Low frequency acoustics propagation and noise and reverberation modeling
Abstract
This initiative will support research in support of improving the understanding of underwater acoustic propagation, with particular emphasis on two areas of relevance to the US Navy. The three topics of focus for FY22 will be Very Low Frequency (VLF) propagation, low frequency (LF) ambient noise and reverberation modeling using the very efficient Energy Flux (EFLUX) model. VLF work will be focused on propagation of sound in the open ocean at and below 35 Hz. This includes 1 Hz and what is called high-frequency seismology. Recent exciting developments for conducting passive travel time thermometry from stable, stationary earthquakes using differential travel time, rather than absolute, (work by Wu, Calais and his colleagues as well as Evers and his colleagues) presents the opportunity to find long term acoustic datasets and evaluate the oceanographic change during the past 15 years. Noise levels at 1 Hz have been shown to be correlated with El-Nino. The mechanism for this correlation is not well understood. The Energy Flux model (EFLUX), developed by Charles Holland, following on the work of Weston and Chris Harrison, has been coded in c by Dr. Heaney and has been accepted for OAML approval. NAVAIR is actively pursuing integrating EFLUX into ASPECT and is developing a noise model with EFLUX for the development DDVLA (digital DIFAR vertical line array sonobuoy). Basic research needs to be conducted into the impact of separating the vertical and horizontal components and incorporating a truly bi-static scattering kernel. The EFLUX model is truly adiabatic in nature – energy cannot be transferred from one ray bundle (launch angle) to another. This means that energy cannot leak from ducts, it cannot be affected by surface or bottom roughness and cannot change angles significantly from changing bathymetry. Dr. Heaney proposes to develop a transport theory model, which would compute the “mode-conversion” form one ray bundle to each of the others as a function of the local environment and its changes
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 13, 2022
- Source ID
- N000142212584
Entities
People
- Kevin Heaney
Organizations
- Office of Naval Research
- United States Navy