Acoustics Module

The SEAT acoustics module evaluates the risk associated with sound pressure levels or sound exposure levels generated by MEC arrays. The SEAT module uses model results from Paracousti, which is an open-source underwater sound propagation simulator. Paracousti simulates sound wave propagation within realistic 3-D earth, atmosphere, and hydroacoustic models, and includes acoustic variability within medium density strata due to changes in topography, bathymetry, or voids in the subsurface. Paracousti model simulation are created for probabilistic sea states to determine influence of MECs on the marine noise environment and potential effects to marine species. The modules determines the percentage of time that an acoustics threshold will be exceeded spatially by combining: 1) a probability weighted acoustic field derived from individual Paracousti simulation NetCDF files; and 2) a species auditory threshold. SEAT can determine the likelihood of a species being impacted by using probability of occurrence or species density maps . Additionally, with the inclusion of a risk layer the impacts on specific regions of interest can be evaluated, such as breading grounds, vegetation.

Input

The input for the acoustic stress module is a set of NetCDF files containing data for scenarios with and without devices present from paracousti model output.

These include:

  • NetCDF files: model output with 1) baseline runs; 2) device present runs

  • *Receptor file (CSV): Includes species name, acoustic metric, threshold and density grid cell size

  • *Model Probability Condition file (CSV): Used to weight different run scenarios

  • *Risk layer file (GeoTIFF): Contains spatial classifications, used to evaluate the impact of the devices on the environment

  • *Spatial Probability/Density directory (directory): includes GeoTiffs or CSVs of species, density and corresponds to the probabilities file

*Optional input files

Input File Sources

SEAT is designed to read output from the Sandia paracousti model The user can provide input from alternative sources if the input are formatted correctly.

Default Sources

The MHkit friendly tools output acoustic data in NetCDF format. The NetCDF files contain variables that are based on the receptor input. These variables can include sound pressure level or sound exposure level variables. The variable name is specified in the receptor file.

Alternative Sources

If the user would like to use a different model, the user must ensure that the input files are formatted correctly within the NetCDF.

Coordinate variable names must be in the variable attributes such that:

  • xcor, ycor = netcdf_dataset.variables[variable].coordinates.split()

The coordinates units attribute must include “degrees” if the coordinates are lat/lon such that:

  • ‘degrees’ in ds.variables[<xcor variable>].units is True for lat/lon

Output

Note that if no baseline model files are provided, the baseline is assumed to be zero.

GeoTIFF raster files:

  • paracousti_stressor.tif : The probability weight difference between with devices and baseline models results.

  • paracousti_with_devices.tif: The probability weighted signal with devices

  • paracousti_without_devices.tif: The probability weighted signal without devices (baseline)

  • species_threshold_exceeded.tif : the percent of time the acoustic threshold was exceeded.

  • species_percent.tif : the threshold exceeded and weighted species percent.

  • species_density.tif : the threshold exceeded and weighted species density.

CSV files:

  • paracousti_stressor.csv

  • paracousti_with_devices.csv

  • paracousti_without_devices.csv

  • species_threshold_exceeded.csv

  • species_percent.csv

  • species_density.csv

Segmented by spatial classification when using the risk layer file:

  • paracousti_stressor_at_paracousti_risk_layer.csv

  • species_density_at_paracousti_risk_layer.csv

  • species_percent_at_paracousti_risk_layer.csv

Core Functions

Function

Description

calculate_acoustic_stressors()

Main function that loads data, performs calculations, and computes various metrics including acoustic differences and spatial variability of species auditory thresholds.

run_acoustic_stressor()

Creates GeoTIFFs and CSV files to visualize and quantify acoustic changes and spatial variability of species auditory thresholds.