Optimising open porous foams for acoustical and vibrational performance

A computational method for designing optimal arrangements of multi layer noise and vibration treatments in general and porous open cell foam in particular, is discussed. The method is based on finite element solutions to Biot's equations for poroelastic materials which are used to evaluate cost functions and gradients. The porous material is parameterised using scaling laws linking the microscopic properties to the averaged elasticity, flow resistivity and characteristic viscous and thermal lengths. The cost function is either in terms of weight or in terms of the pressure response in a finite cavity, complemented with constraints on the other. The results suggest that changes of the microscopic properties of the foam may be made to adapt the foam to a specific environmental condition and thereby achieve improved acoustic behaviour as well as reduced weight.