Reduction in edge effects for small panels characterized by a parametric array source

This study sought to explore effects of panel size on underwater acoustic transmission and reflection measurements made with a truncated parametric array source. The transmission loss (TL) and reflection loss spectra of aluminum panels of several different sizes were determined experimentally, and compared to predictions from plane wave theory in the 5-100 kHz frequency range. For the smallest panel size, there were significant discrepancies between experimental data and plane wave theory, which were attributed to contributions from edge-diffracted waves and interferences from the mounting fixture for the panel. For reflection measurements, the latter interference could be corrected for in part by measurement of the reflected signal from the sample holder (with no panel present), and subtracting this signal from reference and test panel waveforms. In order to reduce the contributions from edge diffracted waves in TL measurements, an alternative panel mounting system was investigated, which involved surrounding the panel in a reflective baffle. There was a significant improvement in agreement of experimental TL spectra with plane wave theory for the smallest aluminum panel when the baffle mounting arrangement was used.