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The aim of this paper is to propose a novel sandwich panel, which would be suitable for sound absorption and airborne sound insulation, used as applied cladding or independent lightweight partition wall. As far as the authors are concerned, this is the first sheep wool-based sandwich panel using only natural materials. The structure was prepared using hydrated lime-based composite face sheets and a sheep wool-based core. Several parameters of the sandwich panel were determined, including sound absorption coefficient, airborne sound insulation, thermal conductivity, thermal resistance, compressive strength, and bending strength, respectively. The results indicate that the maximum sound absorption value of 0.903 was obtained at the frequency of 524 Hz in the case of the unperforated sample, 0.822 at 536 Hz in the case of the sample with 10% perforations, 0.780 at 3036 Hz in the case of the sample with 20% perforations, and 0.853 at 3200 Hz in the case of the sample with 30% perforations. The registered airborne sound insulation index of the panel was 38 dB. Based on the obtained data, it can be concluded that the studied panel recorded comparable values with other synthetic noise control solutions, which are suitable as applied cladding or an independent lightweight partition wall, with good acoustic properties.

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Plant fibres are materials that can increase energy savings, and they are being analysed for their reduced environmental impact. In this paper, three types of multi-layered panels were developed as environmentally friendly flax fibre-based products for building industry applications. The structural build-up of the panels is such that one layer of waste flax fibre was used as the core material in order to reduce the weight of the structure between two rigid perlite-based layers. The perlite was used in three varied grain sizes, resulting in three types of panels (S1, S2, S3). The mechanical, thermal and acoustic properties were recorded for all specimens. The influence of the perlite particles’ size, perforation diameter and perforation percentage of the multi-layered panels on the acoustic absorption properties was analysed and discussed. Summarising the results, the multi-layered composite panel S3 presented the best performance in regard to compressive strength and thermal conductivity, with S2 presenting the best bending strength. From the acoustic point of view, for the unperforated panels, the highest values of the sound absorption coefficient were obtained at 500 Hz for S1, α = 0.95, 315 Hz for S2, α = 0.89 and 400 Hz for S3, α = 0.84. The obtained values of the sound absorption coefficients were increased through the varied perforation diameters and percentages of the panels’ front face.

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