Conference_programme: 18.8 - Recent trends in numerical modeling: protocols and reliability
Lecture: Simulation of multiple Sound Particle Diffraction based on the Uncertainty Relation - a revolution in noise immission prognosis; Part I: Principle and Method
Author(s): Stephenson Uwe M.
Summary:
In room acoustics, as well as in free field, computational methods are often based on geometric and energetic room acoustics, frequently using the mirror image source method to compute reflections, and the detour-method to compute screening effects. This combination is highly inefficient, often ambiguous or even wrong. Numerical Monte Carlo- methods as the sound particle simulation method have hardly been used in noise immission prognosis up to now. However, their combination with the sound particle diffraction method based on the uncertainty relation (UR) offers fascinating possibilities. Its idea: the closer the by-pass distance of a sound particle to an edge, the more strongly it is deflected. The deflection is governed by a ‘Diffraction Angle Probability Density Function’ (DAPDF) derived from Fraunhofer diffraction. By this straight-forward method, relevant diffraction events are automatically found. To account for simultaneous by-passing several edges, a summable ‘Edge Diffraction Strength’ is introduced. Using the DAPDF component wise, this method was extended to 3D. To find diffracting edges, ‘virtual walls’ are introduced by an algorithm to subdivide the space into convex sub-spaces. In the last decade, many problems of different scenarios of multiple diffractions have been investigated and successfully solved. These developments and investigations are described in this paper. It could be shown: applying the UR is a successful approach to solve many problems with multiple diffractions that are unsolvable by analytical methods. The alternative method of a recursive splitting up of sound particles at each diffraction was dropped to avoid an explosion of computation time. Nevertheless, the efficiency of the whole simulation could be proven. The method was meanwhile implemented in the recent release of the commercial software SoundPLANnoise. The results were validated by comparison with Svenssons wave theoretical secondary edge source model. Meanwhile they were also evaluated by measurements with multiple diffractions. See next paper.
Corresponding author
Name: Prof Uwe M. Stephenson
e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
Country: Germany
