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

Abstract 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 δ = m , δ 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 δ 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.