• Title/Summary/Keyword: coupled acoustics

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A Study on the Reverberation Characteristics of Coupled Spaces (음향적으로 결합된 공간의 잔향특성변화에 관한 연구)

  • Jeong, Dae-Up;Kim, Ji-Young;Choi, Young-Ji
    • Journal of Korean Association for Spatial Structures
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    • v.8 no.3
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    • pp.53-63
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    • 2008
  • In this study, the reverberation characteristics of coupled spaces were investigated using a scale model. Two rooms were connected through an acoustically transparent opening known as an aperture. The acoustic characteristics of the coupled room by varying three parameters, the aperture opening size, the absorption ratio between the two rooms and the locations of the secondary room, were measured and analysed. The results indicated that a reverberant secondary room, produced large variations of the acoustics in the main room and an absorptive secondary room was effective to provide systematic control of the acoustics in the main room. The reverberant secondary room should be located at the rear of the stage and the aperture opening ratio over 6.25% produced large variations of the acoustics in the main room. However, the aperture opening ratio over 25% had no effect on variations of the acoustics in the main room. The absorptive secondary room should be located at the rear of the audience areas and the aperture opening ratio over 3.13% produced large variations of the acoustics in the main room.

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Variable Acoustics in performance venues- A review (공연장에서의 가변음향에 대한 고찰)

  • Hyon, Jinoh;Jeong, Daeup
    • The Journal of the Acoustical Society of Korea
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    • v.40 no.6
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    • pp.626-648
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    • 2021
  • Domestically, demands for multi-purpose performance venues which accommodate various performance genres have increased. However, those venues have limited capability and confined to a primary performance. The present work investigated various methods for controlling the acoustics of room for required performance genres by reviewing aurally presented and published materials. The method of varying the acoustics of a space is called Variable Acoustics, and adjusted in either passive and active ways. Passive control encompasses variable absorption, variable volume, coupled volume, and canopy reflectors, where the acoustics of a room is controlled in an architectural way. Active control includes In-line, Regenerative, and Hybrid systems where the acoustics of a room is manipulated electronically. The mechanism and application of each passive control system in existing venues are reviewed and their pros and cons are discussed. Also, the concept of each active systems and product applications are looked at through literature reviews. Lastly, some considerations that need to be taken into in the planning and design stage of a multi-purpose hall using Variable Acoustics are suggested.

Hybridal Method for the Prediction of Wave Instabilities Inherent in High Energy-Density Combustors (2): Cumulative Effects of Pressure Coupled Responses on Cavity Acoustics

  • Lee, Gil-Yong;Yoon, Woong-Sup
    • International Journal of Aeronautical and Space Sciences
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    • v.7 no.2
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    • pp.33-41
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    • 2006
  • Theoretical-numerical approach of combustion instability in a specific rocket engine is conducted with parametric response functions. Fluctuating instantaneous burning rate is assumed to be functionally coupled with acoustic pressures and have a finite or time-varying amplitudes and phase lags. Only when the amplitudes and phases of combustion response function are sufficiently large and small respectively, the triggered unstable waves are amplified.

Advanced Computational Dissipative Structural Acoustics and Fluid-Structure Interaction in Low-and Medium-Frequency Domains. Reduced-Order Models and Uncertainty Quantification

  • Ohayon, R.;Soize, C.
    • International Journal of Aeronautical and Space Sciences
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    • v.13 no.2
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    • pp.127-153
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    • 2012
  • This paper presents an advanced computational method for the prediction of the responses in the frequency domain of general linear dissipative structural-acoustic and fluid-structure systems, in the low-and medium-frequency domains and this includes uncertainty quantification. The system under consideration is constituted of a deformable dissipative structure that is coupled with an internal dissipative acoustic fluid. This includes wall acoustic impedances and it is surrounded by an infinite acoustic fluid. The system is submitted to given internal and external acoustic sources and to the prescribed mechanical forces. An efficient reduced-order computational model is constructed by using a finite element discretization for the structure and an internal acoustic fluid. The external acoustic fluid is treated by using an appropriate boundary element method in the frequency domain. All the required modeling aspects for the analysis of the medium-frequency domain have been introduced namely, a viscoelastic behavior for the structure, an appropriate dissipative model for the internal acoustic fluid that includes wall acoustic impedance and a model of uncertainty in particular for the modeling errors. This advanced computational formulation, corresponding to new extensions and complements with respect to the state-of-the-art are well adapted for the development of a new generation of software, in particular for parallel computers.

The Analysis of Transmission Characteristics of Closed Structure with Internal Source Using FEM/BEM (유한.경계요소법을 이용한 내부음원을 갖는 닫힌 구조물의 차음 특성 해석)

  • Won, Sung-Gyu;Jung, Weui-Bong;Seo, Yeung-Soo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.05a
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    • pp.318-321
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    • 2005
  • In vibro-acoustic analysis, the commercial CAE tools, such as SYSNOISE, is usually used to take into account of the coupled effects of fluid acoustics and structural vibration. The acoustic field can be solved by either FEM or BEM, while the vibration field is usually solved by FEM. The interior or exterior acoustic problems with the coupled effects of the structural boundary could be solved by the commercial tools. The commercial tools, however, could not solve the problems in case that both the interior and exterior acoustic field is coupled with the structural boundary. In this paper, a realistic method based on FEM/BEM coupling scheme is presented to analyze the acoustic radiation from the internal source in a chamber to external acoustic field through elastic structural boundary. Several numerical examples are implemented to validate the developed program.

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Room Acoustic Properties of Coupled Rooms Connected by an Aperture in the Steady State Condition (정상상태조건에서의 개구부로 연결된 커플룸의 음향 특성)

  • Na, Hae Joong;Lim, Byoung-Duk
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.26 no.3
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    • pp.315-322
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    • 2016
  • Room acoustic properties of coupled rooms connected by an aperture has been analyzed using statistical acoustic model based on the diffused sound field assumption, which has limitation in dealing with the parameters such an room geometries and non uniform absorptivity of the boundary surfaces. In order to overcome these difficulties the acoustic diffusion model has been introduced, by which distribution of the acoustic energy density can be analyzed for various shapes and wall absorptivity. In this study acoustic properties of coupled rooms connected by an aperture(e.g. door) is analyzed using acoustic diffusion equation, which is solved numerically. The mean energy densities of two rooms obtained by the diffusion model are compared with those from the statistical model. The results show good agreement for various coupling aperture sizes and absorption coefficients. For a limiting case when the partition wall is substituted by an aperture and the two rooms eventually forms a single room, results of coupled room analysis using diffusion model show good agreement with those of a single room.

Substructure/fluid subdomain coupling method for large vibroacoustic problems

  • El Maani, Rabii;El Hami, Abdelkhalak;Radi, Bouchaib
    • Structural Engineering and Mechanics
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    • v.65 no.4
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    • pp.359-368
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    • 2018
  • Dynamic analysis of complex and large structures may be costly from a numerical point of view. For coupled vibroacoustic finite element models, the importance of reducing the size becomes obvious because the fluid degrees of freedom must be added to the structural ones. In this paper, a component mode synthesis method is proposed for large vibroacoustic interaction problems. This method couples fluid subdomains and dynamical substructuring of Craig and Bampton type. The acoustic formulation is written in terms of the velocity potential, which implies several advantages: coupled algebraic systems remain symmetric, and a potential formulation allows a direct extension of Craig and Bampton's method to acoustics. Those properties make the proposed method easy to implement in an existing finite element code because the local numerical treatment of substructures and fluid subdomains is undifferentiated. Test cases are then presented for axisymmetric geometries. Numerical results tend to prove the validity and the efficiency of the proposed method.

Visualization of Sound Field of Plate-Cavity Coupled System by Experimental Method (실험적 방법에 의한 평판-공동 연성계의 음장 가시화)

  • 김시문;김양한
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1997.04a
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    • pp.662-668
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    • 1997
  • Since the structural impedance is much greater than that of medium in the most cases, we often assume that the structure is rigid and that the structural vibration is independent of medium, i.e. we usually calculate the vibration of the structure first, and then obtain the radiation sound from it. This assumption is no longer satisfied when the structural stiffness is small or the fluid impedance is comparable to it. This situation often happens in underwater acoustics. Although many researchers have studied about structural-fluid coupling, we have difficulties in solving the problem analytically. Therefore the numerical method using powerful computation leads us to obtain the various coupling problem. To understand the physical coupling phenomena, visualization of sound field by a geometrically simple system(plate-cavity coupled system) is performed experimentally. Acoustic holographic method is used to estimate sound field.

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The effect of gravity and hydrostatic initial stress with variable thermal conductivity on a magneto-fiber-reinforced

  • Said, Samia M.;Othman, Mohamed I.A.
    • Structural Engineering and Mechanics
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    • v.74 no.3
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    • pp.425-434
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    • 2020
  • The present paper is concerned at investigating the effect of hydrostatic initial stress, gravity and magnetic field in fiber-reinforced thermoelastic solid, with variable thermal conductivity. The formulation of the problem applied in the context of the three-phase-lag model, Green-Naghdi theory with energy dissipation, as well as coupled theory. The exact expressions of the considered variables by using state-space approaches are obtained. Comparisons are performed in the absence and presence of the magnetic field as well as gravity. Also, a comparison was made in the three theories in the absence and presence of variable thermal conductivity as well as hydrostatic initial stress. The study finds applications in composite engineering, geology, seismology, control system and acoustics, exploration of valuable materials beneath the earth's surface.