Pressure-particle acceleration underwater acoustic intensity sensor

Abstract

An underwater acoustic intensity sensor designed to measure one component of the acoustic intensity vector is discussed and evaluated experimentally. This sensor consists of a pressure transducer in the form of a piezoceramic hollow cylinder, and an accelerometer 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.’’ The probe body has syntactic foam endcaps that are adjusted in thickness to allow the entire assembly to be neutrally buoyant. It is coated with polyurethane for waterproofing while maintaining acoustical transparency in water. Each of the two transducers making up the intensity sensor is calibrated individually in both air and water. The integrated intensity probe is calibrated 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 that is in very close agreement to the predicted value using slow-waveguide acoustic theory. Some limitations in the experiments and future works are discussed. [Work supported by ONR, Code 321 MURI in Acoustic Transduction: Materials and Devices.]