Interim Sound Threshold Guidance

NOAA is developing comprehensive guidance on sound characteristics likely to cause injury and behavioral disruption in the context of the Marine Mammal Protection Act (MMPA), Endangered Species Act (ESA) and other statutes. Until formal guidance is available, NOAA Fisheries uses conservative thresholds of received sound pressure levels from broad band sounds that may cause behavioral disturbance and injury. These conservative thresholds are applied in MMPA permits and Endangered Species Act Section 7 consultations for marine mammals to evaluate the potential for sound effects. The criterion levels specified below are specific to the levels of harassment permitted under the MMPA.

NOAA Fisheries current in-water acoustic thresholds
(excluding tactical sonar and explosives):
CriterionCriterion DefinitionThreshold
Level APTS (injury) conservatively based on TTS190 dBrms for pinnipeds
180 dBrms for cetaceans
Level BBehavioral disruption for impulsive noise (e.g., impact pile driving)160 dBrms
Level BBehavioral disruption for non-pulse noise (e.g., vibratory pile driving, drilling)120* dBrms

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.

NOAA Fisheries current in-air acoustic thresholds:
CriterionCriterion DefinitionThreshold
Level APTS (injury) conservatively based on TTSNone established
Level BBehavioral disruption for harbor seals90 dBrms
Level BBehavioral distruption for non-harbor seal pinnipeds100 dBrms

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