• Title, Summary, Keyword: Acoustic Finite Element Analysis

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A Vibration Mode Analysis of Resilient Mounting System and Foundation Structure of Acoustic Enclosure using Finite Element Method (유한요소법을 이용한 음향차폐장치용 탄성마운트 시스템 및 받침대의 진동모드 해석)

  • 정우진;배수룡;함일배
    • Journal of KSNVE
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    • v.9 no.3
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    • pp.493-501
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    • 1999
  • The vibration modes of resilient mounting system and foundation structure which support diesel engine/generator set and acoustic enclosure walls play an important role in the vibration transmission process. So, it is necessary to perform vibration mode analysis of resilient mounting system and foundation structure. For some reasons, if the vibration modal analysis of resilient mounting system and foundation structure of acoustic enclosure could be simultaneously done by finite element method, it would be very efficient approach. In this paper, vibration modal analysis method using finite element method for multi stage mounting system having n d.o.f model was proposed. Vibration analysis of single and double stage resilient mounting system was performed to verify the validity of the proposed method. Also frequency response results were compared in case of rigid foundation model and finite element foundation model which was compared with experimental modal analysis results.

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Vibro-acoustic Analysis of Adjoined Two Rooms Using 3-D Power Flow Finite Element Method (3차원 파워흐름유한요소법을 이용한 인접한 두 실내에서의 진동음향 해석)

  • Kim, Sung-Hee;Hong, Suk-Yoon;Kil, Hyun-Gwon;Song, Jee-Hun
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.20 no.1
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    • pp.74-82
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    • 2010
  • Power flow analysis(PFA) methods have shown many advantages in noise predictions and vibration analysis in medium-to-high frequency ranges. Applying the finite element technique to PFA has produced power flow finite element method(PFFEM) that can be effectively used for analysis of vibration of complicated structures. PFADS(power flow analysis design system) based on PFFEM as the vibration analysis program has been developed for vibration predictions and analysis of coupled structural systems. In this paper, to improve the function of vibro-acoustic coupled analysis in PFADS, the PFFEM has been extended for analysis of the interior noise problems in the vibro-acoustic fully coupled systems. The vibro-acoustic fully coupled PFFEM formulation based on energy coupled relations is extended to structural system model by using appropriate modifications to structural-structural, structural-acoustic and acoustic-acoustic joint matrices. It has been applied to prediction of the interior noise in two room model coupled with panels, and the PFFEM results are compared to those of statistical energy analysis(SEA).

Multi-Domain Structural-Acoustic Coupling Analysis Using the Finite Element and Boundary Element Techniques

  • Ju, Hyeon-Don;Lee, Shi-Bok
    • Journal of Mechanical Science and Technology
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    • v.15 no.5
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    • pp.555-561
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    • 2001
  • A new approach to analyze the multi-domain acoustic system divided and enclosed by flexible structures is presented in this paper. The boundary element formulation of the Helmholtz integral equation is used for the internal fields and the finite element formulation for the structures surrounding the fields. We developed a numerical analysis program for the structural-acoustic coupling problems of the multi-domain system, in which boundary conditions such as the continuity of normal particle velocity and sound pressure in the structural interfaces between Field 1 and Field 2 are not needed. The validity of the numerical analysis program is verified by comparing the numerical results with the experimental ones. Example problems are included to investigate the characteristics of the coupled multi-domain system.

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Finite Element Analysis for Acoustic Characteristics of Piezoelectric Underwater Acoustic Sensors (압전 수중음향센서 음향특성의 유한요소해석)

  • 김재환;손선봉;조철희;조치영
    • The Journal of the Acoustical Society of Korea
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    • v.20 no.1
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    • pp.68-76
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    • 2001
  • Sonar is the system that detects objects and finds their location in water by using the echo ranging technique. In order to have excellent performance in variable environment, acoustic characteristics of this system must be analyzed accurately. In this paper, based on the finite element analysis, modeling and analysis of acoustic characteristics of underwater acoustic sensors are preformed. Couplings between piezoelectric and elastic materials, and fluid and structure systems associated with the modeling of piezoelectric underwater acoustic sensors are formulated. In the finite element modeling of unbounded acoustic fluid, IWEE (Infinite Eave Envelop Element) is adopted to take into account the infinite domain. When an incidence wave excites the surface of Tonpilz underwater acoustic sensor, the scattered wave on the sensor is founded by satisfying the radiation condition at the artificial boundary approximately. Based on this scattering analysis, the electrical response of the underwater acoustic sensor under incidence, so called RVS (Receiving Voltage Signal) is founded accurately. This will devote to design Sonar systems accurately.

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Application of Substructure Synthesis Method for Analysis of Acoustic System (음향계의 해석을 위한 부분구조합성법의 적용)

  • 오재응;고상철;조용구
    • Journal of KSNVE
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    • v.7 no.5
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    • pp.737-746
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    • 1997
  • The substructure synthesis method is used for making it easy to analyze vibration systems generally in vibration field. In the past, this method has been to be used mainly because of shortage of computer memory and CPU time. But recently this method is used for analyzing complex structure or identifying the characteristics of systems precisely. The purpose of this study is to develop acoustic substructure synthesis method that can be applied to acoustic modal analysis of complex acoustic systems. Acoustic modal analysis method to be introduced here is a method that analyze acoustic natural mode shape of the complex acoustic system by the principle of CMS(component mode synthesis method). This paper describes the acoustic modal analysis of the acoustic finite element model of simple expansion pipe by acoustic substructure synthesis method. The resutls of acoustic modal analysis analyzed by Acoustic substructure synthesis method and the results by FEM(finite element method) shows good agreement.

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Research on Vibro-acoustic Coupled Analysis using Power Flow Finite Element Method (파워흐름유한요소법을 이용한 진동음향 연성해석 연구)

  • Kim, Sung-Hee;Kwon, Hyun-Wung;Hong, Suk-Yoon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.767-770
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    • 2006
  • To predict vibrational energy density of simple structural-acoustic coupled systems in medium-to-high frequency ranges, Power Flow Finite Element Method(PFFEM) is used, and PFFEM sofiware, PFADS has been developed for the vibration predictions and analysis of coupled system structures in medium-to-high frequency ranges. However, it needs to consider vibro-acoustic coupled analysis to get more accurate results. Prior to implement vibro-acoustic coupled analysis functions in PFADS, research on vibro-acoustic coupled analysis using PFFEH is performed for simple models. These predictions include the indirect transmission path associated, and also the direct transmission path, and the formulation is extended to structural system model by using appropriate modifications to structural-acoustic and acoustic-acoustic joint matrices. Concerning the waves in plate and acoustic, it is possible to calculate the structural-acoustic full matrix of a model using PFFEM, and the formulations developed are implemented for two rooms surrounded by plates.

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An Analysis of Internal & External Duct Acoustic Fields by Using a Finite Element Method (유한요소법을 이용한 도관 내부 및 외부 음장해석)

  • 이재규;이덕주
    • Journal of KSNVE
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    • v.3 no.2
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    • pp.169-178
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    • 1993
  • Internal & External duct acoustic fields are calculated by using a finite element method. The geometry is assumed as an axisymmetric duct. External acoustic field; outside the duct, and combined internal & external acoustic fields are solved. For both cases a far field's nonreflecting boundary condition is enforced by using a wave envelope element, which is a kind of finite element. First, a pulsating sphere and an oscillating sphere problem are calculated to verify the external problems, and the results are compared with exact solutions. When the wave envelope element is applied at the far boundary, the calculated finite element solutions show good agreements with the exact solutions. Secondly, the combined internal & external duct acoustic fields are calculated and visualized when monopole sources are distributed inside the duct. It is observed that the directivity of sound intensity outside the duct is beaming toward the axis for high frequency sources.

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A Study on Dynamic and Acoustic Behavior of Beel Type Structure Using Finite Element Method (유한요소법을 이용한 종형 구조물의 동적거동 및 음향거동에 관한 연구)

  • 정석주
    • Journal of KSNVE
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    • v.6 no.4
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    • pp.447-456
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    • 1996
  • Dynamic characteristics of the bell-type structure including acoustic effects and transient dynamic problems were analyzed numerically. Natural frequencies, mode shapes and transient dynamic analysis used the finite element method with 3-D general shell element. Mode shapes and stress distributions of transient dynamic analysis were expressed by computer graphics. The method using this study was evaluated by comparision of theoretical results at reference papers(14), (15) and the experimental test using Fast Fourier Transform analyzer. Vibrational modes governing acoustic characteristics of the typical bell-type structure depended on the first flexural mode(4-0 mode) and the second flexural mode(6-0 mode). Asymmetric effects by Dangiwas, acoustic holes gave rise to beat frequencies, and the Dangjwa was found to be most effective. When impact load acted on the bell, stress concentration occured at the rim part of bell. It was found that the bell type structure should be designed thickly at the rim part in order to prevent impact load from stress concentration.

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Multi-scale finite element analysis of acoustic waves using global residual-free meshfree enrichments

  • Wu, C.T.;Hu, Wei
    • Interaction and multiscale mechanics
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    • v.6 no.2
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    • pp.83-105
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    • 2013
  • In this paper, a multi-scale meshfree-enriched finite element formulation is presented for the analysis of acoustic wave propagation problem. The scale splitting in this formulation is based on the Variational Multi-scale (VMS) method. While the standard finite element polynomials are used to represent the coarse scales, the approximation of fine-scale solution is defined globally using the meshfree enrichments generated from the Generalized Meshfree (GMF) approximation. The resultant fine-scale approximations satisfy the homogenous Dirichlet boundary conditions and behave as the "global residual-free" bubbles for the enrichments in the oscillatory type of Helmholtz solutions. Numerical examples in one dimension and two dimensional cases are analyzed to demonstrate the accuracy of the present formulation and comparison is made to the analytical and two finite element solutions.

Acoustic Analysis and Design of a Direct-Radiator-Type Loudspeaker (직접방사형 스피커의 음향특성 해석및 설계)

  • 김준태;김정호;김진오
    • Journal of KSNVE
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    • v.8 no.2
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    • pp.274-282
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    • 1998
  • A systematic procedure for designing a direct-radiator-type loudspeaker has been developed, based on the numerical vibro-acoustic analysis and the Taguchi method. The finite-element model of the speaker cone has been used to calculated the vibration response of the cone excited by the voice coil. The vibration displacement of the speaker cone has been converted into the vibration velocity and used as a boundary condition for the acoustic analysis. The acoustic frequency characteristics of the loudspeaker have been calculated by the boundary element method. The numerical results have been verified by the experiments carried out in an anechoic chamber. Some design parameters have been selected by using the Taguchi method, and the variations of the acoustic characteristics due to the changes of the parameter values have been examined using the numerical model.

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