N24A-T020 TITLE: Biological Noise Modeling for Active and Passive Sonar System Performance Predictions

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Advanced Computing and Software

OBJECTIVE: Develop a biologic noise model compatible with Navy standard acoustic propagation packages (CASS and RAM) and highlight existing available and/or lacking biologic diversity density databases. The model should be applicable for both active and passive sonar performance predictions by including both the biologic vocalizations and scattering properties as a function of frequency.

DESCRIPTION: The Department of the Navy (DON) seeks to develop and demonstrate new reliable and computationally efficient biologic noise models for use within sonar performance prediction modeling packages such as CASS-GRAB or RAM-PE. Underwater acoustic energy is often dominated by shipping noise (low frequencies) and wind-wave noise (midrange frequencies (MF)). There are existing noise models and techniques for both of these predominate noise sources. However, in some geographical areas, biologics can be the limiting noise source. This can occur in passive sensing when produce vocalizations in the frequency bands of interest (LF and MF) which can be louder than the other noise sources. For active sonar, scattering from biologics can also cause significant clutter to sonar screens and impact the Pd/Pfa for the system. This STTR topic aims to identify existing, applicable or available biologic diversity density databases, to propose any new data bases that should be considered, select a processing technique in order to determine the statistical representation of noise contribution from biologics vocalization, integrate the developed model into a DON tactical decision aid (TDA), and ultimately have the model accredited for the Oceanographic and Atmospheric Master Library (OAML).

PHASE I: Develop the initial model architecture, conceptual design, and the algorithms necessary to demonstrate a Technical Readiness Level (TRL) of 3. This should include:

• Identification of applicable biologic databases and proposal of any new databases that should be considered

• Selection of processing technique to determine statistical representation of noise contribution from biologics vocalizations to the levels produced, spatial location of sources, and time dependencies (such as diurnal patterns)

• Case example for a representative sonar system

Put forward a model development and validation plan for subsequent phases of the effort.

PHASE II: Further mature biologic noise model based on the Phase I design(s) validated to TRL 5 (Phase II Base), TRL 6 (Phase II Option, if exercised). Validation criteria include required computational load, accuracy, processing time, special and temporal resolution, and compatibility with Navy TDAs. Upon completion of Phase II, the developed model and a technical report outlining function and validation/verification of performance should be delivered to the Department of the Navy.

PHASE III DUAL USE APPLICATIONS: Align Phase III efforts with the program of record to integrate the results of the Phase II work. This includes the productionization of source code, incorporation of algorithms to Navy systems (where feasible), and adjusting model requirements based on needs of the operational environment.

Dual-use applications include coordination with other governmental partners for oceanographic monitoring and data collection (such as National Oceanic and Atmospheric Association (NOAA)) and university partners using data for pedagogical and/or research purposes.

REFERENCES:

1. Hildebrand, John A. et al. "An empirical model for wind-generated ocean noise." The Journal of the Acoustical Society of America 149, 4516, 2021. https://doi.org/10.1121/10.0005430
2. Collins, Michael D. "Users Guide for RAM Versions 1.0 and 1.0p." NRL
3. Keenan, R. "An Introduction to GRAB Eigenrays and CASS Reverberation and Signal Excess." OCEANS 2000 MTS/IEEE Conference and Exhibition. Conference Proceedings (Cat. No.00CH37158), Providence, RI, USA, 2000, pp. 1065-1070 vol.2.
4. Farcas, Adrian et al. "Validated shipping noise maps of the Northeast Atlantic." Science of The Total Environment Volume 735, 15 September 2020, 139509. https://doi.org/10.1016/j.scitotenv.2020.139509

KEYWORDS: Ocean Acoustics, Marine Biology, Oceanographic Models, Modeling, Tactical Decision Aids, SONAR Systems

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