Influence of the thickness and the attenuation coefficient of a backing on the response of transducers

In this paper, the characteristic mechanical. impedance of an absorbing medium (backing) is expressed in terms of its thickness T-B and the tangent of the phase angle (tan delta = m, delta is the loss angle). In fact, the backing has been considered as a lossy transmission line. Then, using the model of Mason's circuit, the electrical impedance and radiated power of an in-air backed transducer will be expressed in terms of tan delta and T-B. It is shown that the characteristics of such transducers do not change if the thickness is scaled down and the product mT(B) stays constant. The same properties have been obtained for backed transducer bars using a finite element method (FEM) analysis.