SUPPLEMENTARY INFORMATION:

NOAA has developed draft guidance for assessing the effects of anthropogenic sound on the hearing of marine mammal species under NOAA's jurisdiction ( i.e., whales, dolphins, porpoises, seals and sea lions). Specifically, the guidance identifies the received levels, or thresholds, above which individual marine mammals are predicted to experience changes in their hearing sensitivity (either temporary or permanent) for all underwater anthropogenic sound sources. This guidance is intended to be used by NOAA analysts and managers and other relevant user groups and stakeholders, including other federal agencies, when seeking to determine whether and how their activities are expected to result in particular types of impacts to marine mammals via acoustic exposure. The document outlines NOAA's updated acoustic threshold level, describes in detail how the thresholds were developed, and explains how they will be updated in the future. NOAA published a Federal Register Notice on December 27, 2013, announcing the availability of the draft guidance and a 30-day public comment period (78 FR 78822), which was extended another 45 days based upon public request on January 29, 2014 (79 FR 4672). Please refer to these Federal Register Notices for additional background about the draft guidance.

While NOAA was in the process of evaluating and addressing public comments, the U.S. Navy updated its methodology for the development of marine mammal auditory weighting functions and acoustic threshold levels. NOAA evaluated the proposed methodology and preliminarily determined that it reflects the best available science. Accordingly, we have incorporated it into our draft guidance. NOAA also re-evaluated its methods for defining threshold usage for sources characterized as “impulsive” or “non-impulsive” based on comments received during the initial public comment period. As a result, NOAA is now soliciting public comment, via this second public comment period, on this revised version of the draft guidance that incorporates these changes.

Updated sections can be found in the following locations: (1) A summary of the updated draft acoustic threshold levels and marine mammal auditory weighting functions is in the main body of the document, with additional details provided in Appendix A (Navy Technical Report); (2) NOAA's proposed methodology for defining threshold usage for sources characterized as “impulsive” or “non-impulsive” is in Section 2.3.1 of the main document, with additional details in Appendix C; (3) a new appendix identifying research recommendations and data gaps in response to comments submitted during the initial public comment period is Appendix D; and a new appendix providing optional alternative methodology for user groups unable to apply the guidance's more complex acoustic threshold levels and auditory weighting functions is Appendix E.

Before the guidance is finalized, NOAA will address substantive public comments received from the initial public comment period, as well as from this second public comment period. Therefore, NOAA encourages the public to currently focus comments on the revised and new sections of the document. We are particularly interested in identification of any additional datasets for inclusion in the assessment, comments on our proposed methodology for transitioning from “impulsive” to “non-impulsive” acoustic threshold levels, and evaluation of the methodology associated with updated marine mammal auditory weighting functions and acoustic thresholds.

The guidance is classified as a Highly Influential Scientific Assessment by the Office of Management and Budget. As such, independent peer review is required prior to broad public dissemination by the Federal Government. NOAA recently conducted two independent peer reviews in association with the revised draft guidance (in addition to the peer review on the first draft of the guidance). Details of both peer reviews can be found within the draft guidance and at the following Web site: http://www.nmfs.noaa.gov/​pr/​acoustics/​.