Measuring vessel source level in shallow water using the smoothed semi-coherent image method
article
Standardizing the process for measuring underwater sound generated by ships in shallow waters is a complex challenge currently under development. Recent progress has enabled the development of analytical formulations to represent propagation conditions underwater using propagation loss (PL) approximations, which are employed to derive the source level (SL) from ship sound pressure level (SPL) measurements. Underwater radiated noise (URN) tests conducted in the SATURN project enabled a detailed evaluation of the seabed critical angle (SCA) method, recommended by an early draft of the ongoing ISO 17208-3 standard, identifying a general underestimation of SL above _500 Hz compared to measurements under equivalent operating conditions in deep water, as described by ISO 17208-1. This article presents an alternative smoothed semi-coherent image (SSCI) method for calculating PL (and hence SL) and assesses the method’s performance through analytical and empirical scenarios (including recordings of three different instrumentation deployment strategies at four distinct depths and four test distances). The SSCI method enhances accuracy over a broad frequency range while maintaining the general robustness, with a formulation that also seeks to preserve the simplicity of the SCA approach.
TNO Identifier
1008632
Source
Journal of the Acoustical Society of America, 157(3), pp. 1938-1954.
Pages
1938-1954
Files
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