Green's Function Extraction from Atmospheric Acoustic Propagation
Technical Report,01 Oct 2015,31 Mar 2018
US Army Research Laboratory Adelphi United States
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A multiyear research project was conducted to determine the feasibility of using time reversal in conjunction with flow reversal, or similar signal processing methods, to extract the Greens function for outdoor sound propagation using sources in audible frequency ranges. Here we report the findings of this three-year Directors Research Initiative project. We present comparisons of the Greens function retrieval methods for an outdoor acoustic propagation channel by multidimensional deconvolution and cross correlation for different source waveforms. Of particular interest is the accuracy of the retrieved Greens function of an on impulsive sound source compared to that of an impulsive sound source. The retrieved Greens functions are used to estimate the pressure field response and compared to the actual measured response. The corresponding correlation coefficient and other measures are used to quantify the performance. To this end, outdoor acoustic experiments were conducted in an open field and forested area in southern Maryland. Results are presented for various source receiver ranges up to 600 m.