High Resolution Acoustical Imaging
PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB
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Pressure waves, detected by an array of receivers, can be analyzed to determine the location of the acoustic source, or the location of objects which the waves encountered along their path. This thesis examines high resolution methods which use a linear array to locate stationary objects which have scattered the pressure waves. Several new methods are explored through simulations in air. A theoretical examination of all of the basic and high resolution acoustical imaging methods is first conducted. These methods include holographic reconstruction, beamforming, a correlation method, autoregressive-moving average ARMA spectral estimators and minimum energy methods. This examination summarizes the well-known ability of these methods to locate sound sources while making some new observations on the ability of these methods to located sound scatterers. One of the methods which was examined used the concept of a fictitious source. This concept is developed to yield a new imaging approach called the pattern-match method which is similar to the temporal signal processing technique called the matched filter. In addition, a new technique for comparing signals is used to develop a variation of the pattern-match method called the mismatch method. A series of simulations is used to examine the ability of both methods to locate either one or two acoustic sources.