extended boundary condition is applied to the benchmark problem where the meanflow around a cascade of airfoils is predicted. These illustrative computations reveal that the extended PML equations can effectively provide and maintain the target meanflow.

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Development of Internal Inflow/outflow Steady Mean Flow Boundary Condition Using Perfectly Matched Layer for the Prediction of Turbulence-cascade Interaction Noise (난류-캐스케이드 상호작용 소음 예측을 위한 Perfectly Matched Layer을 이용한 내부 입/출구 정상유동 경계조건의 개발)

  • Kim, Dae-Hwan;Cheong, Cheol-Ung
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.22 no.7
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    • pp.685-691
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    • 2012
  • It is essential for the accurate time-domain prediction of broadband noise due to turbulence-cascade interaction to develop inflow/outflow boundary conditions to satisfy the following three requirements: to maintain the back ground mean flow, to nonreflect the outgoing disturbances and to generate the specified input gust. The preceding study showed that perfectly matched layer(PML) boundary condition was successfully applied to absorb the outgoing disturbances and to generate the specified gust in the time-domain computations of broadband noise due to interaction of incident gust with a cascade of flat-plates. In present study, PML boundary condition is extended in order to predict steady mean flow that is needed for the computation of noise due to interaction of incident gust with a cascade of airfoils. PML boundary condition is originally designed to absorb flow disturbances superimposed on the steady meanflow in the buffer zone. However, the steady meanflow must be computed before PML boundary condition is applied on the flow computation. In the present paper, PML equations are extended by introducing source term to maintain desired mean flow conditions. The extended boundary condition is applied to the benchmark problem where the meanflow around a cascade of airfoils is predicted. These illustrative computations reveal that the extended PML equations can effectively provide and maintain the target meanflow.

Car Interior and Exterior Multi-domain Noise Analysis using Power Flow Boundary Element Method (PFBEM을 이용한 자동차 실내외 다영역 공간의 소음해석)

  • Kim, Jong-Do;Hong, Suk-Yun;Lee, Ho-Won;Kwon, Hyun-Wung
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.05a
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    • pp.489-493
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    • 2007
  • Mmulti-domain noise analysis method using Power Flow Boundary Element Method(PFBEM) has been developed successfully. Some applications are introduced. several examples. PFBEM is a numerical analysis method formulated by applying Boundary Element Method(BEM) to Power Flow Analysis(PFA). PFBEM is very powerful in predicting noise level in medium-to-high frequency ranges. However there are restrictions in analyzing the coupled structures and multi-media. In this paper, an analysis method for multi-domain acoustic problems in the diverse acoustic fields is suggested. And the developed method is applied to the car interior and exterior multi-domain noise analysis.

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Environmental Noise Evaluation of the Boundary Areas for 1200MW Combined Cycle Power Plant (1200MW 복합화력 발전소가 부지경계에 미치는 환경소음 예측)

  • 이현;김연환;김희수;배용채;김성휘
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2001.05a
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    • pp.1056-1061
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    • 2001
  • This paper describes the evaluation of noise influence of residental and boundary areas from power plant noise sources of 1200MW combined cycle power plant. Noise assessments are carried out by based on the ISO 3744, ISO 9613-1 and ISO 9613-2 to predict the noise distribution to satisfy the recommended noise level at specific locations and to calculate properly the octave noise power of main noise sources such as power transformers. air-intakes, stacks.

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Good Choice of Positions and Impedances of Absorptive Materials for Effective Interior Noise Control (흡음재의 적절한 위치 및 임피던스 선정을 통한 효율적인 실내 소음 제어)

  • 조성호;김양한
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.05a
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    • pp.791-796
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    • 2003
  • Some basic guidelines for changing non-uniform boundary condition in an acoustically small cavity are presented. In this paper, modal summation technique is used to represent inside sound field. From this formulation, corner effect is defined and proposed. The corner in a cavity is good position for changing boundary condition effectively. Impedance circle with same absorption coefficient is defined to find appropriate impedance of absorptive material for better noise control performance.

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The Influence of Design Factors of Sonar Acoustic Window on Transfer Function of Self Noise due to Turbulent Boundary Layer (소나 음향창의 설계 인자가 난류 유동 유기 자체 소음의 전달 함수에 미치는 영향 해석)

  • Shin, Ku-kyun;Seo, Youngsoo;Kang, Myengwhan;Jeon, Jaejin
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2012.10a
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    • pp.568-574
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    • 2012
  • Turbulent boundary layer noise is already a significant contributor to sonar self noise. For developing acoustic window of sonar system to reduce self noise, a parametric study of design factors of acoustic window is presented. Distance of sensor array from acoustic window, material and damping layer are studied as design factors to influence in the characteristics of the transfer function of self noise. As the result these design factors make change the characteristics of transfer function slightly. Among design factors the location of sensor array is most important parameter in the self noise reduction.

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An Enhancement of Removing Noise Branches by Detecting Noise Blobs (잡영블랍 검출에 의한 잡영가지 제거 방법의 개선)

  • 김성옥;임은경;김민환
    • Journal of Korea Multimedia Society
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    • v.6 no.3
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    • pp.419-428
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    • 2003
  • Several methods have been studied to prune the parasitic branches that cause unfortunately from thinning a shape to get its skeleton. We found that the symmetric path finding method was most efficient because it followed the boundary pixels of the shape just once. In this paper, its extended method is proposed to apply to removing the noise branches that protrude out of the boundary of a segmented or extracted shape in a given image. The proposed method can remove a noise branch with one-pixel width and also remove the noise branch that includes a round shape called a noise blob. The method uses a 4-8-directional boundary-following technique to determine symmetric paths and finds noise branches with noise blobs by detecting quasi-symmetric paths. Its time complexity is a linear function of the number of boundary pixels. Interactively selectable parameters are used to define various types of noise branches flexibly, which are the branch - size parameter and the blob-size parameter. Experimental results for a practical shape and various artificial shapes showed that the proposed method was very useful for simplifying the shapes.

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Normal Mode Vibrations of a Beam with a Nonlinear Boundary Condition (비선형 경계조건을 가진 보의 정규모드진동)

  • 김현기;이원경
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1998.04a
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    • pp.392-398
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    • 1998
  • In order to check the validity of nonlinear normal modes of continuous, systems by means of the energy-based formulation, we consider a beam with a nonlinear boundary condition. The initial and boundary e c6nsl of a linear partial differential equation and a nonlinear boundary condition is reduced to a linear boundary value problem consisting of an 8th order ordinary differential equations and linear boundary conditions. After obtaining the asymptotic solution corresponding to each normal mode, we compare this with numerical results by the finite element method.

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