Abstract
Some synthetic materials commonly used in noise control systems, such as absorbent fibres, can have a potential harmful effect on human health and the environment. For this reason, searching of new sound absorbent materials is an active field of research. In the current work, natural fibres are presented as a potential alternative to the traditional fibrous materials, since the sound attenuation performance of the former can be good and these fibres can also be easily recycled from industrial scrap.
The main goal of this work is the acoustic characterization of natural fibres. The procedure here proposed focuses on measuring the flow resistivity of these materials through a steady flow experimental setup. This technique has been previously implemented by the authors, showing good agreement with theoretical models for fibreglass. Finally, a Delany and Bazley type theoretical acoustic model is proposed for coconut and sisal fibres through an experimental curve fitting method, since the results available in the bibliography are not accurate enough. Also, these properties are validated by comparing experimental measurements of the transmission loss (TL) of a silencer prototype with FEM computations.
