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Insights, technical note, 4 min read, 2026-10-17

Marine piling under the 2024 NOAA thresholds

NOAA Fisheries replaced its 2018 marine mammal acoustic guidance in October 2024. Hearing groups were renamed and several injury thresholds moved, so models built on the 2018 tables can report the wrong zones.

Title
Marine piling under the 2024 NOAA thresholds
Doc no.
TN-606
Rev
P1
Discipline
UW HD
Date
2026-10-17
Status
Published
What this means for you

If your project involves piling at sea, a study built on the 2018 thresholds gives injury zones that are too small for seals and sea lions and too large for dolphins and porpoises. Check which version of the guidance was used.

Version 3.0 of the technical guidance renames permanent threshold shift onset as auditory injury onset. The former mid-frequency cetacean group becomes high-frequency, and the former high-frequency group becomes very-high-frequency.1 Thresholds are dual metric, peak sound pressure and weighted cumulative sound exposure, and the larger of the two resulting ranges applies.

Impulsive sources, auditory injury onset (2024) and PTS onset (2018). Peak: dB re 1 µPa. SEL: weighted, 24 h, dB re 1 µPa²s.
Group (2024)Group (2018)Peak 2018Peak 2024SEL 2018SEL 2024
LF cetaceansLF219222183183
HF cetaceansMF230230185193
VHF cetaceansHF202202155159
Phocid pinnipeds (PW)PW218223185183
Otariid pinnipeds (OW)OW232230203185

The largest change is the otariid cumulative threshold, which fell from 203 to 185 dB.1,2 For a given piling schedule, a lower threshold means a longer injury range for sea lions and fur seals. The phocid cumulative threshold fell by 2 dB, while the high- and very-high-frequency cetacean cumulative thresholds rose by 8 and 4 dB.

Piling noise injury and TTS ranges by hearing groupIllustrative concentric ranges around a pile for auditory injury and temporary threshold shift onset for low-, high- and very-high-frequency cetaceans and phocid and otariid pinnipeds, with a table of ranges in kilometres.PileLFHFVHFPWOWRange, kmGroupInjuryTTSLF0.93.6HF0.20.9VHF1.66.4PW0.62.4OW0.10.5Auditory injury onsetTTS onsetWeighted SEL24h thresholds,NOAA Fisheries 2024 (v3.0)012 kmIllustrative
How injury and TTS ranges are drawn for each hearing group around a piling location.Ranges illustrative; thresholds from NOAA Fisheries v3.0 (2024).

What changes for a project

Re-run the cumulative exposure model against the 2024 groups rather than relabelling 2018 outputs, because the group definitions themselves changed. In October 2026 NOAA also published a multi-species pile driving calculator and interim proxy values, which give a common starting point for screening.3

Note

Where a national regulator does not specify marine mammal criteria, state that NOAA v3.0 is used and why. Advisers will check the version first.

Notes and references

  1. NOAA Fisheries (2024). 2024 Update to: Technical Guidance for Assessing the Effects of Anthropogenic Sound on Marine Mammal Hearing (Version 3.0), NOAA Technical Memorandum NMFS-OPR-71, Table ES3. https://www.fisheries.noaa.gov/s3/2024-11/Tech_Memo-Guidance_-3.0-_OCT-2024-508_OPR1.pdf Back to text
  2. NOAA Fisheries (2023). Summary of Marine Mammal Protection Act Acoustic Thresholds, February 2023 (2018 guidance values). https://www.fisheries.noaa.gov/s3/2023-02/MMAcousticThresholds_secureFEB2023_OPR1.pdf Back to text
  3. NOAA Fisheries. Marine mammal acoustic technical guidance and other acoustic tools (page updated October 2026). https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance-other-acoustic-tools Back to text

Send the piling schedule and site location. We tell you which hearing groups and ranges the assessment needs.

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