Highly directional acoustic receivers.

The theoretical directivity of a single combined acoustic receiver, a device that can measure many quantities of an acoustic field at a collocated point, is presented here. The formulation is developed using a Taylor series expansion of acoustic pressure about the origin of a Cartesian coordinate system. For example, the quantities measured by a second-order combined receiver, denoted a dyadic sensor, are acoustic pressure, the three orthogonal components of acoustic particle velocity, and the nine spatial gradients of the velocity vector.

Low-frequency echo-reduction and insertion-loss measurements from small passive-material samples under ocean environmental temperatures and hydrostatic pressures.

System L is a horizontal tube designed for acoustical testing of underwater materials and devices, and is part of the Low Frequency Facility of the Naval Undersea Warfare Center in Newport, Rhode Island. The tube contains a fill fluid that is composed of a propylene glycol/water mixture. This system is capable of achieving test temperatures in the range of -3 to 40 deg Centigrade, and hydrostatic test pressures in the range 40 to 68,950 kPa.

The design, fabrication, and measured acoustic performance of a 1-3 piezoelectric composite Navy calibration standard transducer.

The design, fabrication, and acoustic calibration of a new 1-3 piezoelectric composite-based U.S. Navy standard (USRD-F82) are presented.

Beamformed nearfield imaging of a simulated coronary artery containing a stenosis.

This paper is concerned with the potential for the detection and location of an artery containing a partial blockage by exploiting the space-time properties of the shear wave field in the surrounding elastic soft tissue. As a demonstration of feasibility, an array of piezoelectric film vibration sensors is placed on the free surface of a urethane mold that contains a surgical tube. Inside the surgical tube is a nylon constriction that inhibits the water flowing through the tube.