Download or read book Transmission Line Matrix Modelling of Acoustic Waves with Applications to Active Noise Control in Exhausts and Ducts written by Fergus Cavanagh and published by . This book was released on 1994 with total page 181 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Transmission Line Matrix Modelling of Acoustic Waves with Application to Dynamic Boundary Problems written by Kieran Lynch and published by . This book was released on 1996 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Applied mechanics reviews written by and published by . This book was released on 1948 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Handbook of Noise and Vibration Control written by Malcolm J. Crocker and published by John Wiley & Sons. This book was released on 2007-10-05 with total page 1594 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two of the most acclaimed reference works in the area of acoustics in recent years have been our Encyclopedia of Acoustics, 4 Volume set and the Handbook of Acoustics spin-off. These works, edited by Malcolm Crocker, positioned Wiley as a major player in the acoustics reference market. With our recently published revision of Beranek & Ver's Noise and Vibration Control Engineering, Wiley is a highly respected name in the acoustics business. Crocker's new handbook covers an area of great importance to engineers and designers. Noise and vibration control is one largest areas of application of the acoustics topics covered in the successful encyclopedia and handbook. It is also an area that has been under-published in recent years. Crocker has positioned this reference to cover the gamut of topics while focusing more on the applications to industrial needs. In this way the book will become the best single source of need-to-know information for the professional markets.
Download or read book Modelling Room Acoustics Using Transmission Line Matrix Method written by Anirudh Prakhya and published by . This book was released on 2020-09-22 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: The primary objective of the project is to model room acoustics using Transmission Line Matrix Method (TLM). The method approximates acoustic wave propagation by Huygen's principle. It is best suited for equidistant nodes and fixed time steps coupled to the spatial distance of the nodes. The TLM method was applied to a one-dimensional (1-D) case of an air column. The results were validated using a model generated by Finite Difference Method (FDM). The results indicate no spurious peaks or built up errors. Accuracy of the plot could be made more fine by varying mesh size and propagation velocity while keeping time-step constant. In the two-dimensional (2-D) TLM model of a square plane considered on the surface of water, new issues were observed. The simulation creates dispersion effects. It was observed that this effect occurs when the wave pattern is sharp beyond a particular level. After making corrections, the TLM method was applied to other 2-D cases. In modelling moving sources, two methods were explored. The first implied the direct movement of the source by one node for some pre-defined number of time-steps i.e. moving source at some finite value of speed. The results indicate distortion in the radial propagation and sharp ends at the source. The second method requires dividing the intervening space into n sub-units and taking the corresponding weighted mean of the amplitudes at the two nodes. The obtained results were explained using Doppler effect. The TLM method was extended to model acoustic beam-steering using phased arrays. The applications of this are usually in radio communications. A rigid wall was used as the reflector. The pulses coming from each of the five sources were kept in a temporary store and at the next iteration, these values were used as the incident pulses. Thus superposing the effect of the five sources at each node in the grid. The beam can be propagated in a specific direction by varying the phase difference. The boundary conditions were varied and perfectly reflecting, perfectly absorbing and partially absorbing-partially reflecting boundaries were considered. The reflection coefficient values used at the boundaries are as follows: ρ = 1 for rigid walls, ρ = -1 for open ends and ρ = 0 for impedance boundaries. By varying the values of frequency, standing waves were generated in 1-D and 2-D cases. In 2-D waves were captured at the transition state. Three dimensional (3-D) room acoustics was simulated using TLM. Modelling in 3-D was lot more different from the rest as large computation time and computational power was required. There are numerous methods available to model 3-D case like triangular meshing, Cartesian meshing, tetrahedral meshing etc. Cartesian method was used for this project as it is the natural extension of 2-D TLM code. The wave propagation was captured on three perpendicular planes parallel to the coordinate planes. Open, rigid and impedance boundaries were also modelled. The results were found to be satisfactory. From the results obtained, it can be concluded that TLM is equivalent to FDM in terms of its usefulness. Despite the computational time and power being higher than FDM, the results are more accurate and the simulation itself runs without any hindrances. Compared to the problems of instability or very high noise, that are frequently encountered in FDM, TLM stands as the better solution.
Download or read book The Active Noise Control of a One dimensional Duct written by Young-Su Lee and published by . This book was released on 1997 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Modal Concept for Active Noise Control in Circular Or Annular Ducts written by Ulf Tapken and published by . This book was released on 2001 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Active control of sound propagation in ducts plays an important role in many technical applications e.g. the attenuation of noise in ventilating system or in the exhaust system of combustion engines. Today many control strategies exist for the simplest case, which is the noise control in the low frequency range in ducts the lateral dimensions of which are small compared to wavelength of sound. Up to the cut-on frequency of the first higher order mode a suppression of the propagating plane sound waves is possible in a broad frequency range. The situation is more difficult when the lateral duct dimensions become large compared to the wavelength as for example in the intake section of an aircraft engine With increasing rotor speed an increasing number of acoustical modes becomes present. This means. the system comprises all increasing number of degrees of freedom. As a consequence. control of the sound field is practicable just in a narrow frequency band or even limited to discrete frequencies.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 892 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Noise Controlling Casings written by Marek Pawelczyk and published by CRC Press. This book was released on 2022-07-28 with total page 279 pages. Available in PDF, EPUB and Kindle. Book excerpt: Noise-Controlling Casings offers a range of feasible noise-controlling strategies for different kinds of devices generating excessive noise. Depending on the required performance and the availability of energy sources, three solution categories are presented: passive (no external energy is needed, but performance is limited), semi-active (little energy is needed, but performance achieves higher values) and active (best performance, but an external energy source is needed). Two very important benefits of these proposed solutions are global noise reduction (in an entire enclosure or the surrounding space) and compact technology (contrary to other active noise control solutions requiring a large number of secondary sources and distributed sensors). Many of the solutions presented are original approaches by the authors, their own developed concepts and new elements and designs that have gained recognition in prestigious journals. The book provides a theoretical background to the research, looking at system configurations, mathematical modelling, signal processing implementation and numerical analysis. The proposed ideas can be applied to any devices provided they have casings of thin walls or they can be enclosed by casings of thin walls. Applications include industrial devices, household appliances, vehicle or aircraft cabins and more. This book will be of interest to professionals and students in the fields of acoustics, vibration, signal processing, control, automotive and aircraft engineering.
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1999 with total page 974 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Global Active Noise Control of a One dimensional Acoustic Duct Using a Feedback Controller written by Andrew James Hull and published by . This book was released on 1990 with total page 224 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Active Control of Fan Noise written by National Aeronautics and Space Adm Nasa and published by . This book was released on 2018-10-22 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: A computational method to predict modal reflection coefficients in cylindrical ducts has been developed based on the work of Homicz, Lordi, and Rehm, which uses the Wiener-Hopf method to account for the boundary conditions at the termination of a thin cylindrical pipe. The purpose of this study is to develop a computational routine to predict the reflection coefficients of higher order acoustic modes impinging on the unflanged termination of a cylindrical duct. This effort was conducted wider Task Order 5 of the NASA Lewis LET Program, Active Noise Control of aircraft Engines: Feasibility Study, and will be used as part of the development of an integrated source noise, acoustic propagation, ANC actuator coupling, and control system algorithm simulation. The reflection coefficient prediction will be incorporated into an existing cylindrical duct modal analysis to account for the reflection of modes from the duct termination. This will provide a more accurate, rapid computation design tool for evaluating the effect of reflected waves on active noise control systems mounted in the duct, as well as providing a tool for the design of acoustic treatment in inlet ducts. As an active noise control system design tool, the method can be used preliminary to more accurate but more numerically intensive acoustic propagation models such as finite element methods. The resulting computer program has been shown to give reasonable results, some examples of which are presented. Reliable data to use for comparison is scarce, so complete checkout is difficult, and further checkout is needed over a wider range of system parameters. In future efforts the method will be adapted as a subroutine to the GEAE segmented cylindrical duct modal analysis program. Kraft, R. E. Unspecified Center NAS3-26617; RTOP 538-03-11...
Download or read book Active Control of Fan Noise written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-30 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: A computational method to predict modal reflection coefficients in cylindrical ducts has been developed based on the work of Homicz, Lordi, and Rehm, which uses the Wiener-Hopf method to account for the boundary conditions at the termination of a thin cylindrical pipe. The purpose of this study is to develop a computational routine to predict the reflection coefficients of higher order acoustic modes impinging on the unflanged termination of a cylindrical duct. This effort was conducted wider Task Order 5 of the NASA Lewis LET Program, Active Noise Control of aircraft Engines: Feasibility Study, and will be used as part of the development of an integrated source noise, acoustic propagation, ANC actuator coupling, and control system algorithm simulation. The reflection coefficient prediction will be incorporated into an existing cylindrical duct modal analysis to account for the reflection of modes from the duct termination. This will provide a more accurate, rapid computation design tool for evaluating the effect of reflected waves on active noise control systems mounted in the duct, as well as providing a tool for the design of acoustic treatment in inlet ducts. As an active noise control system design tool, the method can be used preliminary to more accurate but more numerically intensive acoustic propagation models such as finite element methods. The resulting computer program has been shown to give reasonable results, some examples of which are presented. Reliable data to use for comparison is scarce, so complete checkout is difficult, and further checkout is needed over a wider range of system parameters. In future efforts the method will be adapted as a subroutine to the GEAE segmented cylindrical duct modal analysis program. Kraft, R. E. Unspecified Center NAS3-26617; RTOP 538-03-11...
Download or read book Transmission Line Matrix Modelling of Acoustic Devices written by Michael Simms and published by . This book was released on 1997 with total page 153 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Transmission Line Matrix TLM in Computational Mechanics written by Donard de Cogan and published by CRC Press. This book was released on 2005-11-01 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt: The finite element method reigns as the dominant technique for modeling mechanical systems. Originally developed to model electromagnetic systems, the Transmission Line Matrix (TLM) method proves to match, and in some cases exceed, the effectiveness of finite elements for modeling several types of physical systems. Transmission Line Matrix in Computational Mechanics provides a tutorial approach to applying TLM for modeling mechanical and other physical systems. Transmission Line Matrix in Computational Mechanics begins with the history of TLM, an introduction to the theory using mechanical engineering concepts, and the electromagnetic basics of TLM. The authors then demonstrate the theory for use in acoustic propagation, along with examples of MATLAB® code. The remainder of the book explores the application of TLM to problems in mechanics, specifically heat and mass transfer, elastic solids, simple deformation models, hydraulic systems, and computational fluid dynamics. A discussion of state-of-the-art techniques concludes the book, offering a look at the current research undertaken by the authors and other leading experts to overcome the limitations of TLM in applying the method to diverse types of systems. This valuable reference introduces students, engineers, and researchers to a powerful, accurate, and stable alternative to finite elements, providing case studies and examples to reinforce the concepts and illustrate the applications.
Download or read book Structural Acoustic Prediction and Interior Noise Control Technology written by and published by DIANE Publishing. This book was released on 2001 with total page 70 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Phase mode Transformation Matrix Application for Transmission Line and Electromagnetic Transient Analyses written by Afonso José do Prado and published by . This book was released on 2011 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Frequency-dependent transmission line models can be developed in phase domain or in mode domain. Associated to these transmission line models, time domain or frequency domain can be used for electromagnetic transient analysis solutions. Because of these options, there are several models for transmission line representation in electromagnetic transient studies. One reason for this is the longitudinal parameter frequency dependence. This book presents a variety of models which serve to improve the frequency dependence representation. In some cases, phase-mode transformation is applied, considering the problem in mode domain, and searching for improving the frequency-dependent parameter representation. On the other hand, changes in the system structure as well as voltage and current surge waves are better modelled on the time domain.
