This study reports the source levels of clicks recorded from free-ranging white-beaked dolphins (Lagenorhynchus albirostris Gray 1846). A four-hydrophone array was used to obtain sound recordings. The hydrophone signals were digitized on-line and stored in a portable computer. An underwater video camera was used to visualize dolphins to help identify on-axis recordings. The range to a dolphin w...

Receptions, from a ship-suspended source (in the band 50-100 Hz) to an ocean bottom seismometer (about 5000 m depth) and the deepest element on a vertical hydrophone array (about 750 m above the seafloor) that were acquired on the 2004 Long-Range Ocean Acoustic Propagation Experiment in the North Pacific Ocean, are described. The ranges varied from 50 to 3200 km. In addition to predicted ocean ...

This paper describes an underwater acoustic communication experiment executed in the North Sea near Norway. A submarine broadcast direct-sequence spread-spectrum signals with data rates of 167 and 33 bit/s. The receiver station was a surface ship with a towed hydrophone array. As the platforms sailed away from each other the SNR at the receiver progressively dropped, with a continuously changin...

The Prototype International Data Center (PIDC) began standard processing of data from the first of the new International Monitoring System’s (IMS) hydrophone stations in November 2000. The station (designated HA08) is located off the Chagos Archipelago in the Indian Ocean (Lawrence et al, 2000). This is the first IMS hydroacoustic station that allows for coherent multi-sensor waveform processin...

A method is described for comparing the sensitivity of two hydrophones over the frequency range 1-15 MHz. This technique forms the basis for the dissemination of national ultrasonic standards in the U.K. over this frequency range. A reference hydrophone is placed in an ultrasonic field and then the device being calibrated is substituted and the two output voltages are compared. This substitutio...

An inexpensive animal recording and tracking system was designed, which uses sound-recording buoys deployed at several locations simultaneously in a passive hydrophone array. Each buoy contains a global positioning system ~GPS! Location logger, a stereo digital audio tape ~DAT! recorder with a hydrophone connected to one channel, and a VHF radio signal for time synchronization connected to the ...

The maximum value of acoustic pressure within an ultrasonic beam is limited by acoustic saturation. The t oretical basis for acoustic saturation has been analyzed previously. In this work, a high-power pulse source is used to drive acoustic pressure levels from an ultrasonic beam to saturation. An automatic procedure determines the field’s beam axis using a calibrated Marconi PVDF hydrophone. T...

We use a topology optimization method to design 1-3 piezocomposites with optimal performance characteristics for hydrophone applications. The performance characteristics we focus on are the hydrostatic charge coefficient d spd h , the hydrophone figure of merit d spd h g spd h , and the electromechanical coupling factor k spd h . The piezocomposite consists of piezoelectric rods embedded in an ...