The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
Aalto

Room Acoustics Modeling with the Digital Waveguide Mesh – Boundary Structures and Approximation Methods

Antti Kelloniemi

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Electrical and Communications Engineering for public examination and debate in Auditorium S4 at Helsinki University of Technology (Espoo, Finland) on the 24th of November, 2006, at 12 o'clock noon.

Overview in PDF format (ISBN 951-22-8451-0)   [570 KB]
Dissertation is also available in print (ISBN 951-22-8450-2)

Abstract

The goal of this research was to develop realistic and efficient simulation models and approximation methods for sound wave propagation in rooms and other closed spaces. The focus was on optimization of boundary structures and on the use of models with high or low dimensionality in the simulation of three-dimensional wave propagation.

Modeling of wave phenomena such as diffusion and interference is needed for precise physical simulations of architectural acoustics. Approximation of sound propagation by geometrical methods is not sufficient in spaces with small dimensions or complicated shapes, and at low frequencies. The digital waveguide mesh method studied in this thesis research includes these phenomena automatically.

In this work, improvement of boundary model accuracy was pursued. Reflection coefficient values were modeled using novel equations relating the input and output signals at the mesh junctions. First, constant real-valued reflection coefficients were implemented with special attention to the absorbing boundary condition. Then, a more flexible solution was introduced, offering the possibility of directional dependency of the reflection coefficient. The last boundary structure proposed in this work makes it possible to define the boundary characteristics in a frequency-dependent manner.

In addition to the boundary methods, new ways of approximating the reverberation characteristics of a space have been addressed. As a full three-dimensional mesh is too demanding of computer resources and an unnecessarily exact simulation method for many uses, a computationally lighter solution using multiple two-dimensional meshes was introduced. Its benefits in spatial wave propagation modeling and visualization are discussed. Also, the concept of hyperdimensional meshes is exploited to show that small sized "hypermeshes" can be used as efficient models of high-frequency reverberation.

The novel techniques proposed in this research improve the accuracy and efficiency of the digital waveguide mesh models. These techniques are expected to be used in simulations of room acoustics and musical instruments, as well as in visualizations of wave propagation and in the creation of artificial reverberation effects.

This thesis consists of an overview and of the following 8 publications:

  1. A. Kelloniemi, D. T. Murphy, L. Savioja, and V. Välimäki. Boundary Conditions in a Multi-Dimensional Digital Waveguide Mesh. In Proceedings of the 29th IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP 2004), Vol. 4, pp. 25-28, Montreal, Canada, May 2004. © 2004 IEEE. By permission.
  2. A. Kelloniemi, L. Savioja, and V. Välimäki. Spatial Filter-Based Absorbing Boundary for the 2-D Digital Waveguide Mesh. IEEE Signal Processing Letters, Vol. 12, Issue 2, pp. 126-129, February 2005. © 2005 IEEE. By permission.
  3. A. Kelloniemi. Improved Adjustable Boundary Condition for the 2-D Digital Waveguide Mesh. In Proceedings of the 8th International Conference on Digital Audio Effects (DAFx-05), pp. 237-242, Madrid, Spain, September 2005. © 2005 by author.
  4. A. Kelloniemi. Improved Adjustable Boundary Condition for the 3-D Digital Waveguide Mesh. In Proceedings of the 2005 IEEE Workshop on Applications of Signal Processing to Audio and Acoustics (WASPAA 2005), pp. 191-194, New Paltz, NY, USA, October 2005. © 2005 IEEE. By permission.
  5. A. Kelloniemi, V. Välimäki, and L. Savioja. Simulation of Room Acoustics Using 2-D Digital Waveguide Meshes. In Proceedings of the 31st IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP 2006), Vol. 5, pp. 313-316, Toulouse, France, May 2006. © 2006 IEEE. By permission.
  6. A. Kelloniemi. Frequency-Dependent Boundary Condition for the 3-D Digital Waveguide Mesh. In Proceedings of the 9th International Conference on Digital Audio Effects (DAFx-06), pp. 161-164, Montreal, Canada, September 2006. © 2006 by author.
  7. D. T. Murphy, A. Kelloniemi, J. Mullen, and S. Shelley. Acoustic Modeling using the Digital Waveguide Mesh. IEEE Signal Processing Magazine, accepted for publication, March 2007. © 2007 by authors and © 2007 IEEE. By permission.
  8. A. Kelloniemi, P. Huang, V. Välimäki, and L. Savioja. Spatial Audio and Reverberation Modeling using Hyperdimensional Digital Waveguide Meshes. Helsinki University of Technology, Laboratory of Acoustics and Audio Signal Processing, Report 80, Espoo, Finland, November 2006. EURASIP Journal on Applied Signal Processing, submitted for publication on September 19th, 2006. © 2006 by authors.

Keywords: acoustic signal processing, architectural acoustics, FDTD methods, modeling, visualization

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© 2006 Helsinki University of Technology

Last update 2011-05-26