Comparing methods for estimating the injury and behavioral disturbance radii from sound source characterization measurements

Abstract

It is a common practice for regulators to require project proponents to estimate the radius around a sound source where marine life could be injured or disturbed. Acoustic propagation modeling is normally required so that realistic radii are obtained that take into account the bathymetry, bottom properties, water column sound velocity profile, as well as source spectrum and directivity. Increasingly proponents are also asked to perform in-situ sound source characterization (SSC) measurements to verify the modeling predictions, including the spectrum and directivity of the sound source. During an SSC, sound levels are measured at increasing range from the source. In most cases, it is not possible to measure the sound levels at all ranges of interest, and therefore, the data must be interpolated or extrapolated to estimate the radii of the regulatory sound isopleths. This talk uses real-world data to identify the strengths and weaknesses of four methods of estimating the radii: (1) the practical spreading model; (2) linear interpolation; (3) linear regression with absorption; and (4) model-measured fits.