Standard target calibration: Practical inter-comparison with planar surface targets and calibrated transducers

This contribution presents the inter-comparison of three different methods for obtaining amplitude and phase correction functions for broadband transducers used within an experimental scientific echo sounder. The standard target method is compared to the use of a planar boundary and a conventional calibrated PVDF membrane hydrophone. These correction functions enabled a fully corrected scientific active sonar system to be deployed for measuring the statistical repeatability of a production run of standard target spheres using low cost materials such as aluminum. Previous experience had shown that the acoustic characteristics of aluminum stock differed from billet-to-billet and even within a billet. Thus a laboratory method of establishing the efficacy of low-cost standard targets was developed.