A study on the sound transmission loss of a new lightweight hemp/bio-epoxy sandwich structure

Due to the increasing awareness around the environmental crisis and the depletion of petroleum resources, together with the inherent issues connected with the use of composite systems such as their disposal and recycling and the health problems associated with the use of some raw materials, new legislative rules on global scale have been promulgated to fight environmental issues and will be hoping adopted by several countries. Based on these considerations, the new generation of composite systems will have to minimize the environmental impact with a more efficient use of energy resources and materials and where possible, replace synthetic or petroleum materials with more sustainable components, like natural ones. Therefore, the aim of this paper is to investigate the sound transmission loss of a new sandwich structure in bio-composite material based on hemp fibers and bio-epoxy resin in order to further extend the application fields of natural fibers composite (NFC) materials. Measurements in the impedance tube were first used to assess the sound transmission loss at normal incidence. By using measured mechanical properties, a Finite Element Method was used to predict sound transmission loss in the same boundary condition. Finally, the so determined mechanical model has been used to predict the sound transmission loss in a diffuse field.