ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

4pEA1. Theoretical model for a (3,1) drive low-frequency piezofilm hydrophone.

P. Philip Thomson

Dept. of Appl. Phys., School of Phys., Univ. of New South Wales, Sydney 2052, Australia

An innovative (3,1) drive transducer design has been discussed in the literature [J. J. Bhatt, P. P. Thomson, and P. R. S Pillai, J. Acoust. Soc. Am. 94, 3053--56 (1993)] using a poled piezofilm adhered to a driver pin which is fixed to the center of a rigidly clamped circular plate. This paper attempts to analyze the above transducer for a particular frequency range in terms of the theory of transverse vibrations of a clamped circular plate carrying a concentrated mass at its center [R. E. Roberson, J. Appl. Mech. 18, 349--352 (1951)]. The system satisfies the requirements for vibrational analysis and the natural frequencies can be estimated from above theory. A statistical approach is made to calculate the theoretical sensitivity below resonance. The prestretched piezofilm acts as a longitudinal vibrator with the electric field perpendicular to its length and the transducer system can be represented by a six-terminal network with an electrical input voltage driving the mechanical load acting only on one edge of the piezofilm. The surface strain developed in the diaphragm in response to the acoustic pressure and electroacoustic sensitivity are evaluated by thin plate theory and piezoelectric theory. The calculated values are in agreement with experimental results.