Frequency Response Function for Prediction of Planar Cellular Plastic Foam Acoustic Behavior

Abstract

In this paper, Biot's dynamic poroelasticity theory is applied for deriving theoretical complex dynamic stiffness solutions for fixed lower surface, infinite planar cellular plastic foams with permeable and impermeable upper surfaces. A model using impulse pressure excitation to derive and acquire the acoustic response functions of foams is performed. The derived theoretical dynamic stiffness equations can also be used for predicting the dynamic stiffness of composite foams. The dynamic stiffness of a composite foam can be seen as a series combination of the dynamic stiffness of single planar foams according to their stacking order. Using the derived complex dynamic stiffness equations, frequency response functions of acoustic impedance, reflection coefficient, and sound absorption coefficient are obtained. Experimental results from earlier studies are used to validate the derived frequency response function. The experimental acoustic properties of planar polyurethane foams with the same cellular skeleton at various thicknesses, are compared to the predicted properties. The influences of thickness on the acoustic properties are discussed.

Keywords

cellular plastic foam acoustical property theoretical solution frequency response function impedance tube

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