Benchmarking new wood fibre–based sound absorbing material made with a foam-forming technique

Abstract

A new sound absorbing material made from 100% softwood fibres by means of a foam-forming technique is introduced. In foam forming, a wet foam is created by mechanically mixing water, fibres and a surfactant. The air bubbles keep the wet fibres separate, and a highly porous fibre network is formed during drying. The sound absorption of foam-formed structures was measured by means of an impedance tube. The results showed that foam-formed softwood materials possessed a competitive sound absorption coefficient compared to different types of commercial sound absorber materials. The material is based on 100% softwood fibres without added binders and is semi-rigid and does not completely recover from compression. Improvement in the strength properties of softwood material can be obtained by using starch or cellulose microfibrils. The material could be used in indoor applications, for example, in replacing mineral wool acoustic ceiling panels or polyester non-woven materials in office acoustics products.