Development of a cost-effective shock wave hydrophone

The design of a new wideband, quantitative shock wave hydrophone is presented. The sensor not only has a wideband (>50 MHz) and linear (up to 100 MPa) response, but it also operates in a measurement environment in which the hydrophone element´s sensitivity changes as a function of shock wave exposure. Thin films of polyvinylidene difluoride (PVDF) were used in a disposable hydrophone configuration. A self-monitoring feature, based on the change in hydrophone electrode resistance as the electrode materials are removed by shock wave action, indicates that the hydrophone element needs to be replaced. Development efforts include: 1) reducing the manufacturing costs; 2) determining the relationship between electrode resistance and hydrophone sensitivity; 3) developing a resistance monitoring approach; and 4) rapidly making reliable electrical connection to the disposable hydrophone elements. Acoustical characterization data indicate that the hydrophones fulfill the requirements for accurate, wideband measurement of lithotripter fields; the disposable feature makes the system cost effective for research, quality assurance and regulatory submissions