Modes in exterior acoustics and determination of sound power
The numerical treatment of the acoustic exterior problem requires consideration of the Sommerfeld radiation condition, which means that all sound energy must scatter to infinity and no reflexions lead to radiation of sound from infinity back into the field. Conventional Finite Element Method (FEM) is limited to bounded domains with clear definable finite external boundaries. The Boundary Element Method (BEM) allows the calculation of the sound pressure field for unbounded domains with the limitation to degrees of freedom at the surface of the solid structures amid the surrounding fluid. To obtain system matrices and pressure field in the whole fluid, the Infinite Element Method (IFEM) is applied. Collaboration of FEM and IFEM in the fluid leads to a discrete system of linear equations comprising stiffness, damping and mass matrices that can be solved for the sound pressure field in the whole fluid, finally.
Although, acoustic modes are commonly associated to bounded domains, even modes in exterior acoustics can be found in the literature. On the one hand frequency-dependent acoustic radiation modes can be obtained as eigenvalues and corresponding right eigenvectors from the acoustic impedance matrix. On the other hand, normal modes are determined by a state space eigenvalue problem and do not depend on the frequency. The calculation of the radiated sound power by modal superposition gives correct results for normal as well as for radiation modes. This research project aims at development of techniques of identification of neglectable and significant modes and their contribution to the total superimposed sound power.
Interactive Acoustic Apps
For a lively and vivid lesson, whether in study, exercises, school or follow-up at home, the Chair of Vibroacoustics of Vehicles and Machines develops Acoustic Apps, which can be executed and controlled in the web browser on a PC, tablet computer or smartphone. With these apps, physical phenomena from the fields of acoustics, vibrations and mechanics can be simulated and visualized. The effort for the set up and the dismantling of experiments is omitted and through the use of digital media, the topics are taught differently and are provided to interested people and those who have problems to imagine the application of physics.
The physical problem are solved in the background on a server by using the finite element method (FEM) and the software COMSOL Multiphysics. The apps can be found here or in the navigation bar on the left hand side. Further links: the project description as a sponsored teaching concept of the TUM Lehrfonds, an article in the online magazine ExploreTUM, an article in the COMSOL blog and a blog article of the TU Munich at lehren.tum.de.
If you have questions or feedback, please contact Lennart Moheit or write an email to apps@vib.mw.tum.de.
Moheit, Lennart; Schmid, Johannes D.; Schmid, Jonas M.; Eser, Martin; Marburg, Steffen: Acoustics Apps: Interactive simulations for digital teaching and learning of acoustics. The Journal of the Acoustical Society of America 149 (2), 2021, 1175-1182 more…BibTeX
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2020
Kronowetter, Felix; Baydoun, Suhaib Koji; Eser, Martin; Moheit, Lennart; Marburg, Steffen: A Benchmark Study on Eigenfrequencies of Fluid-Loaded Structures. Journal of Theoretical and Computational Acoustics 28 (02), 2020, 2050013 more…BibTeX
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Kronowetter, Felix; Moheit, Lennart; Eser, Martin; Sepahvand, Kian K.; Marburg, Steffen: Spectral Stochastic Infinite Element Method in Vibroacoustics. Journal of Theoretical and Computational Acoustics 28 (02), 2020, 2050009 more…BibTeX
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Moheit, Lennart; Anthis, Spyridon; Heinz, Johannes; Kronowetter, Felix; Marburg, Steffen: Analysis of scattering by finite sonic crystals in free field with infinite elements and normal modes. Journal of Sound and Vibration 476, 2020, 115291 more…BibTeX
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2019
Eser, M.; Gurbuz, C.; Moheit, L.; Moosrainer, M.; Marburg, S.: Efficient Evaluation of Sound Radiation of an Electric Motor using Model Order Reduction. Proceedings of the 23rd International Congress on Acoustics, integrating 4th EAA Euroregio , DEGA, 2019Aachenmore…BibTeX
Eser, M.; Moheit, L.; Moosrainer, M.; Marburg, S.: Performante Simulation der Schallabstrahlung von Elektromotoren mittels Modellordnungsreduktion. Fortschritte der Akustik-DAGA : 45. Jahrestagung für Akustik, 18.-21. März, DEGA e.V., 2019 more…BibTeX
Kronowetter, F.; Moheit, L.; Sepahvand, K.; Marburg, S.: Spektral-stochastische Infinite-Elemente-Methode in der Vibroakustik. Fortschritte der Akustik - DAGA : 45. Jahrestagung für Akustik, 18.-21. März , DEGA e.V., 2019Rostockmore…BibTeX
Schmid, J. D.; Schmid, J. M.; Moheit, L.; Marburg, S.: Interaktive Akustik-Apps zur Veranschaulichung akustischer Phänomene in der Lehre. Fortschritte der Akustik-DAGA : 45. Jahrestagung für Akustik, 18.-21. März, DEGA e.V., 2019Rostockmore…BibTeX
Schmid, J. M.; Schmid, J. D.; Moheit, L.; Marburg, S.: Interaktive Akustik-App zur Visualisierung akustischer und strukturdynamischer Effekte an Musikinstrumenten. Fortschritte der Akustik-DAGA : 45. Jahrestagung für Akustik, 18.-21. März, DEGA e.V., 2019Rostockmore…BibTeX
Scholz, M.; Thomann, F.; Moheit, L.; T., Greß; W., Volk; S., Marburg: Jazz-Glocke: Sound Design, Strukturoptimierung und Guss. Fortschritte der Akustik-DAGA : 45. Jahrestagung für Akustik, 18.-21. März, DEGA e.V., 2019 more…BibTeX
2018
Herrnberger, Maximilian; Moheit, Lennart; Wagner, Philipp; Lohmann, Timo: Transferpfadanalyse auf Basis der Vierpolmethode bei Mehrquellenanregung in der Fahrzeugakustik. Fortschritte der Akustik - DAGA 2018 : 44. Jahrestagung für Akustik, 19. bis 22. März 2018 in München, DEGA e.V., 2018Münchenmore…BibTeX
L., Moheit; M., Maeder; S., Marburg: Interaktive Akustik-Apps - Akustik `klickbar' machen in Schule, Studium und Beruf. Fortschritte der Akustik - DAGA 2018 - 44. JAHRESTAGUNG FÜR AKUSTIK,19.-22. MäRZ 2018, DEGA e.V., 2018 more…BibTeX
L., Moheit; S., Marburg: Superposition frequenzunabhängiger Moden im akustischen Außenraum. Fortschritte der Akustik - DAGA 2018 - 44. JAHRESTAGUNG FÜR AKUSTIK,19.-22. MäRZ 2018, DEGA e.V., 2018 more…BibTeX
M., Scholz; L., Moheit; S., Marburg: Hand-Arm-Vibration: Review. Fortschritte der Akustik - DAGA 2018 - 44. JAHRESTAGUNG FÜR AKUSTIK,19.-22. MäRZ 2018, DEGA e.V., 2018 more…BibTeX
Moheit, Lennart; Marburg, Steffen: Superposition of frequency-independent normal modes in exterior acoustics. INTER-NOISE and NOISE-CON Congress and Conference Proceedings 257 (1), 2018, 608-616 more…BibTeX
Moheit, Lennart; Marburg, Steffen: Normal Modes and Modal Reduction in Exterior Acoustics. Journal of Theoretical and Computational Acoustics 26 (03), 2018, 1850029 more…BibTeX
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Moheit, Lennart; Marburg, Steffen: Superposition of frequency-independent normal modes in exterior acoustics. Proceedings of 6th conference Noise and vibration emerging methods, 2018 more…BibTeX
Moheit, Lennart; Marburg, Steffen: Superposition frequenzunabhängiger Moden im akustischen Außenraum. Fortschritte der Akustik - DAGA 2018 : 44. Jahrestagung für Akustik, 19. bis 22. März 2018 in München, DEGA e.V., 2018Münchenmore…BibTeX
Moheit, Lennart; Mäder, Marcus; Marburg, Steffen: Interaktive Akustik-Apps - Akustik `klickbar' machen in Schule, Studium und Beruf. Fortschritte der Akustik - DAGA 2018 : 44. Jahrestagung für Akustik, 19. bis 22. März 2018 in München, DEGA e.V., 2018Münchenmore…BibTeX
Scholz, Magdalena; Moheit, Lennart; Marburg, Steffen: Hand-Arm-Vibration: Review. Fortschritte der Akustik - DAGA 2018 : 44. Jahrestagung für Akustik, 19. bis 22. März 2018 in München, DEGA e.V., 2018Münchenmore…BibTeX
2017
Khosroshahi, Ferina Saati; Moheit, Lennart; Marburg, Steffen: Parameter variations for a porous layer simulation. The Journal of the Acoustical Society of America 141 (5), 2017, 4016 more…BibTeX
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Moheit, Lennart; Marburg, Steffen: Eigenwertproblem und modale Superposition im akustischen Außenraum. Fortschritte der Akustik - DAGA 2017 : 43. Jahrestagung für Akustik, 06. bis 09. März 2017 in Kiel, DEGA e.V., 2017 more…BibTeX
Moheit, Lennart; Marburg, Steffen: Acoustic radiation modes and normal modes in exterior acoustic problems. The Journal of the Acoustical Society of America 141 (5), 2017, 3978 more…BibTeX
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Moheit, Lennart; Marburg, Steffen: Infinite elements and their influence on normal and radiation modes in exterior acoustics. Journal of Computational Acoustics, 2017, 1650020 more…BibTeX
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Moheit, Lennart; Marburg, Steffen: Acoustic radiation modes and normal modes in unbounded domains. Proceedings of Meetings on Acoustics 30 (1), 2017, 022004 more…BibTeX
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Saati Khosroshahi, Ferina; Moheit, Lennart; Marburg, Steffen: Parameter variations for a porous layer simulation. Fortschritte der Akustik - DAGA 2017 : 43. Jahrestagung für Akustik, 06. bis 09. März 2017 in Kiel, DEGA e.V., 2017 more…BibTeX
Saati, Ferina; Moheit, Lennart; Marburg, Steffen: Parameter variations for a porous layer simulation. Proceedings of Meetings on Acoustics 30 (1), 2017, 030007 more…BibTeX
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2016
Moheit, L.; Marburg, S.: Konvergenz akustischer Außenraummoden mit infiniten Elementen. Fortschritte der Akustik - DAGA 2016 : 42. Jahrestagung für Akustik, 14. bis 17. März 2016 in Aachen, DEGA e.V, 2016 more…BibTeX
Moheit, L.; Marburg, S.: Convergence of modes in exterior acoustics problems with infinite elements. Proceedings of the 45th International Congress and Expositionon Noise Control Engineering, 201645th International Congress and Exposition on Noise Control Engineering: Towards a Quieter Future, INTER-NOISE 2016; Hamburg; Germany;more…BibTeX
2015
Moheit, L.; Marburg, S.: Vergleich frequenzabhängiger und - unabhägiger Moden der Schallabstrahlung akustischer Aussenraumprobleme. Fortschritte der Akustik, DEGA e.V, 2015 more…BibTeX
Moheit, L.; Peters, H.; Marburg, S.: A comparison of acoustic radiation modes and frequency-independent normal modes in acoustic exterior problems. Proceedings of NOVEM 2015, 2015 more…BibTeX
