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Sound absorption of snow

Theoretical modeling based on x-ray micro-tomography and integral geometric measures
: Maysenhölder, W.

Mace, B.R. ; Institute of Sound and Vibration Research, Southampton:
Proceedings of NOVEM 2009. Noise and vibration: Emerging methods. CD-ROM : Keble College, Oxford, 5th - 8th April 2009
Southampton: Univ. of Southampton, 2009
ISBN: 978-0-85432-900-7
12 pp.
NOVEM Conference <3, 2009, Oxford>
Conference Paper
Fraunhofer IBP ()

Measurements of sound absorption of porous materials can often be reproduced theoretically with sufficient accuray. Usually this is achieved by adaption of a few parameters of an absorption model. Ideally one would like to predict these parameters ab initio, i. e. without fitting, from the geometric structure of the porous material. Steps in this direction have been taken on the basis of combined measurements of absorption and microstructure performed on various snow samples at the Swiss Federal Institute of Snow ans Avalanche Research in Davos. The 3D images from X-ray micro-tomography were analyzed with the software MAVI (Modular Algorithms for Volume Images), which calculates numerous integral measures of the geometric structure including the Minkowski functionals (corresponding to porosity, inner surface and curvature integrals). The question is how many and which geometric parameters are needed for a satisfactory prediction of sound absorption. In general the Minkowski functionals will not suffice. However, they appear to be adequate for the approximate prediction of thermal effects. The measured absorption of the snow samples could be reproduced fairly well by the simplified version of wilson's relaxation model taking porosity and thermal relaxation time as deduced from the geometric analysis and using only two adjustable parameters.