U.S. Ocean Sound Monitoring and Condition Reporting

Why are we monitoring ocean sound?

Ocean sound is critical for the survival of many marine animals because it is a primary means of communication, orientation and navigation, finding food, avoiding predators, and choosing mates. Many of the things people do offshore also introduce sound underwater. Therefore, we can use sound to track how people are using offshore spaces, just as we track marine animals. We can also track how human activities that produce underwater sounds interfere with animals' ability to hear prey, predators, and each other. U.S. national marine sanctuaries are home to many acoustically active marine animals and understanding their presence as well as the impacts of noise is a conservation priority.

Overview of NOAA ocean sound monitoring effort

NOAA sound monitoring programs provide important information about species presence, soundscape conditions, and long-term trends. NOAA's Office of National Marine Sanctuaries (ONMS) maintains a nationally coordinated underwater sound monitoring network across the National Marine Sanctuary System, known as ONMS Sound. ONMS Sound works with partners to monitor ONMS regions: Eastern, West Coast, and Pacific Islands. ONMS Sound monitoring sites record in strategic locations within sanctuary boundaries and prioritize maintaining previously established monitoring sites for understanding long-term trends. The NOAA Noise Reference Station Network (NRS) is a collaboration between the NOAA National Marine Fisheries Service (NMFS), ONMS, Pacific Marine Environmental Laboratory, and the National Park Service to collect consistent and comparable long-term acoustic data sets covering all major regions of U.S. waters. Recordings and standardized sound measurements for ONMS Sound and NRS datasets are available through the NOAA National Centers for Environmental Information's (NCEI) Passive Acoustic Archive. Explore the ONMS Sound ocean sound monitoring sites using the NCEI Passive Acoustic Data Map Viewer shown below. Start by filtering to see ONMS sites by using Monitoring Programs drop down on left panel. You can also add the ONMS boundaries using the layers tab.

NOAA underwater sound data available through NCEI Passive Acoustic Data Archive, summarized in these reports

Data summarized below are available through the NCEI Google Cloud Platform. ONMS projects are represented by the different color bars. The Sanctuary Soundscape Monitoring Project or SanctSound collected data from 2018-2022. Some sites continued beyond 2022 to become long-term monitoring sites for ONMS Sound. Noise Reference Station (NRS) data collection began in 2014.

Gantt chart showing time periods that U.S. sound data are stored in NOAA’s NCEI repository and presented in this report, labeled by monitoring site and color-coded by monitoring project. Time periods begin in 2014 and go through the present. Credit: Megan McKenna and Emma Beretta/CIRES and NOAA

Understanding ocean sound

Soundscapes are complex – representing a variety of sounds from different sources present at a given time and location, and influenced by the weather. Each sanctuary has unique soundscapes or combinations of sounds present at any given time. We can track soundscape conditions over time and across sites using standardized soundscape metrics. We can also use ocean sound data as indicators for different sources in a soundscape (e.g. whales or vessels).

Infographic of icons representing examples of different sound sources in the ocean. Image: Aline Design for NOAA

Sound can be described in a variety of different ways. Two key attributes of sound are intensity, "loudness", and frequency, "pitch". Other attributes describe how the sound occurred over time: was it a short burst of sound or a long-lasting hum? Our standard measurements of “sound levels” of sounds summarize all these attributes: intensity, frequency, and duration.

Intensity or “loudness” is measured in decibels and describes how much pressure the sound contains (the amplitude); a low decibel or quiet sound contains less amplitude than a high amplitude or loud sound. Frequency is measured in hertz and provides information about tones (pitches) that are contained in a sound. Image: Aline Design for NOAA

Ocean Sound Conditions

Soundscapes vary across years, seasons, and within a day. Differences are driven by shifts in wind and weather patterns, migration and behavior of animals, and patterns in human activities. To compare differences we track how sound levels change in different frequencies using standardized soundscape metrics. Seasonal and annual percentiles of all the data are used to see how daily values fall within ranges for a given monitoring location. The example graphic below shows how we visualize soundscape conditions within different seasonal categories.

Sound is measured in terms of frequency (pitch of the sound in Hertz) shown on the x-axis and intensity (how loud the sound is in decibels) shown on the y-axis. The colored lines represent seasonal categories, vertical lines are the start of a frequency range that continues over the shaded area that a sound source of interest can be heard, and the black lines bound the soundscape to expected range of intensity based on when only wind noise is present.

Seasonal median sound levels (sound intensity measured by mean-square pressure in microPascal per Hertz) across a range of frequencies (~10 to ~24,000 hertz) at a given monitoring site, with annual recording effort represented by a bar graph underneath. Each season is a different colored line. Solid black lines show modeled ambient sound levels from wind at 1 m/s (lower line) and 22.6 m/s (upper line) based on hydrophone depth. Frequency bands indicative of a biological or anthropogenic sound source of interest are highlighted in semi-transparent gray and labeled; peak frequency for dominant fish species are labeled with vertical dashed lines. Credit: Megan McKenna and Emma Beretta/CIRES and NOAA

Ocean Sound Indicators

Ocean sound indicators are resource management-relevant metrics derived from long-term monitoring of ocean sound. These indicators track the status and trend of habitat condition, species presence, human-use patterns, and management activities. There are many analytical methods used to generate ocean sound indicators. In some locations sound frequencies are dominated by a specific source and we can use this frequency (e.g. 125 Hz for vessel noise) to track conditions. Other methods detect specific sources of interest. For example, the National Marine Fisheries Service (NMFS) maintains analysis of presence of marine mammals from ocean sound monitoring data. Detecting fish sounds is another priority for ONMS and the graphic below is an example of how ocean sound data tracks the time of day when fish are producing sounds, an indicator of biologically important times.

Radial plots showing the proportion of sampled acoustic data containing detections of fish chorusing, summarized by hour of day, for bocaccio (Sebastes paucispinis), plainfin midshipman (Porichthys notatus), white seabass (Atractoscion nobilis), and two unknown fish species UF440 and UF310 at listening stations MB01 in Monterey Bay National Marine Sanctuary. Recording at MB01 spanned from November 2018 to August 2023. Daily chorusing activity for each fish species is the number of days with chorusing presence per number of days recorded. Credit: Emma Beretta/CIRES and NOAA

Frequent reporting on NOAA sound data from ONMS and NRS long-term monitoring sites helps to ensure the most recent information is available for sanctuaries. These updated web-based reports include the most recent results on ocean sound conditions. The reports aim to provide:
(1) a summary of available ocean sound monitoring data for the NOAA researchers and partners to review and evaluate seasonal and annual conditions;
(2) a communication tool to be able to show status and trends of ocean sound conditions and indicators relevant to each sanctuary and reigon;
(3) an overview of ocean sound indicators that are available for sanctuary condition tracking in Sanctuary Watch.

To explore results for a specific sanctuary, click on the sanctuary name shown on the left panel of this page.

What are we learning?

Collaborative partnerships help us gain key insights on sanctuary resources and conditions from ocean sound data by leveraging ecological and technological expertise. Here are a few recent examples:

Kim, E., Kok, A., Beretta, E., Donahue, E., Hatch, L., Joseph, J., Margolina, T., Oestreich, W., Peavey Reeves, L., Ryan, J., Zobell, V. M., & Baumann-Pickering, S. (2025). Fish chorusing patterns in California (USA) National Marine Sanctuaries. Fish chorusing patterns in California (USA) National Marine Sanctuaries. Marine Ecology Progress Series, 764, 135-159.

Zang, E., Lammers, M., Pack, A., and Hatch, L. (2024). Impulsive sounds produced by humpback whale surface active behavior recorded on acoustic tags and bottom‐moored recorders. Marine Mammal Science, 40(1), 302-308.

McKenna, M. F., Rowell, T. J., Margolina, T., Baumann-Pickering, S., Solsona-Berga, A., Adams, J. D., ... & Hatch, L. T. (2024). Understanding vessel noise across a network of marine protected areas. Environmental Monitoring and Assessment, 196(4), 369.

Madrigal, B. C., Kügler, A., Zang, E., Lammers, M., Hatch, L. T., and Pacini, A. F. (2024). Comparing the underwater soundscape of the Hawaiian Islands Humpback Whale National Marine Sanctuary and potential influences of the COVID-19 pandemic. Frontiers in Marine Science, 11, 1342454.

Kim, E. B., Frasier, K. E., McKenna, M. F., Kok, A., Peavey Reeves, L. E., Oestreich, W. K., ... & Baumann-Pickering, S. (2023). Soundscape learning: An automatic method for separating fish chorus in marine soundscapes. The Journal of the Acoustical Society of America, 153(3), 1710-1722.

Lammers, M.O., Goodwin B., Kügler, A., Zang, E.J., Harvey, M., Margolina, T., Martinez, J.A., Merkens, K. and Hatch, L.T. (2023). The occurrence of humpback whales across the Hawaiian archipelago revealed by fixed and mobile acoustic monitoring . Frontiers in Marine Science, 10:1083583.

McKenna, M. F., Baumann-Pickering, S., Kok, A. C., Oestreich, W. K., Adams, J. D., Barkowski, J., ... & Hatch, L. T. (2021). Advancing the interpretation of shallow water marine soundscapes. Frontiers in Marine Science, 8, 719258.

DeAngelis, A. I., Van Parijs, S. M., Barkowski, J., Baumann-Pickering, S., Burger, K., Davis, G. E., ... & Hatch, L. (2022). Exploring marine mammal presence across seven US national marine sanctuaries. Frontiers in Remote Sensing, 3, 970401.

ZoBell, V. M., Posdaljian, N., Lenssen, K. L., Wiggins, S. M., Hildebrand, J. A., Baumann-Pickering, S., & Frasier, K. E. (2025). Climatic and economic fluctuations revealed by decadal ocean soundscapes. Journal of the Acoustical Society of America, 157(6), 4233–4251.

Ryan, J. P., Joseph, J. E., Margolina, T., Hatch, L. T., Azzara, A., Reyes, A., Southall, B. L., DeVogelaere, A., Peavey Reeves, L. E., Zhang, Y., Cline, D. E., Jones, B., McGill, P., Baumann-Pickering, S., & Stimpert, A. K. (2021). Reduction of low-frequency vessel noise in Monterey Bay National Marine Sanctuary during the COVID-19 pandemic. Frontiers in Marine Science, 8, 656566.

Ryan, J. P., Oestreich, W. K., Benoit-Bird, K. J., Waluk, C. M., Rueda, C. A., Cline, D. E., & others. (2025). Audible changes in marine trophic ecology: Baleen whale song tracks foraging conditions in the eastern North Pacific. PLoS ONE, 20(2), e0318624

Hatch, L., McKenna, M., Burnham, R., Frasier, K., Gabriele, C., Hastings, S., Haver, S., Kunz, A., MacGillivray, A., Malinka, C., Morten, J., Peavey Reeves, L., Trounce, K., Vagle, S., Wood, J., & ZoBell, V. (2025). A call for comparable measurements of underwater radiated noise related to vessel speed reduction programs. Journal of the Acoustical Society of America Express Letters, 5(8), 087201.

Haver, S. M., Dziak, R. P., Hatch, L. T., Haxel, J., Kavanagh, C., Matsumoto, H., McKenna, M. F., Roche, L., Van Parijs, S. M., Wall, C. C., & Gedamke, J. (2025). Retrospective on decadal progress of the NOAA/NPS ocean noise reference station network. PeerJ, 13, e20382.

Kok, A. C. M., Soderstjerna, C., Kim, E. B., Joseph, J. E., Margolina, T., Peavey Reeves, L. E., Hatch, L. T., & Baumann-Pickering, S. (2026). Acoustic behavior and diversity of fish calling in the Channel Islands. Journal of the Acoustical Society of America Express Letters, 6(1), 011202.

Learn more about the diversity of ocean sounds at Discovery of Sound in the Sea.