APPLICATION OF THE FINITE-ELEMENT METHOD FOR MODELING BACKED TRANSDUCERS

To model backed transducers by the finite-element method, the main dra wback is generally the large size of the numerical problem. Thus, the aim of this paper is to show how the backing mesh can be quite limited . For this purpose, the backing is considered as a lossy transmission line. Then, the equivalent acoustic impedance of the backing is expres sed in terms of its thickness T-B and the tangent of the phase angle ( tan delta). It will be shown that the characteristics of a backed tran sducer (electrical impedance, acoustic radiated power, etc.,...) can s tay unchanged if the thickness T-B is scaled down and tan delta is sca led up, keeping the product T-B tan delta constant. Finally, finite-el ement results are successfully compared with measurements results usin g lithium niobate backed transducer. (C) 1996 Acoustical Society of Am erica.