Sandwich Transducer, Simplified Mathematical Model (II)

To each of the infinite set of solutions obtained from the sandwich transducer general equation a numerical index is associated. This numerical index, G, called Gain Index, refers to the transducer quality. For any particular sandwich the maximum value, G _M, of the gain index is obtained together with the thickness of the three component layers of the transducer. The Langevin's equation is deduced as a particular case of the most general equation by making the radiating head thickness equal to a quarter of wavelength. The use of thin piezoceramics is also justified.