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A study case applying a method to retrieve complex surface impedances from statistical absorption coefficients aiming room acoustics simulation using boundary element method 49

A study case applying a method to retrieve complex surface i...

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49th International Congress and Exposition on Noise Control engineering, INTER-NOISE 2020

作者： Soares, Murilo C. Brandão, Eric Tenenbaum, Roberto A. Alvim, Luiz Augusto T.F. Acoustical Engineering Civil Engineering Graduate Program Roraima Av. 1000 Santa Maria RS Brazil Acoustical Engineering Roraima Av. 1000 Santa Maria RS Brazil

ISBN: (纸本)9788994021362

A common way to provide material data for room acoustics simulation is by means of octave-band random-incidence absorption coefficients. This paper investigates a technique to transform real-valued absorption coefficients into complex surface impedances, which are needed in wave-based methods. This technique was first presented by Mondet in 2020 and is based on the solution of a constrained optimization problem. Room acoustic simulations are performed in the low frequency bands using bempp. This is an open source boundary element method library invoked from Python scripts. Two rooms are considered as theoretical test cases. First, simulations are performed using surface impedances obtained from known material models. Transfer functions for some source-receiver configurations are computed and taken as reference. In a second step, absorption coefficients are calculated from these surface impedances. Then, two different approaches are used to retrieve the surface impedances. In the direct approach, real valued surface impedances are calculated from the absorption data. In the indirect approach, the constrained optimization is used to estimate the complex valued surface impedances. Those, in turn, are prescribed as boundary conditions to the simulated rooms. Individual source-receiver transfer functions are compared and the modal assurance criterion for both rooms is also calculated. © Proceedings of 2020 International Congress on Noise Control engineering, INTER-NOISE 2020. All rights reserved.

关键词： Boundary element method

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Optimization of Acoustic Porous Material Absorbers Modeled as Rigid Multiple Microducts Networks: Metamaterial Design Using Additive Manufacturing

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SSRN 2024年

作者： Mareze, Paulo Henrique Silva, Olavo M. Fonseca, William D'Andrea Brandão, Eric Brandão Godinho, Luis Manuel Cortesão Acoustical Engineering Program Federal University of Santa Maria Roraima Av. 1000 Camobi RS Santa Maria Brazil Graduate Program in Mechanical Engineering Federal University of Santa Maria Roraima Av. 1000 Camobi RS Santa Maria Brazil Graduate Program in Architecture Urbanism and Landscaping Federal University of Santa Maria Roraima Av. 1000 Camobi RS Santa Maria Brazil Graduate Program in Civil Engineering Federal University of Santa Maria Roraima Av. 1000 Camobi RS Santa Maria Brazil Vibration and Acoustics Laboratory Federal University of Santa Catarina Campus Universitário Florianópolis SC Trindade Brazil ISISE Department of Civil Engineering University of Coimbra Coimbra Portugal

This research presents an advanced approach to enhancing sound absorption in porous acoustic metamaterials through the optimization of a micro-duct network. The study employs a combination of analytical and numerical methods, systematically adjusting micro-duct diameters within a 2D grid to optimize absorption coefficients at specific frequency bands. The Finite Element Transfer Method (FETM) is utilized for modeling, supported by a multi-objective function influenced by the surface impedance of the network. This approach ensures practical applicability and manufacturability of the designed metamaterial. A significant aspect of the study is the development of an analytical mobility matrix for each micro-duct, integrated through the Transfer Matrix Method with visco-thermal dissipation theory. This integration results in a physically coherent model. The optimization employs the Method of Moving Asymptotes (MMA), effectively managing the complexity associated with a large number of design variables. Subsequently, the optimized structure is adapted into a 3D grid, facilitating prototype creation using Additive Manufacturing Technology (AMT) with a specific polymer material. The research methodology is validated through four distinct test cases, each demonstrating the efficacy and adaptability of the optimization tools and techniques. Experimental validation, conducted using an impedance tube, indicates a significant shift in the first absorption maximum from 2500 Hz to 1000 Hz, achieved without altering the material thickness. Additional validation through 3D Finite Element Method (FEM) modeling, which includes viscothermal effects, further confirms the acoustic efficiency of the final designs. While the potential for achieving lower sub-wavelength conditions is recognized, the study opts for simpler structures, considering the current limitations of 3D printing technology. This study contributes to both theoretical understanding and practical application in acoustic m

关键词： Ducts

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Influence of edge diffraction on the in situ measurement of impedance using microphone arrays 49

Influence of edge diffraction on the in situ measurement of ...

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49th International Congress and Exposition on Noise Control engineering, INTER-NOISE 2020

作者： Brandão, Eric Fernandez-Grande, Efren Acoustical Engineering and Civil Engineering Graduate Program Roraima avenue 1000 Santa Maria - RS Brazil Ørsteds Plads Building 352 Kgs. Lyngby2800 Denmark

ISBN: (纸本)9788994021362

When measuring the surface impedance and/or the sound absorption coefficient of a material sample in situ, one of the main concerns is the sample size effect due to edge diffraction. In recent years, several in situ impedance measurement techniques using arrays of microphones have been proposed. This paper aims at analysing the the effect of edge diffraction on the in situ measurement with arrays of microphones based on a numerical simulation framework. A simplified Boundary Element Method (BEM) is used to emulate the measurement performed by two types of arrays: (i) - a double layer array, consisting of two parallel layers of uniformly spaced microphones;(ii) - a three-dimensional randomized array, consisting of an irregular distribution of measurement points within a parallelepiped. The study examines different array configurations (size and number of sensors) and sample properties (size and absorption). The wave-number spectrum is used to examine the effect of edge diffraction. The influence of edges on the estimation of surface impedance and the absorption coefficient is also analysed and compared to the estimation made with a single pressure-velocity probe. © Proceedings of 2020 International Congress on Noise Control engineering, INTER-NOISE 2020. All rights reserved.

关键词： Microphones

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Estimation of the effective perceived noise level during approach of the AMX A-1 military aircraft 170

Estimation of the effective perceived noise level during app...

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170th Meeting of the acoustical Society of America 2015

作者： Murta, Bernardo H. Greco, Gil F. Bernardi, Jean C. Pereira, Matheus Paul, Stephan Undergraduate Program of Acoustical Engineering Federal University of Santa Maria Santa Maria Brazil Laboratory of Vibrations and Acoustics Universidade Federal de Santa Catarina Florianopolis Brazil

Aircraft noise is an important cause of annoyance mainly in regions close to airports or military airbases. Civil aircraft data of sound emission, such as Effictive Perceived Noise Level (EPNL), are commonly available to the public however for military aircrafts such data is not easily accessible. Noise emission is commonly quantified in terms of Effective Perceived Noise Level during approach, low altitude overflight and simulated take-off. This study presents the results of the estimation of the EPNL for the AMX-A1 aircraft during approach at Santa Marias Airbase, in south Brazil. Since there is an University and its Hospital on the surroundings of the airbase, the approach is the most annoying situation. The measurements were made at the vicinities of the airbase based on the equivalent procedures established by ICAO where calibrated wav signals were recorded and processed leading to results of EPNL of the order of 140 EPNdB. The calculated levels were found to be coherent for military aircrafts and shall be validated with further investigation. © 2016 acoustical Society of America.

关键词： Acoustic noise

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Estimation of the effective perceived noise level during approach of the AMX A-1 military aircraft

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Proceedings of Meetings on Acoustics 2015年第1期25卷

作者： Bernardo H. Murta Gil F. Greco Jean C. Bernardi Matheus Pereira Stephan Paul 1Undergraduate Program of Acoustical Engineering Federal University of Santa Maria Santa Maria Brazil be.murta@*** gil.greco@eac.ufsm.br jean.c.bernardi@*** matheus.pereira@eac.ufsm.br 2Laboratory of Vibrations and Acoustics Universidade Federal de Santa Catarina Florianopolis Brazil stephan.paul.acoustic@***

Aircraft noise is an important cause of annoyance mainly in regions close to airports or military airbases. Civil aircraft data of sound emission, such as Effictive Perceived Noise Level (EPNL), are commonly available to the public however for military aircrafts such data is not easily accessible. Noise emission is commonly quantified in terms of Effective Perceived Noise Level during approach, low altitude overflight and simulated take-off. This study presents the results of the estimation of the EPNL for the AMX-A1 aircraft during approach at Santa Maria's Airbase, in south Brazil. Since there is an University and it's Hospital on the surroundings of the airbase, the approach is the most annoying situation. The measurements were made at the vicinities of the airbase based on the equivalent procedures established by ICAO where calibrated wav signals were recorded and processed leading to results of EPNL of the order of 140 EPNdB. The calculated levels were found to be coherent for military aircrafts and shall be validated with further investigation.

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Interplay of noise and non noise aspects in the quality of life of an airbase neighborhood

Interplay of noise and non noise aspects in the quality of l...

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41st International Congress and Exposition on Noise Control engineering 2012, INTER-NOISE 2012

作者： Barbosa, Anallu Rosa Paul, Stephan Postgraduate Program in Civil Engineering Now at Department of Architecture and Urbanism Universidade Federal de Santa Maria Santa-Maria Rio Grande do Sul 97105-900 Brazil Department of Acoustical Engineering Universidade Federal de Santa Maria Santa-Maria Rio Grande do Sul 97105-900 Brazil

ISBN: (纸本)9781627485609

In Brazil, studies to quantify the annoyance caused by aircraft noise on people living around airports and airbases are still incipient. Current operations on Santa Maria airbase and an expected expansion of the passenger operations and consequently an increase of noise emission, were determining factors for the development of this research. In the first part of the study a qualitative study was carried out featuring semi-structured interviews with 15 individuals from military personnel and their families living in next to the airbase and 15 civilians living in the neighborhood near the runway. We collected information regarding various aspects, such as interference of aircraft noise in daily life, general effects of aircraft noise and individual attitudes against exposure to aircraft noise. The qualitative data obtained were analysed using the Grounded Theory, resulting in a conceptual model that shows the relationship between military aircraft noise, the context of the neighborhood and satisfaction with other aspects than aircraft noise.

关键词： Noise pollution

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The international noise awareness day in Brazil -its development, guidelines and key actions

The international noise awareness day in Brazil -its develop...

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18th International Congress on Sound and Vibration 2011, ICSV 2011

作者： Paul, Stephan Kuniyoshi, Isabel Undergraduate Program in Acoustical Engineering Universidade Federal de Santa Maria 97105-900 Santa Maria Brazil Faculdade S˜ao Lucas Porto Velho-RO Brazil

ISBN: (纸本)9781618392596

Noise pollution is a considerable problem affecting negativly the quality of life of a large portion of people worldwide. For many noise problems technical solutions have been developed over the time and are ready to be implemented. Additionally proper education on noise is known to avoid or at least reduce environmental problems. Noise awareness campaigns can help to match the aim of reducing noise pollution and to increase quality of people affected by noise in many ways. One of such campaigns is the International Noise Awareness Day, celebrated every year in april. While the campaign exists internationally for 15 years now it has begun only in 2008 in Brazil, with the aid of the Brazilian Society of Acoustics SOBRAC and the Brazilian Academy of Audiology ABA. The campaign is orientated by the guidelines of the Center for the Hard of Hearing and the actions developed by the German "Tag gegen den Läarm", which is organized by the German acoustical Society. The present article will review the development of the campaign in Brazil, the guiding principles of the Brazilian campaign, its modifications according to possibilities and necessities in Brazil, and some key actions developed within the last years. Copyright © (2011) by the International Institute of Acoustics & Vibration.

关键词： Noise pollution

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Application of high temperature superconducting wire to magnetostrictive transducers for underwater sonar

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NAVAL ENGINEERS JOURNAL 1997年第1期109卷 31-39页

作者： Joshi, CH Lindberg, JF Clark, AE Dr. Chad H. Joshi:is president of Energen Incorporated an engineering and development firm specializing in cryogenic and electromechanical systems. The research presented here was conducted while he was employed at American Superconductor Coporation where he held both technical and program management positions. While there Dr. Joshi managed the development of several demonstration products including the sonar transducer presented here. He holds M.S. and Sc.D. degreesfrom the Massachusetts Institute of Technology and a B.S. degree from the Worcester Polytechnic Institute. He has worked in several diverse fields including solar energy fluidized bed technology and superconductivity. His work on stochastic analysis of solar insolation was recognized by the ASME and his doctoral research was accorded international recognition for its unique contribution to understanding quenching in superconducting magnets. Dr. Joshi has numerous patents and more than thirty-five technical publications to his credit. He is a registered Professional Engineer in Massachusetts and an active member of ASME and IEEE. He is a co-founder and treasurer of the New England Chapter of the Cryogenics Society of America. He will be listed in Whos Who in the East in 1997. Jan Lindberg:is a physicist in the Transducers and Arrays Division of the Naval Undersea Warfare Center in New London Connecticut. He leads NUWC'S exploratory development efforts for transduction science and currently is spearheading an effort to introduce high-energy density active materials into tactical sonar systems. With the discovery of high temperature superconductivity he saw the potential benefit of integrating several emerging technologies and enticed American Superconductor Corp. to develop a high temperature superconducting transducer which resulted in the March 1993 demonstration of the world's first integrated high temperature superconducting device. Mr. Lindberg's current interests involve design of high power ultrasonic copolymer arrays characterization of

A low-frequency underwater acoustic transducer integrating high-temperature superconducting (HTS) coils and terbium-dysprosium (TbDy) magnetostrictive material was designed, fabricated and tested. This represents a novel application for high-temperature superconductivity and is a first example of an integrated system involving HTS coils cooled by a mechanical cryocooler. It also brings HTS technology together with a novel magnetic materials technology. The I-ITS coils were fabricated using react-and-wind BiSrCaCuO-2223 HTS wires. They produce a peak field of 0.1 Tesla at 50 K. A single-stage, Stirling-cycle cryocooler was used to cool the coils and the TbDy driver to cryogenic temperatures (50-65K). The coils provide an AC magnetic field superimposed on a DC bias field, which produces oscillatory strain within the magnetostrictive rod;this motion is transmitted through a cryostat to two head masses which project sound into the surrounding environment. High power acoustic output can be obtained by operating the transducer at its resonance frequencies of 520 Hz in air and 430 Hz underwater. This development demonstrates that, unlike low temperature superconductors, HTS wires can be considered for AC applications due to the low losses in these superconductors and the higher heat capacities of materials at temperatures above liquid helium.

关键词： Underwater equipment

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DAMAGE CONTROL - THE LAST LINE OF SHIPBOARD DEFENSE

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NAVAL ENGINEERS JOURNAL 1992年第1期104卷 63-79页

作者： HERMAN, S LOESER, CT Stanley Hermanis the acting director of the Ship Survivability Subgroup (Sea 55X) at the Naval Sea Systems Command. He received a BSME from Northeastern University in 1966 and a MSME from Northeastern in 1970. In 1978 he completed requirements for a Certificate in Acoustics at Catholic University and in 1989 he completed the Program Management Course at the Department of Defense Systems Management College. He is a registered professional engineer in Washington D.C. a certified NavSea Material Professional and a member of ASME ASE and SNAME. Mr. Herman began his career with the Navy Department immediately after high school working as a student trainee (marine engineer) at the Boston Naval Shipyard until 1966. Upon obtaining his BSME he served as a project engineer in the Noise Shock and Vibration Group at the Boston Naval Shipyard and was responsible for conducting and directing shipyard and at-sea testing and evaluation of components systems and structure for surface combatant and auxiliary naval craft. In 1974 he transferred to the Naval Sea Systems Command where he was the coordinator of survivability and detection for the SSBN Trident submarine acquisition project manager PMS 396. He was responsible for directing efforts to enhance the acoustical silencing underwater explosion shock protection and shipboard vibration control for this latest class of strategic missile submarines. From 1982 to 1986 Mr. Herman was assigned as head of the Submarine Protection branch Sea 55X11 where he was responsible for directing submarine shock hardening programs. From 1986 to 1991 he served as division director for damage control Systems Safety Personnel Protection and CBR Defense Sea 55X2. In 1991 he assumed his present position of acting director Ship Survivability Subgroup Sea 55X. Christopher T. Loeseris currently acting director of the Damage Control and Ship Design Systems Safety Division at the Naval Sea Systems Command. The division is responsible for lifecycle management of damage control chemical

This paper addresses the ship, system and equipment design features, operational doctrine and training that has been developed to provide effective shipboard damage control. Both the ship and the sailor are addressed, since both are integral and interdependent components of the damage control "system." Also, the enhancements afforded to protection of personnel from the effects of conventional and nonconventional weapons are discussed. Finally, a brief look into the future is presented. With the shrinking defense budget and corresponding reduction in fleet size and ship manning, novel system designs and automated decision aids will be required to do the job.

关键词： Naval Vessels

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BANQUET ADDRESS - TECHNOLOGY IS FUN, ITS THE OTHER THINGS

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NAVAL ENGINEERS JOURNAL 1981年第3期93卷 57-59页

作者： FROSCH, RA President American Association of Engineering Societies Inc Dr. Robert A. Frosch born in New York City on 22 May 1928 attended Columbia University from which he received his B.A. degree in 1947 his M.A. degree in 1949 and his Ph.D. degree in 1952 all in the field of Theoretical Physics. While completing his studies for his doctorate he joined Columbia's Hudson Laboratories in 1951 and worked on naval research projects as a Research Scientist until 1958 when he became the Director Hudson Laboratories a post he held until 1963. From 1965 to 1966 he was Deputy Director Advanced Research Projects Agency (APRA) Department of Defense (DOD) having first joined ARPA in 1963 as the Director for Nuclear Test Detection the position he held until 1965. Since 1969 he also has served as the DOD member of the Committee for Policy Review National Council of Marine Resources and Engineering Development and in 1967 and 1970 as the Chairman of the U.S. Delegation to the Intergovernmental Oceanographic Commission meetings at UNESCO in Paris. In addition he was the Assistant Secretary of the Navy for Research & Development from 1966 to 1973 Assistant Executive Director of the United Nations Environment Program with the rank of Assistant Secretary General of the United Nations from 1973 to 1975 and Assistant Director for Applied Oceanography at the Woods Hole Oceanographic Institution from 1975 until mid-1977. In June 1977 he became the Administrator of the National Aeronautics and Space Agency (NASA) the position he held prior to joining the American Association of Engineering Societies (AAES) Incorporated. On 20 January 1981 he was elected to his present post as President AAES. Additionally he was the Sea Grant Lecturer for the Massachusetts Institute of Technology in 1974 and currently is a National Lecturer for Sigma Xi. During his distinguished career Dr. Frosch has been the recipient of numerous awards among which are the Arthur S. Flemming Award in 1966 the Navy Distinguished Public Service Award in 1

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