A Self-Consistent Approach for the Acoustical Modeling of Vegetal Wools

In the green buildings field, biobased materials such as vegetal wools are not only good candidates for thermal insulation but also for noise attenuation. Indeed, these materials (including e.g. hemp or flax wools) are characterized by high sound absorbing properties. However, in order to optimize their acoustical performances, it is necessary to take into account the vegetal fibres specificities in the modeling such as their heterogeneities in size and shape, but also their orientation. Thus, a Self-Consistent Method (SCM) with cylindrical geometry is developed to model the intrinsic parameters and the sound absorption coefficient of vegetal wools. The specificity of this Self-Consistent approach is based on the energy equivalence between a generic inclusion, representative of the vegetal wools physical and geometrical properties at microscopic scale, and the homogeneous equivalent medium at the macroscopic scale. After validation of the model by comparing results with experimental data, the aim is to optimize the acoustical performances by varying parameters such as porosity and airflow resistivity (indirectly via density and fibres radii). Moreover, the SCM can also be used to determine vegetal wools thermal performance. Thus, it offers the opportunity to develop an acoustical and thermal joint approach by identifying common characteristic parameters.