Effect of manufacturing procedure on the miniaturized flextensional transducers (Cymbals) and hydrophone array performance

This paper summarizes the effect of manufacturing procedure on the performance of an element as well as an array of cymbal type transducers. A finite element software ATILA, is used to model the cymbal element and optimized the dimension and materials based on the results. A maximum Receiving Sensitivity (RS) of -203 dB re 1V/μPa @ 1m is obtained analytically for a single element with 13mm diameter and a cavity depth of 600 micron and maximum RS of -192 dB re 1V/μPa @ 1m is obtained analytically for a single element with 19mm diameter and a cavity depth of 320 micron. Several prototypes were fabricated and tested the performances in Acoustic Test Facility at NIOT, which is National Accreditation Board of Testing and Calibration of Laboratories (NABL) certified. The RS showed a maximum value of only-182 dB re 1V/μPa @ 1m even with a preamplifier having a gain of 20dB for a 13mm cymbal array (1×5). The experimental results are matching well with modelled results for single elements. But expected array gain as per the numerical calculations were not obtained when connected elements in an array. It has been also observed that the d₃₃ values of cymbal elements in an array should be identical to get the predicted results. Extreme care should be taken to avoid high pressure from acting upon the apex of the end caps during gluing and other stages. Special care in gluing, blanking and forming operations combined with optimum force/torque is necessary in getting good array performance.