Sanctuary Soundscape Monitoring Project (SanctSound)

The National Oceanic and Atmospheric Administration (NOAA) and the U.S. Navy are working to better understand underwater sound within the  National Marine Sanctuary System . Since fall 2018, the agencies have been working with a number of scientific partners to study sound within seven national marine sanctuaries and one marine national monument, in waters off Hawai’i and the U.S. East and West Coasts. Standardized measurements are being used to identify sounds produced by marine animals, physical processes (e.g., wind and waves), and human activities, and comparisons are being made across these 30 nationally-distributed locations. Information from this project will be available to the public to download and explore starting in 2022. In the meantime, this story map invites you to take a tour of the places where this work is underway and introduces you to some of the questions this project seeks to answer in order to better understand and protect these special underwater places.

Ever tried to explain to a friend how noisy it was in a new, bustling restaurant? Or how silent it was during a hike in the wilderness? You often find yourself making comparisons to other places you’ve been in order to make your point: “it was louder than the library, but quieter than the coffee shop down the street.” But how do we ensure that such comparisons made across marine protected areas hundreds of miles away from each other are based on accurate information about what the acoustic conditions are really like in these different places?

The goal of the SanctSound project is to understand how sound varies in the ocean by collecting the same information in sanctuaries around the United States. To do this, 30 locations within seven national marine sanctuaries and one marine national monument were selected to listen to the ocean, as continuously as possible, over a period of three years.

At each of these locations, sound is being recorded using an underwater microphone (also known as a hydrophone) placed near the seafloor. Periodically we retrieve the instruments to download the recordings and refresh the batteries. At shallower locations like those in Gray’s Reef National Marine Sanctuary off the coast of Georgia, this equipment is placed and retrieved by divers. At deeper locations such as those in Monterey Bay National Marine Sanctuary, gear is deployed over the side of the sanctuary’s research boats and allowed to sink to the seafloor using an anchored mooring line. Also attached to each mooring line is a release system, placed between the recording equipment and anchor, which is used to remotely release the gear for recovery. After release, the recording equipment rises to the surface and gets picked up by scientists on the research vessel. Both listening station maintenance methods enable continuous recordings at stationary locations.

Ever tried to negotiate where to sit at a concert with a friend who thinks it’s much louder up front than you do? Or wondered how cars are rated loud or quiet? What was it about what you heard, or didn’t hear, that you noticed? Common measurement methods are key to providing a baseline for comparing the acoustic attributes of different places before taking into account differences in how we each experience them as individuals.

SanctSound collects a large amount of information via continuous underwater recordings. In fact, by its end in spring 2022, the project will have collected close to 300 terabytes of data. For context, approximately 500 hours of film can fit in one terabyte! A primary goal of SanctSound is to allow people to easily explore and access much of that data, and to showcase the types of information that sound can provide to help us understand and protect our oceans and its inhabitants. SanctSound data are archived and downloadable from the  NOAA National Centers for Environmental Information  (NCEI).

For example, recordings collected in 2019 at Olympic Coast National Marine Sanctuary SanctSound listening stations are currently accessible at NCEI. One tool for visualizing sound data and changes in the soundscape is the spectrogram. A spectrogram uses color to show the intensity (or loudness) of sound at various frequencies (or pitches) over time. Not only can you see whether sound is more or less intense at different frequencies, for example, 100 Hertz vs 1,000 Hertz, across time at one location, but you can also compare two spectrograms to see how intensity levels differ by location. The spectrograms below are from two different recording locations in Olympic Coast National Marine Sanctuary over the same time period (August 20 - September 4, 2019). You can see that lower pitch sounds from vessel noise are the loudest (warmer colors) contributors to the soundscape at both locations, but that vessel noise is constant in the location shown on top versus periodic in the location shown on bottom. This makes sense, as the top location (OC-02) is the listening station in the middle of international shipping lanes approaching and exiting Puget Sound and the ports of Seattle and Vancouver, while the bottom location (OC-04) is the listening station further south that experiences intermittent traffic from smaller vessels, like fishing boats operating seasonally.

Ever traveled to a new city and noticed how different it sounded from home? Sometimes you know immediately what is making a sound because it is relatively common and sounds about the same wherever you go (e.g., train passing by, airplanes taking off, truck backing up). Other sounds might be harder to figure out: What bird makes that call? Is that a baby crying in the distance?

SanctSound listening stations hear a variety of sounds including physical processes, animals, and human activities. Reef-dwelling invertebrates like snapping shrimp, fish, and whales, vessels big and small, fishing activities, and sonars used in military training are a few of the expected and relatively well-characterized sources of sound the project is hearing.

Only a few types of sounds are present at all of the project’s recording locations. These include the underwater sounds made by vessels both big and small. 

Some sounds were present over many locations, including sounds made by  snapping shrimp , which are heard in Gray’s Reef, Florida Keys, Channel Islands, and Hawaiian Islands Humpback national marine sanctuaries.

Still other sounds were present in only one or a few locations, like  humpback whales  singing in their Hawaiian Islands Humpback Whale National Marine Sanctuary breeding grounds.

Sounds produced by animals often peak during specific periods of the day, and during specific months or seasons based on the roles the sound plays in the animals’ reproductive, feeding or migratory activity. We can graph the number of times a certain sound is recorded each month to look for times of year when that sound is a more or less important component of the sanctuary soundscape. For example, how often we hear  black groupers  calling at a listening station in Florida Keys National Marine Sanctuary.

Ever been in a quiet library and noticed that you can hear someone clicking their pen from across the room? Ever notice you can talk comfortably with a friend in an empty coffee shop but have to pull your stools closer when the room fills up?

Each of the 30 recording locations selected for this study are recording sounds over different ranges based on the different environments in which they are placed. When you listen in a specific place, your ability to hear different sounds is dependent on the sound itself and the path the sound travels from the source to you – or in this case, the hydrophone. Important qualities for the sound include how loud it is and the frequencies, or tones, it contains. Louder and lower pitch sounds can generally be heard farther away than quieter and higher pitch sounds. But the path that sound wave takes through the water, known as a sound’s “propagation,” is influenced by numerous factors like the depth of the source in the water column, the depth of the seafloor, whether the seafloor is hard or soft, bumpy or flat, and properties of the water itself (e.g., salinity, temperature, density).

When we compare and explore sound recordings made at different recording locations, it’s important to know if the hydrophone at a location is recording sounds from a very small area near the hydrophone or a much larger surrounding area. To estimate the “listening range” over which a hydrophone can hear specific sounds, we used mathematical models of sound wave propagation combined with the known characteristics of the environment around each location (e.g., depth, composition of seabed) and the known characteristics of several different sounds of interest (the intensity and main frequency content of boats, fish calls, and whale song). The maps below show the estimated distances over which a sound with the same characteristics can be transmitted, on the left when it’s made in the deeper waters of Monterey Bay National Marine Sanctuary off the U.S. West Coast, and on the right when it’s made in the shallow waters of Gray’s Reef National Marine Sanctuary off the U.S. East Coast.

Ever tried to identify something by touching it while your eyes were blindfolded? Or tried to enjoy food with a congested nose? Like most animals, we gather information from a variety of sources to make sense of the world around us. Rarely do we experience input from any one source in isolation. Similarly, sound is one of many ways that marine animals experience their environments, and one of many ways that we can study those environments. We gain the most understanding when we add what we hear to other ways of understanding an ecosystem.

 SanctSound  combines sound data with the other types of observations we make throughout the  National Marine Sanctuary System in order to better understand and protect these special places. Long-term, standardized underwater sound recordings can greatly enhance what we learn from other measurement systems that aim to characterize the diversity and health of marine environments, including satellites, scuba surveys, autonomous underwater vehicles, and oceanographic research cruises. 

Read more about what we’re learning in these short stories:

 SanctSound: Listening to the (Not So) Silent World 

 Eavesdropping On Whales : How Acoustic Surveys are Revolutionizing Humpback Whale Monitoring in Hawai’i

 Listening to the Ocean in the Time of COVID-19 

 One Fish, Two Fish, Quiet Fish, Loud Fish 

 Understanding Underwater Noise in Monterey Bay National Marine Sanctuary 

 Estimating Fishing and Diving Use at Gray's Reef by Listening to Boats 

SanctSound is a nationally coordinated project co-led by NOAA’s Office of National Marine Sanctuaries and the U.S. Navy, and represents collaboration among a large number of people with expertise ranging from field operations to analysis to data management to communications.