The acoustic characteristics of dense and porous piezoceramic disc hydrophones have been studied by finite element modelling (FEM). The FEM results are validated initially by an analytical model for a simple disc of dense piezoceramic material and then it is extended to a porous piezoceramic disc replicating a foam-reticulated sample. Axisymmetric model was used for dense piezoceramic hydrophon...

Ultrasound image guidance is widely used in minimally invasive procedures, including fetal surgery. In this context, maintaining visibility of medical devices is a significant challenge. Needles and catheters can readily deviate from the ultrasound imaging plane as they are inserted. When the medical device tips are not visible, they can damage critical structures, with potentially profound con...

A passive sonar array designed for tracking diving sperm whales in three dimensions from a single small vessel is presented, and the advantages and limitations of operating this array from a 6 m boat are described. The system consists of four free floating buoys, each with a hydrophone, built-in recorder, and global positioning system receiver (GPS), and one vertical stereo hydrophone array dep...

To track highly directional echolocation clicks from odontocetes, passive hydrophone arrays with small apertures can be used to receive the same high frequency click on each sensor. A four-hydrophone small-aperture array was coupled to an autonomous acoustic recorder and used for long-term tracking of high-frequency odontocete sounds. The instrument was deployed in the spring of 2009 offshore o...

An absolute hydrophone calibration technique using ultrasonic far-field with optical interferometry was extended to 40MHz to evaluate the sound pressure amplitude generated by medical ultrasound equipment. A 1-mm nominal radius plane transducer was the calibration sound source for an ultrasonic far-field at 50mm propagation distance at 40MHz. The transducer’s effective radius was 0.88mm at 40MH...

Approximation of acoustic Green’s functions through cross-correlation of acoustic signals in the ocean is a relatively young field that has become an area of interest over the past few years. Although the amplitudes of these estimates generally differ from those of the true Green’s Function, the estimated arrival structure can be highly accurate. Interhydrophone travel times extracted from thes...