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Please use this identifier to cite or link to this item: http://hdl.handle.net/1860/78

Title: Hydrophone spatial averaging corrections from 1 to 100 MHz
Authors: Radulescu, Emil George
Keywords: Hydrophone;Underwater acoustics -- Instruments;Sound -- Measurement
Issue Date: 31-Dec-2002
Publisher: Drexel University
Abstract: The purpose of this work was to develop and experimentally verify a set of robust and readily applicable spatial averaging models to account for ultrasonic hydrophone probe's finite aperture in acoustic field measurements in the frequency range 1 - 100 MHz. Electronically and mechanically focused acoustic sources of different geometries were considered. The geometrics included single element circular sources and rectangular shape tranducers that were representative of ultrasound imaging arrays used in clinical diagnostic applications. The field of distributions of the acoustic sources were predicted and used in the development of the spatial averaging models. The validity of the models was tested using commercially available hydrophone probes having active element diameters ranging from 50 to 1200 um. The models yielded guidelines which were applicable to both linear and nonlinear wave propagation conditions. By accounting for hydrophones' finite aperture and correcting the recorded pressure-time waveforms, the models allowed the uncertainty associated with determining the key acoustic output parameters such as: Pulse Intentsity Integral (PH) and the intensities derived from it to be minimized. In addition, the work offerred a correction factor for the safety indicator Mechanical Index (MI) that is required by AIUM/NEMA standards. The novelty of this research stems primarily from the fact that, to the best of the author's knowledge, such comphrehensive set of models and guidelines has not been developed so far. Although different spatial averaging models have already been suggested, they have been limited to circular geometries, linear propagation conditions and conventional, low megahertz medial imaging frequencies, only. Also, the spatial averaging models described here provided the necessary corrections to obtain the true sensitivity versus frequency response during calibration of hydrophone probes up to 100 MHz and allowed for a subsequent development of two novel calibration methods.
URI: http://dspace.library.drexel.edu/handle/1860/78
Appears in Collections:Drexel Theses and Dissertations

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