Continued investigation of the use of passive resonators to improve the performance of a low frequency sonar transducer.

Abstract

In an earlier thesis, Ellsworth showed that the radiated power output (quantified by the gain in radiation resistance presented to the transducer) and directivity of a compact underwater transducer can be significantly improved by the use of a system of resonant scatterers. These resonant scatterers were termed "sympathetic resonators." In the present work, we verify the previous findings and extend the work to additional cases of interest. Specifically, we (1) employ equations requiring fewer assumptions and implement them using more accurate numerical techniques, (2) reproduce Ellsworth's calculations and provide graphical results for conical and planar circular configurations for the case of six passive acoustic resonators, (3) extend the theory to and provide results for two typei of linear arrays of passive acoustic resonators, (4) and finally, we consider an acoustic Yagi-Uda antenna-like configuration of passive acoustic resonators to improve the directivity of an underwater transducer. The results indicate that the conical configuration of six resonators is the best choice in terms of the gain in radiated power output, directivity along an acoustic axis, and minimum required number of resonators.