Wide bandwidth and low-frequency target response measurements with a large PVDF sheet source outside the laboratory

Abstract

It is demonstrated that elastic response features in the few kilohertz frequency range and at higher frequencies can be observed using a large, acoustically transparent PVDF sheet source. The source was operated in both the impulse mode [Kaduchak et al., J. Acoust. Soc. Am. 97, 2699–2708 (1995)] and with tone burst excitation. It was used in Lake Union (Seattle) to measure resonances and other elastic features of a stainless steel spherical shell having a radius of 29.8 cm. Both the source and sphere were supported from the APL barge. One especially noteworthy feature of the source is its ability to generate tone bursts that turn on and off abruptly. This is because of the absence of resonances of the source. The potential applications of sheet sources of this type are not limited to laboratory experiments. [Work supported in part by the Office of Naval Research and by APL.]