THE DESIGN OF LOW-FREQUENCY UNDERWATER ACOUSTIC PROJECTORS - PRESENT STATUS AND FUTURE-TRENDS

This paper first presents the difficulties that dominate low-frequency projector design problems in sonar and oceanographic applications. These are related to the size of the projector, the low radiation resistance, the acoustic interaction effects in arrays, as well as the requirements due to deep submergence. It then describes and compares present low-frequency projectors and analyzes future trends associated with transducer shapes and dimensions or with the type of active materials used for the driving part. Finally, it discusses the different modeling approaches and provides in particular an insight into the respective advantages and disadvantages of classical equivalent circuit models and numerical models - mainly those using the finite-element method. Several modeling examples are briefly introduced.