Transmission loss in an alberich tile

Abstract

Elastromeric tiles have been developed as effective reflectors of hull- born acoustic energy. To aid designers theoretical models have been developed to predict performance. Here we present a scheme based upon the finite element method which considers the tile as being composed of an infinite doubly periodic plane with fluid above and below. The incident wave on the top fluid region produces reflected components and, depending on the nature of the structure, transmitted waves into the lower fluid region beneath. Higher scattering order waves may be excited which either decay with distance from the plane or propagate to the far field. Associated with each wave is a wave number which if real refers to a propagating wave, and a complex amplitude, which depending on fluid region is either a transmission, or a reflection coefficient. The structure is composed of truly viscoelastic material which is frequency dependent. Within the tile are arranged cylindrical voids which are typical in ALBERICH type coatings. We present results for a specific tile's transmission loss (10 Log of the transmission coefficient). Comparison is made with measurement.