Comprehensive model combination for the calculation of the acoustic impedance of granular media

For the calculation of the acoustic impedance of granular media numerous empirical and phenomenological models are available. Most of these models are based on parameters such as void content, airflow resistance and a parameter describing the inner structure of the absorber such as the tortuosity or the structure factor. However, these parameters cannot be used directly in material science, to adjust the material composition of porous concrete or porous asphalt with regard to the acoustic optimization. For such material compositions geometrical parameters of the mineral material like the grain-size distribution and binder content are decisive. In material science, however, models are available to calculate e.g. The airflow resistance as a function of the void content or the void content as a function of the grain-size distribution. One of the latter is the compressible packing model. A combination of material models and acoustic models could allow to calculate the acoustic impedance and absorption coefficient, respectively directly from the grading curve of porous materials.