Improving the performance of MiniCan low noise hydrophone

Abstract

The MiniCan hydrophone is a small, easy to build, preamplified hydrophone with similar characteristics in sensitivity and self noise to larger and more expensive commercial devices. Previous work on the design showed a very promising performance, though it proved to have a flat sensitivity response of only up to 14 kHz. Unknown were also the effects that the aluminum housing parts produced on the overall response and whether the cable of the hydrophone had some influence on the sensitivity. A new design was built and tested changing the dimensions of the aluminum housing for the hydrophone, resulting in an increase in the region of flat sensitivity response up to 20 kHz and acceptable response up to 30 kHz, due to an increase of the lowest mechanical resonance of the hydrophone. A resonance testing device was built to investigate the mechanical characteristic of the components of the design, discovering that the first resonance of the aluminum base of 34.6 kHz caused the first overall resonance of the assembled device. Measurements of the influence of the cable showed an acoustic variation of about 1 dB in relative response in the range of interest, which is up to 30 kHz. The measurements proved that better performance can be achieved on the basic MiniCan design by increasing the resonant frequency of the aluminum body housing component.