Optimal Soundfield Generation for Sound Reinforcement in Time and Frequency Domain

• Applicants: Dr.-Ing. Mathias Lemke; Professor Dr. Stefan Weinzierl
• Subject Area: Acoustics ; Fluid Mechanics
• Term: from 2018 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 393106680

• Final Report Year: 2024

Final Report Abstract

Today, large-scale sound reinforcement systems for speech and music are usually realized with loudspeaker array systems, which have to be optimized regarding different degrees of freedom (distribution/geometry/housing design of the drivers) and different boundary conditions (geometry of the auditorium and the areas to be avoided, available acoustic power) concerning an optimal control of the array. This is an ill-posed inverse problem in the mathematical sense, where the number of sources is always significantly smaller than the number of receivers. In this project, a new access to the solution to this problem was developed by (a) further developing traditional approaches for the optimization of the radiation of array systems in the frequency domain by a multi-objective-goal-attainment approach and (b) implementing for the first time an optimization in the time domain with the adjoint-based method, which has proven successful in analogous problems in fluid mechanics. Thus, for the first time, the influence of a base flow on the generated sound field can be taken into account, which can be of great practical relevance - for example, when wind influences the speech intelligibility in stadiums. While a theorybased presetting of the geometric driver arrangement (Polygonal Audience Line Curving, PALC) was developed for traditional optimization in the frequency domain, the adjoint-based method has proven to be suitable for finding both suitable positions and driver functions of the loudspeakers for a target sound field. Not only the directional characteristics of the drivers, which are often complex in practice, can be modeled precisely, but also base flows can be taken into account. While the influence of the room was initially only taken into account for rigid boundary conditions, impedance-boundary conditions are also to be modeled and optimized in a follow-up project, so it will not only be possible to optimize the sound sources in the room but also the room acoustic conditions themselves.

Publications

• An Analytical Approach for Optimizing the Curving of Line Source Arrays. Journal of the Audio Engineering Society, 66(1/2), 4-20.
  Straube, Florian; Schultz, Frank; Bonillo, David & Weinzerl, Stefan
  
• Adjoint-based optimization of sound reinforcement including non-uniform flow. The Journal of the Acoustical Society of America, 146(3), 1774-1785.
  Stein, Lewin; Straube, Florian; Sesterhenn, Jörn; Weinzierl, Stefan & Lemke, Mathias
  
• Adjoint-based sound reinforcement in the time domain. In Proceedings of the 23rd International Congress on Acoustics, 2019.
  L. Stein; F. Straube; J. Sesterhenn; S. Weinzierl & M. Lemke
  
• Adjoint-Based Identification of Sound Sources for Sound Reinforcement and Source Localization. Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 263-278. Springer International Publishing.
  Lemke, Mathias & Stein, Lewin
  
• Directional sound source modeling using the adjoint Euler equations in a finite-difference time-domain approach. The Journal of the Acoustical Society of America, 148(5), 3075-3085.
  Stein, Lewin; Straube, Florian; Weinzierl, Stefan & Lemke, Mathias
  
• Synthese komplexer Richtcharakteristiken fur eine Schallfeldoptimierung im Zeitbereich. In Fortschritte der Akustik - DAGA 2020, pages 1192–1195, 2020.
  M. Lemke; L. Stein; A. Holter; F. Straube & S. Weinzierl
  
• Adjungierten-basierte Schallfelderzeugung im Zeitbereich mit Zielfunktion im Frequenzraum. In Fortschritte der Akustik - DAGA 2021, pages 1633–1636
  P. Seeler, A. Holter, S. Weinzierl & M. Lemke
  
• Adjungierten-basierte Synthese und Bestimmung optimaler Treiberfunktionen von Lautsprechern mit komplexer Richtcharakteristik. In Fortschritte der Akustik - DAGA 2021, pages 1629–1632
  M. Lemke, L. Stein, A. Holter & S. Weinzierl
  
• Enhanced polygonal audience line curving for line source arrays. In Audio Engineering Society Convention 150, May 2021.
  A. Holter; F. Straube; F. Schultz & S. Weinzierl
  
• External acoustic control of the laminar vortex shedding past a bluff body. Fluid Dynamics Research, 53(1), 015506.
  Lemke, Mathias; Citro, Vincenzo & Giannetti, Flavio
  
• SPL-basierte Optimierung der Krummung von Line-Source-Arrays mit PALC. Technical report, Technische Universitat Berlin
  A. Holter, F. Schultz, F. Straube & S. Weinzierl
  
• Supervised learning for multi zone sound field reproduction under harsh environmental conditions, 2021.
  H. Sallandt; P. Krah & M. Lemke
  
• Adjoint-based analyzes in acoustic time-domain simulations. In Proceedings of the 24th International Congress on Acoustics, 2022.
  M. Lemke
  
• Adjungierten-basierte Optimierung von Impedanz-Randbedingungen im Zeitbereich. In Fortschritte der Akustik - DAGA 2022, pages 907–910, 2022.
  J. Reiss & M. Lemke
  
• Analysis and comparison of FDTD discretization procedures for room acoustical simulations. In Fortschritte der Akustik - DAGA 2022, pages 903–906
  A. Holter, M. Lemke & S. Weinzierl
  
• Adjungierten-basierte Optimierung von akustischen Berandungen im Zeitbereich mittels Volumenpenalisierung. In Fortschritte der Akustik - DAGA 2023, pages 1070–1073
  A. Holter, E. Porcinai, M. Lemke & S. Weinzierl
  
• Approximate acoustic boundary conditions in the time-domain using volume penalization. The Journal of the Acoustical Society of America, 153(2), 1219-1228.
  Lemke, Mathias & Reiss, Julius
  
• Physics-informed interpolation of directional characteristics of sound sources. In Forum Acusticum 2023, 2023.
  M. Lemke; A. Holter; D. Ackermann & S. Weinzierl
  
• Physikalisch informierte Interpolation von Richtcharakteristiken. In Fortschritte der Akustik - DAGA 2023, pages 1656–1659
  M. Lemke, A. Holter, D. Ackermann & S. Weinzierl