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Acoustic Characteristics Of Perforated Dissipative And Hybrid Silencers
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Book Synopsis Acoustic Characteristics of Perforated Dissipative and Hybrid Silencers by : Iljae Lee
Download or read book Acoustic Characteristics of Perforated Dissipative and Hybrid Silencers written by Iljae Lee and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Acoustic characteristics of silencers filled with fibrous material (hence dissipative) are investigated. Following a theoretical and experimental analysis of a single-pass, perforated, dissipative concentric silencer, the study is extended to a hybrid silencer designed by combining dissipative and reflective (Helmholtz resonator) components. The ability to model these silencers relies heavily on the understanding of the acoustic behavior of the fibrous material and the perforations. Therefore, the present study has developed two experimental setups to measure: (a) the complex characteristic impedance and the wavenumber of the fibrous material with varying filling density and texturization conditions, and (b) the acoustic impedance of perforations in contact with the fibrous material, and with and without the mean flow. New empirical expressions are then provided for the acoustic impedance of perforations with varying porosity, hole diameter, wall thickness, mean flow rate, and the fiber characteristics. The experimental results illustrate that the presence of absorbent significantly increases both the resistance and reactance of the perforation impedance. The addition of mean flow is also shown in general to increase the resistance, while decreasing the reactance particularly at low porosities. The empirical expressions for the fiber acoustic properties and the perforation impedance are then integrated into the predictions of transmission loss. These predictions are based primarily on a three-dimensional boundary element method (BEM) developed in the present study, due to its ability to treat silencers with complex internals, in addition to one- and two-dimensional analytical approaches also introduced. Comparisons of predictions with the acoustic attenuation experiments support the proposed relationships for the properties of fibrous material and the perforation impedance. The influence of the internal geometry modifications of dissipative silencers, such as baffles and extended inlet/outlet, and the impact of connecting duct length between a pair of silencers, are investigated with BEM. Hence, the contributions of the present study include the development of methodologies for the measurement of acoustic properties of the fibrous material and the impedance of perforations, particularly in contact with the absorbent along with the resulting empirical expressions, thereby assisting towards analytical and computational design tools for the dissipative and hybrid silencers.
Book Synopsis Archives of Acoustics Quarterly by :
Download or read book Archives of Acoustics Quarterly written by and published by . This book was released on 2011 with total page 1004 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Transmission Loss of Silencers with Flow from a Flow-impedance Tube Using Burst Signals by : Hyunsu Kim
Download or read book Transmission Loss of Silencers with Flow from a Flow-impedance Tube Using Burst Signals written by Hyunsu Kim and published by . This book was released on 2011 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Acoustic performance of silencers is typically characterized by transmission loss both in the absence and presence of mean flow. The effects of flow on the acoustic characteristics of silencers, however, are not clearly established due to lack of appropriate experimental setups. In addressing this need, the present study develops a flow-impedance tube setup using burst signals for the transmission loss measurement in the presence of flow. By incorporating burst-signal separation with a long tube, an anechoic termination on the downstream side is achieved by separating the transmitted and reflected waves in time domain. Burst sine or burst random is used to enhance the signal-to-noise ratio. By applying wave decomposition in frequency domain on the upstream side, incident waves of the burst signals are effectively obtained. Also discussed in this study are (1) microphone calibration, (2) time domain editing functions, and (3) hydraulic losses either to improve the accuracy or the capacity of the transmission loss setup in the presence of flow. Using the new experimental setup, the effect of flow on various silencers is investigated. The acoustic performance of a Helmholtz resonator is shown to change dramatically in the presence of flow with an increase in the peak transmission loss frequency and a decrease in the magnitude. These varying acoustic characteristics of the Helmholtz resonator with flow are then explained using the lumped parameter model. Complex acoustic behavior of a dual Helmholtz resonator, a turbocharger resonator, and a Helmholtz resonator with leakage are also illustrated first without flow theoretically. The flow effect is then examined on these silencers as well as some additional key silencers such as expansion chamber, perforated tube silencers, and dissipative silencers using the flow-impedance tube setup. Hence, the primary contributions of the present study include (1) the development of methodologies for the transmission loss measurement in the presence of flow by implementing a flow-impedance tube setup and (2) the investigation of the acoustic performance of various silencers subject to flow, thereby establishing the impact of flow on their behavior which, in turn, is expected to provide guidelines toward their design.
Book Synopsis Acoustic Performance of Dissipative and Hybrid Silencers in Ducts with Large Transverse Dimensions by : Paul Timothy Williams
Download or read book Acoustic Performance of Dissipative and Hybrid Silencers in Ducts with Large Transverse Dimensions written by Paul Timothy Williams and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Modelling, Simulation and Data Analysis in Acoustical Problems by : Claudio Guarnaccia
Download or read book Modelling, Simulation and Data Analysis in Acoustical Problems written by Claudio Guarnaccia and published by MDPI. This book was released on 2020-06-23 with total page 584 pages. Available in PDF, EPUB and Kindle. Book excerpt: Modelling and simulation in acoustics is currently gaining importance. In fact, with the development and improvement of innovative computational techniques and with the growing need for predictive models, an impressive boost has been observed in several research and application areas, such as noise control, indoor acoustics, and industrial applications. This led us to the proposal of a special issue about “Modelling, Simulation and Data Analysis in Acoustical Problems”, as we believe in the importance of these topics in modern acoustics’ studies. In total, 81 papers were submitted and 33 of them were published, with an acceptance rate of 37.5%. According to the number of papers submitted, it can be affirmed that this is a trending topic in the scientific and academic community and this special issue will try to provide a future reference for the research that will be developed in coming years.
Book Synopsis Boundary Elements and Other Mesh Reduction Methods XXXVI by : X. W. Gao
Download or read book Boundary Elements and Other Mesh Reduction Methods XXXVI written by X. W. Gao and published by WIT Press. This book was released on 2013-12-11 with total page 569 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Conference on Boundary Elements and Mesh Reduction Methods (BEM/MRM) is recognised as the international forum for the latest advances in these techniques and their applications in science and engineering. Launched in 1978 the Conference continues to attract original contributions and has become the forum for their rapid dissemination throughout the international scientific community. Practically all new boundary element ideas have first appeared in the proceedings of these meetings.
Book Synopsis Boundary Elements and Other Mesh Reduction Methods XXXIV by : C.A. Brebbia
Download or read book Boundary Elements and Other Mesh Reduction Methods XXXIV written by C.A. Brebbia and published by WIT Press. This book was released on 2012-06-25 with total page 365 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains papers presented at the Thirty Fourth International Conference on Boundary Elements and other Mesh Reduction Methods (BEM/MRM), recognised as the international forum for the latest advances of these methods and their applications in science and engineering. The success of the meeting, since the first conference took place in Southampton, UK, in 1978, is an indication of the strength of the research being carried out by many different groups around the world. This continuous growth is a result of the evolution of the techniques from methods based on classical integral equations to techniques now covering a wide variety of mathematical approaches, the main objective of which is to reduce or eliminate the mesh. The mesh, a concept inherited from more primitive methods, such as finite differences and finite elements, is alien to the solution of the problem and dictated only by the limitations of first generation analysis techniques. Topics covered include: Advanced meshless and mesh reduction methods, Electrical engineering and electromagnetics, Fluid flow, Heat and mass transfer, Advanced structural applications, Dynamics and vibrations, Damage mechanics and fracture, Material characterisation, Advanced formulations, Computational techniques, Stochastic modelling, Emerging applications.
Book Synopsis EngOpt 2018 Proceedings of the 6th International Conference on Engineering Optimization by : H.C. Rodrigues
Download or read book EngOpt 2018 Proceedings of the 6th International Conference on Engineering Optimization written by H.C. Rodrigues and published by Springer. This book was released on 2018-09-13 with total page 1486 pages. Available in PDF, EPUB and Kindle. Book excerpt: The papers in this volume focus on the following topics: design optimization and inverse problems, numerical optimization techniques,efficient analysis and reanalysis techniques, sensitivity analysis and industrial applications. The conference EngOpt brings together engineers, applied mathematicians and computer scientists working on research, development and practical application of optimization methods in all engineering disciplines and applied sciences.
Book Synopsis Dissertation Abstracts International by :
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2005 with total page 768 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Journal of the Acoustical Society of America by : Acoustical Society of America
Download or read book The Journal of the Acoustical Society of America written by Acoustical Society of America and published by . This book was released on 2005 with total page 1042 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis 1D and Multi-D Modeling Techniques for IC Engine Simulation by : Angelo Onorati
Download or read book 1D and Multi-D Modeling Techniques for IC Engine Simulation written by Angelo Onorati and published by SAE International. This book was released on 2020-04-06 with total page 552 pages. Available in PDF, EPUB and Kindle. Book excerpt: 1D and Multi-D Modeling Techniques for IC Engine Simulation provides a description of the most significant and recent achievements in the field of 1D engine simulation models and coupled 1D-3D modeling techniques, including 0D combustion models, quasi-3D methods and some 3D model applications.
Book Synopsis Contribution to the Study of Dissipative Silencers by : Alexis Debray
Download or read book Contribution to the Study of Dissipative Silencers written by Alexis Debray and published by . This book was released on 2000 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt: [Résumé en anglais] This thesis is a part of the European project FLODAC (FLOw Duct ACoustic) and is dealing with two aspects of dissipative silencers. The expansion chamber is commonly used as a dissipative silencer. Here we propose an approximate model for such a system, in which the radial variations of the pressure and velocity in the air and in the porous lining are described by polynomials. These approximations allow the calculation of the reflexion and transmission coefficients which completely descibe the acoustic properties of the chamber at low frequency. Experimental results show the validity of such an approach. The presence of uniform flow in the air duct is introduced in the model. Agreement with experimental results is satisfying for the transmission coefficients. The study shows that for Mach numbers lower than 0.15, the effect of flow is already important. In particular, we note that the attenuation is lower in the sense of flow. The second aspect of the work is dealing with the effect of the vibration of the structure of the porous lining on the attenuation of a duet of infinite length. This part is partly using the work of E. Lesquins (SNECMA) and B. Brouard (LAUM). The porous material is described by the classical Biot theory. Several models are proposed. The geometry of the duct can be two-dimensional or circula rand two methods are investigated in order to solve the problem, i.e. determining the propagation constant for the different modes. Numerical simulations show that under certain circumstances structural vibrations can produce an important low frequency attenuation whereas under other circumstances the latter is lower. A first experimental study shows the validity of this work.
Book Synopsis Noise Control Engineering Journal by :
Download or read book Noise Control Engineering Journal written by and published by . This book was released on 2004 with total page 656 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Acoustics of Ducts and Mufflers by : M. L. Munjal
Download or read book Acoustics of Ducts and Mufflers written by M. L. Munjal and published by John Wiley & Sons. This book was released on 2014-02-04 with total page 379 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fully updated second edition of the premier reference book on muffler and lined duct acoustical performance Engine exhaust noise pollutes the street environment and ventilation fan noise enters dwellings along with fresh air. People have become conscious of their working environment. Governments of most countries have responded to popular demand with mandatory restrictions on sound emitted by automotive engines, and a thorough knowledge of acoustics of ducts and mufflers is needed for the design of efficient muffler configurations. This fully updated Second Edition of Acoustics of Ducts and Mufflers deals with propagation, reflection and dissipation/absorption of sound along ducts/pipes/tubes, area discontinuities, perforated elements and absorptive linings that constitute the present-day mufflers and silencers designed to control noise of exhaust and intake systems of automotive engines, diesel-generator sets, compressors and HVAC systems. It includes equations, figures, tables, references, and solved examples and unsolved exercises with answers, so it can be used as a text book as well as a reference book. It also offers a complete presentation and analysis of the major topics in sound suppression and noise control for the analysis and design of acoustical mufflers, air conditioning and ventilation duct work. Both the fundamentals and the latest technology are discussed, with an emphasis on applications. Deals with reactive mufflers, dissipative silencers, the frequency-domain approach, and the time-domain approach. Fully updated second edition of the premier reference book on muffler and lined duct acoustical performance, in one complete volume Presents original new research on topics including baffle silencers and louvers, 3D analytical techniques, and flow-acoustic analysis of multiply-connected perforated-element mufflers Includes a general design procedure to help muffler designers in the automotive industry, exhaust noise being a major component of automobile and traffic noise pollution Written by an expert with four decades’ experience in teaching to graduate students, publishing extensively in reputed international journals, and consulting with industry for noise control as well as designing for quietness
Book Synopsis Annual Index/abstracts of SAE Technical Papers by :
Download or read book Annual Index/abstracts of SAE Technical Papers written by and published by . This book was released on 2007 with total page 1218 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Propagation of Sound in Porous Media by : J.F. Allard
Download or read book Propagation of Sound in Porous Media written by J.F. Allard and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book has grown out of the research activities of the author in the fields of sound propagation in porous media and modelling of acoustic materials. It is assumed that the reader has a background of advanced calculus, including an introduction to differential equations, complex variables and matrix algebra. A prior exposure to theory of elasticity would be advantageous. Chapters 1-3 deal with sound propagation of plane waves in solids and fluids, and the topics of acoustic impedance and reflection coefficient are given a large emphasis. The topic of flow resistivity is presented in Chapter 2. Chapter 4 deals with sound propagation in porous materials having cylindrical pores. The topics of effective density, and of tortuosity, are presented. The thermal exchanges between the frame and the fluid, and the behaviour of the bulk modulus of the fluid, are described in this simple context. Chapter 5 is concerned with sound propagation in other porous materials, and the recent notions of characteristic dimensions, which describe thermal exchanges and the viscous forces at high frequencies, are introduced. In Chapter 6, the case of porous media having an elastic frame is considered in the context of Biot theory, where new topics described in Chapter 5 have been included.
Book Synopsis Computational Acoustics of Noise Propagation in Fluids - Finite and Boundary Element Methods by : Steffen Marburg
Download or read book Computational Acoustics of Noise Propagation in Fluids - Finite and Boundary Element Methods written by Steffen Marburg and published by Springer Science & Business Media. This book was released on 2008-02-27 with total page 584 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book provides a survey of numerical methods for acoustics, namely the finite element method (FEM) and the boundary element method (BEM). It is the first book summarizing FEM and BEM (and optimization) for acoustics. The book shows that both methods can be effectively used for many other cases, FEM even for open domains and BEM for closed ones. Emphasis of the book is put on numerical aspects and on treatment of the exterior problem in acoustics, i.e. noise radiation.
