In-situ sound absorption of ground surfaces: Innovative processing and characterization methods

Invited paper

Jacques Cuenca

Siemens Industry Software

Tuesday 2 june, 2015, 16:40 - 17:00

0.7 Lisbon (47)

The present paper proposes refined methods for the in-situ measurement of ground sound absorption and their use for the estimation of the physical properties of porous pavements. A first part of the work is devoted to the development of two sound absorption measurement techniques using line arrays of several microphones, optimally spread. The validation of the methods is performed by numerically evaluating their robustness to physical uncertainty and measurement variability, and through their application on specifically-designed test setups. In particular, it is shown that the new methods considerably improve the accuracy of the estimation and that the frequency range of validity can be extended by controlling the spatial distribution of the microphones. When limiting the setup to two sensors, both processing methods fall back to the ISO standard specifications, thus guaranteeing compliance with well established methods. The second part of the paper focuses on the extraction of four intrinsic parameters of porous ground surfaces as defined in the Hamet-Bérengier model, namely the porosity, the tortuosity, the flow resistivity and the thickness. These parameters are estimated by fitting the model on the sound absorption coefficient by means of an optimisation approach. The method benefits from the reduced uncertainty of the proposed measurement techniques and is applied to different ground surfaces such as gravel and outdoor road asphalts. One of the main benefits of such an inverse estimation methodology is the replacement of direct measurements of asphalt properties.

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