What Is The Actual Influence Of A Nano-Fibrous Membrane On The Acoustical Property Of Porous Substrate?

There is a general lack of publications on the acoustical and related non-acoustical properties of nano-fibrous media. Existing publications typically present scanning electron microscope images of these media together with the acoustic absorption coefficient or transmission loss data (e.g. [1,2]). These works often discuss the nano-fibre production process, quote data on the fibre diameter and surface density for nano-fibrous membranes produced as a result of the reported process. However, little or no information is usually presented on the material pore structure, membrane thickness or bulk density. No effort is made to explain the observed acoustical performance of nano-fibrous membranes using a valid theoretical or semi-empirical model [1,2]. This paper describes the problems associated with acoustic and related non-acoustic characterisation of these materials. It attempts, probably for the first time, to use a Biot- and Darcytype mathematical models to explain the observed acoustical and related non-acoustical behavior of nano-fibres. It identifies theoretical gaps related to the physical phenomena which can be responsible for the observed acoustical behaviour of nano-fibrous membranes and it makes recommendations to fill these gaps.