Research Technical Report

Characteristics of Sounds Emitted During High-Resolution Marine Geophysical Surveys

Naval Undersea Warfare Center Division-Newport, Technical Report 12,203

INTRODUCTION

Marine geophysical acoustic survey systems are critical to the mission of several federal agencies including the Bureau of Ocean Energy Management (BOEM), U.S. Geological Survey (USGS), U.S. Army Corps of Engineers (USACE), National Oceanic and Atmospheric Administration (NOAA), U.S. Navy (USN), and the National Science Foundation (NSF). Geophysical survey systems are used by these agencies (and commercial interests) to support exploration and development on the outer continental shelf (OCS) including marine transportation, oil and gas, marine mineral, and renewable energy projects. In particular, geophysical surveys support infrastructure siting, sand resource delineation, geomorphic characterization, environmental monitoring, archaeological resource identification, and mapping of shallow hazards. The USGS Coastal and Marine Geology Program (CMGP), USACE Civil Works, and NOAA National Ocean Service (NOS) Office of Coast Surveys use the same technology for similar purposes on the shallower inner continental shelf (ICS).

Given the significant scientific questions and uncertainty about the potential impacts associated with noise in the marine environment, an increasing number of regulatory requirements and precautionary mitigation strategies are being applied to lower-energy geophysical surveys including those of short duration and limited geographic footprint. The BOEM is working to ensure that environmental mitigation requirements are scientifically supported, cost effective, operationally feasible, and impact reducing. BOEM is advancing this objective by characterizing the acoustic energy radiated by geophysical survey systems used on the continental shelf, and other shallow bodies of water under U.S. jurisdiction. Thus, characterizing the acoustic fields radiated by marine geophysical acoustic survey systems is a critical first step to understanding the potential for these surveys to impact marine ecosystems.

This report presents results of work performed under interagency agreements (IAs) between BOEM, USGS and the Naval Undersea Warfare Center Division Newport (NUWCDIVNPT) of the Naval Sea Systems Command (NAVSEA). The overall objective of this study was to acquire and analyze calibrated acoustic source data for a number of commonly used marine geophysical survey systems as required to support subsequent sound source verification of these systems in situ by future BOEM-USGS studies. This objective was satisfied by performing a series of acoustic measurements in an acoustic tank and in open bodies of water using methods and standards traceable to U.S. standards maintained by the Underwater Sound Reference Division (USRD).