Abstract The experimental characterization of most of the hygrothermal properties of bio-based porous materials, which are characteristic for their double-scale porosity, requires for the samples to stabilize their liquid water content. Furthermore, such measurements often take several weeks to several months. In contrast, acoustical measurements can be realized very quickly by using simple and relatively inexpensive test benches such as Kundt's tube. In this article, we investigate the existence of relationships between the hygrothermal and acoustical parameters of the porous media (porosity, resistivity, tortuosity, etc.), in order to provide ways to by-pass hygrothermal measurements by performing an indirect characterization of the material properties using acoustical measurements. Two expressions have been found to properly estimate the thermal conductivity and the water vapor permeability of the studied hemp and sunflower pith composites from acoustical measurements. However, further tests will be needed in order to establish the limits of these estimations (for which materials and in which conditions are they applicable) and further research will be made to shed light on the cause of these relationships. These two properties are capital in the conception of new eco-responsible building materials since a low thermal conductivity helps to improve energy efficiency, and the water vapor permeability plays a major role on thermal inertia, moisture regulation and on comfort inside the building. With further research, these results are expected to accelerate the development of sustainable construction materials and to better consider the complex hygrothermal behavior of such materials.

中文翻译：

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大麻和向日葵复合材料的湿热和声学行为之间的关系

摘要 生物基多孔材料的大部分湿热性质的实验表征以其双尺度孔隙率为特征，需要样​​品稳定其液态水含量。此外，这种测量通常需要几周到几个月的时间。相比之下，声学测量可以通过使用简单且相对便宜的测试台（如昆特管）来快速实现。在本文中，我们研究了多孔介质的湿热参数和声学参数（孔隙率、电阻率、弯曲度等）之间的关系，以提供通过对材料进行间接表征来绕过湿热测量的方法使用声学测量的特性。已经发现两种表达式可以从声学测量中正确估计所研究的大麻和向日葵髓复合材料的热导率和水蒸气渗透率。然而，需要进一步的测试来确定这些估计的限制（它们适用于哪些材料和条件），并且将进行进一步的研究以阐明这些关系的原因。这两种特性是新型环保建筑材料概念的资本，因为低导热性有助于提高能源效率，而水蒸气渗透率对热惯性、湿度调节和建筑物内部的舒适度起着重要作用。随着进一步研究，