FRIDAY MORNING, 4 JULY 2008 ROOM 242B, 8:00 A.M. TO 3:00 P.M. Session 5aAAa Architectural Acoustics: New Frontiers in Room Acoustical Modeling I Murray Hodgson, Cochair The University of British Columbia, Department of Electrical and Computer Engineering, 2332 Main Mall, Vancouver, BC V6T 1Z4, Canada Vincent Valeau, Cochair Laboratoire d’Etudes Aérodynamiques (LEA), Université de Poitiers - ENSMA - CNRS, Bâtiment K, 40 Avenue du Recteur Pineau, Poitiers, F-86022, France Contributed Papers 8:00 5aAAa1. Multiresolution geometrical-acoustics modeling. Benjamin Markham Rensselaer Polytechnic Institute, Greene Bldg., 110 8th St., Troy, NY 12180, USA, markhb@rpi.edu, Paul Calamia Rensselaer Poly- technic Institute, Greene Bldg., 110 8th St., Troy, NY 12180, USA, calamp @rpi.edu Geometrical-acoustics GA modeling techniques assume that surfaces are large relative to the wavelengths of interest. For a given scenario, prac- titioners typically create a single 3D model with large, flat surfaces that sat- isfy the assumption over a broad range of frequencies. Such geometric ap- proximations lead to errors in the spatial distribution of the simulated sound field because geometric details that influence reflection and scattering be- havior are omitted. To compensate for the approximations, modelers typi- cally estimate scattering coefficients for the surfaces to account stochasti- cally for the actual, wavelength-dependent variations in reflection directionality. A more deterministic approach could consider a series of models with increasing geometric detail, each to be analyzed at a corre- sponding frequency band for which the requirement of large surface dimen- sions is satisfied. Thus, to improve broadband spatial accuracy for GA simu- lations, we propose a multiresolution modeling approach. Using scale model measurements of a corrugated wall, comparisons of our method with non-GA techniques, and some simple listening tests, we will demonstrate that multiresolution geometry provides more spatially accurate results than single-resolution approximations when using GA techniques, and that this improved accuracy is aurally significant. 8:20 5aAAa2. On the analysis of the time spreading of sound diffusers. Javier Redondo IGIC - Universitat Politècnica de València, Cra. Nazaret- Oliva S”N, E-46730 Gandia, Spain, fredondo@fis.upv.es, Rubén Picó EPSG - Univ. Politécnica de Valencia, c” Nazaret-Oliva s”n, 46780 Grau de Gandia, Spain, rpico@fis.upv.es, Mark R. Avis University of Salford, Acoustics Research Centre, Newton Building, M5 4WT Salford, UK, m.r.avis@salford.ac.uk Since the invention of sound diffusers three decades ago a substantial effort has been made to predict the acoustic behaviour of these structures. BEM methods are well established for this purpose after a systematic com- parison between simulations and experimental data. Volumetric methods such as finite element methods FEM or the finite difference time domain method FDTD are not often used, due to their large computational cost. However, near to far field transformations NFFT can overcome that problem. Recently some of the authors have shown that the FDTD method is a useful technique to analyse the time domain signature of sound diffusers. In this paper a careful analysis of the performance of diffusers in the time domain “time spreading” are reported, opening a new field of research. Invited Papers 8:40 5aAAa3. Diffraction modeling in acoustic radiance transfer method. Samuel Siltanen Helsinki University of Technology, P.O. Box 5400, 02015 TKK, Finland, Samuel.Siltanen@tml.hut.fi, Tapio Lokki Helsinki University ofTechnology, P.O. Box 5400, 02015 TKK, Finland, Tapio.Lokki@tkk.fi The room acoustic radiance transfer method is a solution to recently presented room acoustic rendering equation which formulates the mathematical basis for all the ray-based geometrical room acoustic modeling algorithms. The basic acoustic transfer method gives as accurate results as the state-of-the-art commercial room acoustic modeling software. However, the basic method still lacks, e.g., diffraction modeling and modeling of complex reflections from surfaces. In this paper we discuss different diffraction modeling methods in the light of the acoustic radiance transfer method. The problems as well as benefits of each diffraction modeling method are sum- marized to understand which one of them can be implemented together with acoustic radiance transfer. Finally, some implementation examples are given. 9:00 5aAAa4. Can also diffracted sound be handled as flow of particles? Some new results of a beam tracing approach based on the uncertainty principle. Uwe M. Stephenson Hafen City University Hamburg, Nelkenweg 10, 23843 Bad Oldesloe, Germany, post @umstephenson.de In computational room acoustics as well as noise immission prognosis efficient ray or beam tracing methods are well approved - but the problem of the neglected diffraction is still unsolved in general. The author’s successful approach of 1986 based on Heisenbergs uncertainty principle was extended to the more efficient beam tracing technique and presented at the ICA 2007. The algorithm has now been generalized to recursive higher order diffraction. Now, not only single edge, but also multiple edge diffraction could be simulated 5a FRI. AM 3759 3759 J. Acoust. Soc. Am., Vol. 123, No. 5, Pt. 2, May 2008 Acoustics’08 Paris