Underwater Radiated Noise Levels along the California Coast for Participating Vessels in the 2025 Protecting Blue Whales and Blue Skies Program

Report

Title: Underwater Radiated Noise Levels along the California Coast for Participating Vessels in the 2025 Protecting Blue Whales and Blue Skies Program

Author:

Conti, M.; Reeves, L.; Haver, S.; Fraiser, K.; ZoBell, V.

Publication Date:

March 1, 2026

Document Number:

684

Pages:

1-21

Place Published:

La Jolla, CA

Affiliation

Scripps Institution of Oceanography, National Marine Sanctuary Foundation, NOAA Office of National Marine Sanctuaries, Oregon State University

Technology:

Wind Energy, Fixed Offshore Wind, Floating Offshore Wind

Stressor:

Noise

Receptor:

Marine Mammals, Cetaceans

Language:

English

Document Access

Website:

External Link

Attachment:

Access File

Citation

APA
BibTex
RIS

Conti, M.; Reeves, L.; Haver, S.; Fraiser, K.; ZoBell, V. (2026). Underwater Radiated Noise Levels along the California Coast for Participating Vessels in the 2025 Protecting Blue Whales and Blue Skies Program (Report No. 684). Report by Scripps Institution of Oceanography.

@techreport{Conti-2026-,
author = {Conti, M and Reeves, L and Haver, S and Fraiser, K and ZoBell, V},
title = {Underwater Radiated Noise Levels along the California Coast for Participating Vessels in the 2025 Protecting Blue Whales and Blue Skies Program},
institution = {Scripps Institution of Oceanography},
year = {2026},
month = {mar},
number = {684},
address = {La Jolla, CA},
url = {https://bluewhalesblueskies.org/wp-content/uploads/BWBS_2025_ZoBell_Report_final.pdf},
keywords = {Wind Energy, Fixed Offshore Wind, Floating Offshore Wind, Noise, Marine Mammals, Cetaceans},
}

Export Citation to BibTex

TY - RPRT
TI - Underwater Radiated Noise Levels along the California Coast for Participating Vessels in the 2025 Protecting Blue Whales and Blue Skies Program
AU - Conti, M
AU - Reeves, L
AU - Haver, S
AU - Fraiser, K
AU - ZoBell, V
AB - The Scripps Machine Listening Lab at Scripps Institution of Oceanography partnered with the Protecting Blue Whales and Blue Skies Program (BWBS) to analyze potential changes in underwater radiated noise (URN) levels of participating vessels for the 2025 incentive-based vessel speed reduction (VSR) initiative along the California coast. This report summarizes the study of sound metrics (source level and noise level) at five acoustic monitoring sites along the California coast, including the Santa Barbara Channel (Site B), Chumash Heritage National Marine Sanctuary (Site C), Morro Bay (Site WEA), Monterey Bay (Site MB) and Cordell Bank National Marine Sanctuary (Site CB). The VSR program was active during the 2025 season from January 1st-15th, and May 1st, 2025 through the end of the year and was open to all vessels 300 gross tons and larger that pass through the VSR zones.The specific goals of this study were to quantify vessel source levels (MSL) and ambient noise levels (NL) during transits of participating vessels at acoustic monitoring sites along the California coast; compare URN during the active 2025 VSR program with a 2016–2017 baseline when the program was inactive; compare NLs during the active 2025 VSR program with the inactive 2025 VSR period; and identify BWBS program-associated changes.The key results of this study are:Average broadband source levels were reduced during the VSR program active period compared to the 2016/2017 baseline at each site by 6.5 (Site B), 6.1 (Site C), 5.0 (Site MB), and 3.1 dB (Site CB).The overall program reduction in broadband source levels for 2025 compared to the 2016/2017 baseline was 5.2 dB. This equates to a 70% reduction in acoustic intensity (or 45% reduction in sound pressure amplitude).Average noise levels during transits were reduced by 3.8 (Site B), 4.8 (Site C), and 1.4 dB (Site CB) during the 2025 program active period compared to the same year inactive period. This results in an average NL reduction of 3.4 dB.
CY - La Jolla, CA
DA - 2026/03//
PY - 2026
SP - 1
EP - 21
PB - Scripps Institution of Oceanography
SN - 684
UR - https://bluewhalesblueskies.org/wp-content/uploads/BWBS_2025_ZoBell_Report_final.pdf
LA - English
KW - Wind Energy
KW - Fixed Offshore Wind
KW - Floating Offshore Wind
KW - Noise
KW - Marine Mammals
KW - Cetaceans
ER -

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Abstract

The Scripps Machine Listening Lab at Scripps Institution of Oceanography partnered with the Protecting Blue Whales and Blue Skies Program (BWBS) to analyze potential changes in underwater radiated noise (URN) levels of participating vessels for the 2025 incentive-based vessel speed reduction (VSR) initiative along the California coast. This report summarizes the study of sound metrics (source level and noise level) at five acoustic monitoring sites along the California coast, including the Santa Barbara Channel (Site B), Chumash Heritage National Marine Sanctuary (Site C), Morro Bay (Site WEA), Monterey Bay (Site MB) and Cordell Bank National Marine Sanctuary (Site CB). The VSR program was active during the 2025 season from January 1st-15th, and May 1st, 2025 through the end of the year and was open to all vessels 300 gross tons and larger that pass through the VSR zones.

The specific goals of this study were to quantify vessel source levels (MSL) and ambient noise levels (NL) during transits of participating vessels at acoustic monitoring sites along the California coast; compare URN during the active 2025 VSR program with a 2016–2017 baseline when the program was inactive; compare NLs during the active 2025 VSR program with the inactive 2025 VSR period; and identify BWBS program-associated changes.

The key results of this study are:

Average broadband source levels were reduced during the VSR program active period compared to the 2016/2017 baseline at each site by 6.5 (Site B), 6.1 (Site C), 5.0 (Site MB), and 3.1 dB (Site CB).
The overall program reduction in broadband source levels for 2025 compared to the 2016/2017 baseline was 5.2 dB. This equates to a 70% reduction in acoustic intensity (or 45% reduction in sound pressure amplitude).
Average noise levels during transits were reduced by 3.8 (Site B), 4.8 (Site C), and 1.4 dB (Site CB) during the 2025 program active period compared to the same year inactive period. This results in an average NL reduction of 3.4 dB.