Soundscapes
Abstract
The long-term goal of this project is to develop and validate a regional and global nowcast capability for ocean noise. The ambient noise field is a key part of the marine mammal habitat, and in turn can inform regulatory decisions by conservationists. Eventually this system will be coupled to global oceanographic models to provide hindcasts, nowcasts, and forecasts of the time-evolving soundscape. In terms of the types of sound sources found in the oceans, we will focus initially on commercial shipping and seismic exploration. As the research evolves, we will gradually expand the capability to include many other types of sources. The research has two principle thrusts: (1) the modeling of the soundscape, and (2) verification using datasets that have been collected around the Pacific and Atlantic Ocean basin. In terms of the modeling, we have begun with adiabatic normal modes (KRAKEN3D). In the adiabatic approximation, one assumes that the sound energy in any particular mode stays in that mode as the sound propagates radially from the source. This particular approach is extremely efficient. Longer term we will be including other models such as BELLHOP3D that can include mode coupling and 3D refractive effects. Regardless of the model type, we first pre-calculate the transmission loss (TL) for a grid of hypothetical sources covering the globe. We then compute the noise level (NL) by convolving this TL data with a source level (SL) density. This two-stage approach allows us to rapidly produce updated soundscapes as the SL density changes due to different source types or to temporal variations.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 30, 2013
- Accession Number
- ADA598506
Entities
People
- Laurel J. Henderson
- Michael B. Porter
Organizations
- HLS Research (United States)