Acoustic performance of voided materials: dependency on frequency and depth

A brief discussion is given of some of the theoretical techniques which have been proved reliable for modelling the propagation of acoustic waves through novel decoupling materials. These materials are composed of viscoelastic polymers in which air is introduced either in the form of microvoids (small perforations) or as large moulded macrovoids. Dynamical effective medium theory for scattering predictions is combined with pressure dependency relations for depth behaviour to estimate the decoupling performance of some typical materials at a range of specified depths and frequencies. Comparisons are then made with measurements taken in the deep sea and it is shown that, for these materials, the modelling of both frequency dependence and the degradation with depth is generally very good indeed