File:A comparative study of acoustic models in a range-independent shallow water environment (IA acomparativestud1094530810).pdf

Project GEMINI was initiated to study the sound pressure fields in a range-independent, benign shallow water environment. The project consisted of five separate experiments conducted at a shallow site (approx. 20 m), a relatively deep water site (approx. 60 M) and a 30 m deep site previously studied by Rubano (1980). The experiments were carried out at both 50 and 140 Hz with measurements collected on two hydrophones at each site. The resulting data set was analyzed and compared to various acoustic propagation models approved or under consideration for inclusion in the Navy's Ocean Atmospheric Master Library (OAML). The following models were considered in the analysis: PE, utilizing the OAML approved LFBL database, FEPE and SNAP. FEPE and SNAP used a Hamiltion 'point' geoacoustic model as bottom model inputs. The models show varying ability to accurately model the average transmission loss (TL) and TL data intensity fluctuations at both frequencies. PE was not generally effective in modelling the TL data while FEPE was only slightly more accurate. SNAP proved to be the most successful predicting the average TL and TL data fluctuations. SNAP was especially accurate in modeling TL at the Rubano site where an accurate Hamilton geoacoustic model was derived. SNAP's accuracy in modeling TL was significantly degraded at the deep and shallow water sites, where no site-specific Hamilton geoacoustic data existed and the Rubano geoacoustic parameters were used. Since the three sites were separated by only a few kilometers, the assumption of using a single site-specific geoacoustic model over a large area of shallow water does not seem feasible from the results of this data set.