Investigation of an underwater acoustic intensity vector sensor.

摘要

An underwater acoustic intensity sensor designed to determine the acoustic intensity vector by measuring acoustic pressure and the acoustic particle acceleration vector at the same location is discussed and evaluated experimentally. This sensor consists of a pressure transducer in the form of a piezoceramic hollow cylinder, and a pair of miniature accelerometers mounted inside of the cylinder. This is a pressure-acoustic particle-acceleration type of intensity probe, and is henceforth denoted as a “p-u-dot intensity probe” (p represents acoustic pressure and u-dot represents the time derivative of acoustic particle velocity). Two syntactic foam caps are attached to both ends of the hollow cylinder. This is done to assure that the entire assembly is neutrally buoyant, so that the sensor measures the acoustic particle acceleration with minimum adverse effect due to the inertia caused by entrained water mass. Polyurethane is used as a coating to waterproof the probe body. Each of the transducers making up the intensity sensor is calibrated individually in both air and water.; The integrated intensity sensor is tested in a water-filled plane wave tube. It is shown that this neutrally buoyant underwater acoustic p-u-dot probe measures one component of sound intensity over the frequency range 100 ≤ f ≤ 1600 Hz. The measurements are in very close agreement with the predictions made using slow-wave guide acoustic theory. A calibration under free-field conditions is then performed under the ice of a flooded quarry.; The two-dimensional acoustic intensity field is mapped for various acoustic source configurations in a small laboratory tank. These include a single spherical source and a pair of spherical sources that vibrate in or out of phase with each other. The sinusoidal signal of 5kHz is gated in all of these experiments in order to suppress the effects of environmental reflections. The acoustic intensity field from two closely spaced, interacting spherical radiators is predicted. The predictions compare well with the measured intensity field.; It is concluded that an accurate acoustic intensity measurement, even close to the acoustic sources in water, can be achieved by using a neutrally buoyant intensity probe consisting of a pressure sensor and an inertial vector sensor. Higher frequency measurements require a small probe, and the feasibility of practical implementation of miniature accelerometers into the intensity probe has been proven successful, with some limitations. (Abstract shortened by UMI.)