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NOAA's Marine Mammal Acoustic Guidance

Status of NOAA's Guidance for Assessing the Effects of Anthropogenic Sound on Marine Mammals

The National Oceanic and Atmospheric Administration (NOAA) is developing acoustic guidance for assessing the effects of anthropogenic sound on marine mammal species [pdf] under our jurisdiction.

Specifically, the Guidance provides acoustic threshold levels for onset of permanent threshold shift (PTS) and temporary threshold shifts (TTS) for all sound sources. It is intended to be used by NOAA analysts/managers and other relevant user groups/stakeholders, including other federal agencies to better predict a marine mammal’s response to sound exposure in a manner that has the potential to trigger certain requirements under one or more of NOAA’s statutes (e.g., MMPA, ESA, and National Marine Sanctuaries Act). Due to the complexity and variability of marine mammal behavioral responses, NOAA will continue to work over the next year on developing guidance regarding the effects of anthropogenic sound on marine mammal behavior.

To develop these acoustic threshold levels, NOAA has compiled, interpreted, and synthesized best available information currently available on the effects of anthropogenic sound on marine mammals, as well as developed a method for updating these levels through a systematic, transparent process. The document outlines NOAA's updated acoustic threshold levels and describes in detail how the thresholds were developed and how they will be updated in the future.

Where are we in the Process?
The process to finalize the guidelines includes the following steps:

  1. NOAA internal review
  2. External peer review
    » Initial Peer Review Report [pdf]
  3. Public comment
  4. Finalize and release guidance

NOAA's initial draft acoustic Guidance [pdf] has undergone an internal review, an external peer review, and received informal input from key federal partners. The external peer review, which was completed September 2013, focused on the scientific and technical studies used in the analysis for the development of proposed onset PTS and TTS acoustic threshold levels.

Recent update (2015)

For their Phase 3 Acoustic Effects Analysis, the U.S. Navy recently (January 2015) provided NOAA with a technical paper describing their proposed methodology for updating auditory weighting functions and subsequent numeric thresholds for predicting auditory effects (TTS/PTS thresholds) on marine animals exposed to active sonars and other active acoustic sources utilized during Navy training and testing activities.

Upon evaluation, NOAA preliminarily determined that the Navy's proposed methodology reflects the best available science and are working to incorporate it into our Acoustic Guidance before it becomes final. Before doing so, we have commissioned an independent peer review of the Navy's technical paper (i.e. second peer review). 

Additionally, NOAA has re-evaluated its methods for defining threshold usage for sources characterized as impulsive or non-impulsive using comments from the initial public comment period. This proposed methodology is also undergoing a separate independent peer review (i.e. third peer review) before we incorporate it into our guidance.

Following these peer reviews, we will hold a second public comment period. 

Consistent with our Draft Guidance’s finalization procedure, once the peer review and public comment period processes are complete, NOAA will evaluate how to best incorporate the proposed methodologies into our Final Guidance.

More information about these additional peer reviews


Comments on the initial Draft Guidance

The comment period on the initial draft guidance opened in December 2013 (78 FR 78822) and closed on March 13, 2014 (79 FR 4672). Comments received are available on

Following the additional peer reviews, there will be another public comment period announced through a Federal Register Notice.

Public meeting/ webinar

NOAA Fisheries held a public meeting to inform interested parties and solicit comments on the proposed acoustic guidance. The meeting was held on January 14, 2014, in the NOAA Science Center in Silver Spring, MD. A transcript from the meeting is now available.

Meeting materials:

Second Public Comment Period

There will be a second public comment period announced after the Guidance has undergone the additional peer reviews. NOAA is in the process of evaluating the need for an additional public meeting/webinar associated with the upcoming second public comment period, standby for an announcement with more information.

Once the comments from all the peer reviews and public comment periods are addressed, NOAA will finalize and release the acoustic guidelines for onset PTS and TTS.

Frequently Asked Questions Regarding NOAA's Acoustic Guidance are also available (updated Apr 2015).

For more information, please contact:

Amy R. Scholik-Schlomer
NMFS Protected Resources Acoustic Coordinator
1315 East West Highway
Silver Spring, MD 20910

Updated: April 17, 2015