Inverse estimation of the non-acoustical parameters of loose granular absorbers by Simulated Annealing

Abstract

Absorbing materials are fundamental for the acoustic design of buildings. They are used for increasing the insulation from either outdoor or neighbour noise and for raising the acoustic comfort of dwellings. If environmental and health issues are not of concern, conventional sound absorbers, namely synthetic foams and fibrous materials, offer an excellent acoustical performance at a moderate cost. However, the current trend towards eco-efficient products encourages the enhanced use of natural fibre and loose granular recycled materials. Whatever the material type, a model is required to reliably predict its acoustical performance. The microstructural Champoux–Stinson model has demonstrated to provide consistent acoustical predictions once five non-acoustical parameters are given. Instead of measuring these non-acoustical parameters, which is a rather sophisticated and time consuming procedure, an inverse method, based on Simulated Annealing, is proposed in this paper to estimate them from a single and simple measurement of the absorption coefficient. Experimental results on two samples of loose aquarium gravel validate the proposed inverse method.