Sound Propagation in Activated Carbon felts

Granular activated carbon materials have been studied for some years and are now well-known for their ability to absorb sound at low-frequencies. They are able to outperform standard granular materials in this regard due to the presence of sorption processes (absorption and adsorption) in nanopores. Activated carbon fibres have a similar microstructure but are light-weight and easier to use as they do not need binders. The aim of the study is to investigate the ability of activated carbon fibres to effectively absorb low frequency sound. The acoustical properties of activated carbon fibres are measured in an impedance tube to assess the importance of parameters such as specific surface area, fibre diameter, porosity and pore size at different scales. A model to predict the acoustic behaviour of the activated carbon fibres is also developed. This model takes into account different scales of porosity and the presence of sorption. Possible applications of activated carbon fibres including exhaust silencers and loudspeaker cabinets are discussed.