Marine Mammal Acoustic Thresholds

NOAA Fisheries finalized its Technical Guidance for Assessing the Effects of Anthropogenic Noise on Marine Mammal Hearing in July of 2016. The Technical Guidance is a document that compiles, interprets, and synthesizes scientific literature to produce updated acoustic thresholds to assess how anthropogenic, or human-caused, sound affects the hearing of all marine mammals under NOAA Fisheries jurisdiction. The updated acoustic thresholds cover the onset of both temporary (TTS) and permanent hearing threshold shifts (PTS) for Level A, though not yet for level B. Acoustic thresholds refer to the levels of sound that, if exceeded, will likely result in temporary or permanent changes in marine mammal hearing sensitivity. Notably, the Technical Guidance's updated acoustic thresholds do not represent an entire impact assessment. Instead, they serve as one tool to help evaluate the effects of a proposed action on marine mammals and make findings required by various statutes.

NOAA Fisheries in-water

acoustic thresholds


PTS Onset

(Received Level)

Level A:

Hearing Groups




Cetaceans (LF)

PK: 219 dB

SELcum: 183 dB

SELcum: 199 dB


Cetaceans (MF)

PK: 230 dB

SELcum: 185 dB

SELcum: 198 dB


Cetaceans (HF)

PK: 202 dB

SELcum: 155 dB

SELcum: 173 dB

Phocid Pinnipeds (PW)

PK: 218 dB

SELcum: 185 dB

SELcum: 201 dB

Otariid Pinnipeds (OW)

PK: 232 dB

SELcum: 203 dB

SELcum: 219 dB


Criterion Definition


Level B

Behavioral disruption for impulsive noise

(e.g., impact pile driving)

160 dBrms


Level B

Behavioral disruption for continuous noise

(e.g., vibratory pile driving, drilling)

120* dBrms

Level A:

  • Dual Thresholds (impulsive): Use one resulting in large effect distance (isopleth)
  • SELcum thresholds incorporates weighting functions

Level B:

  • All decibels referenced to 1 micro Pascal (re: 1uPa).  Note all thresholds are based off root
    mean square (rms) levels.
  • *The 120 dB threshold may be slightly adjusted if background noise levels are at or above this level.

Technical Guidance

NOAA Fisheries current in-air acoustic thresholds:


Criterion Definition


Level A

PTS (injury) conservatively based on TTS

None established

Level B

Behavioral disruption for harbor seals

90 dBrms

Level B

Behavioral distruption for non-harbor seal pinnipeds

100 dBrms

All decibels referenced to 20 micro Pascals (re: 20uPa).  Note all thresholds are based off root mean square (rms) levels.