The present study deals with the acoustic properties of lime/hemp concrete manufactured by compression molding. In order to efficiently contribute to sustainable development, building materials must consider energy consumption, environmental impact of the chosen materials as well as indoor comfort of the construction. Lime/hemp concrete, a mixture of plant based aggregates and hydraulic aerated binder, has proven to have good mechanical, hygrothermal and thermal isolation properties.

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... y, given the porous nature of hemp particles, lime/hemp concrete can be used as an acoustic absorption material for domestic buildings. For these reasons, lime/hemp concrete has been increasingly used as an environmentally friendly construction material. In this study, acoustic absorption and impedance are characterized for a given lime/hemp mass ratio. The influence of particle orientation (anisotropy), density, thickness, and gradient of density is investigated. While anisotropy does not affect acoustic properties, a gradient of density tends to broaden the frequency range for acoustic absorption. Impedance and absorption coefficient of the material with a density gradient are evaluated experimentally and compared using a model based on the multilayered fluid approach. Finally, it is also shown that the absorption coefficient of lime/hemp concrete can be effectively modeled using the multiscale approach given a double scale porosity of the hemp particles. The outcome of the present study will help establishing optimal molding parameters to obtain advantageous properties concrete, both for mechanical and acoustical purposes.