Decadal Decreases in the Frequency (Pitch) of Baleen Whale Vocalizations Blue whales are the largest living mammal species. Their long, slender bodies can reach lengths of 30.5 m (100 ft) and weigh up to 160 tons. Blue whales produce stereotyped calls, described as pulses, grunts, groans, and moans, which are typically in the 15-40 [...]

Earthquakes and other geologic events produce acoustic signals that can be measured and monitored on land and underwater. Seismic energy from submarine earthquakes is converted into acoustic energy at the seafloor-water boundary.  A Tertiary wave (or T-wave) is an acoustic signal associated with earthquakes. T-waves propagate efficiently in the ocean compared to seismic waves through [...]

Measuring and mitigating the potential impacts of vessel noise on endangered killer whales Underwater sound associated with commercial vessel traffic is one, recognized threat to the southern resident population of killer whales. Image credit: NOAA, NWFSC. Southern resident killer whales (SRKW) are an endangered marine mammal population found off the Pacific coasts of [...]

An engineer prepares to deploy a single airgun. The airgun will be suspended about 8 m below the water surface from the white float seen at the bottom of the image. Image courtesy of the National Science Foundation. An airgun is a tool used to examine layers of the seafloor and study the Earth’s [...]

Using Underwater Acoustics to Detect and Measure Global Ocean Methane Flux Close up imagery of methane hydrate. Scientists study methane hydrates as a potential natural gas source and for its potential role in releasing methane to the atmosphere during climate change events. Image courtesy of the NOAA Office of Ocean Exploration and Research. [...]

Hydrophone Provides Continuous, Live Stream of Deep Sea Sounds from Monterey Bay Location of the MARS hydrophone, on the Smooth Ridge, at the edge of Monterey Canyon, approximately 30 km (18 mi) from shore. Image credit: MBARI. The Monterey Accelerated Research System (MARS) cabled observatory, the first cabled oceanographic observatory on the U.S. [...]

An international team of experts have partnered on a “bold” conservation plan (VaquitaCPR; https://www.vaquitacpr.org) to prevent the most endangered marine mammal in the world, the vaquita porpoise (Phocoena sinus), from going extinct. The vaquita is only found in the upper portion of Mexico’s Gulf of California. Its population was estimated at 567 individuals in 1997, [...]

The National Marine Fisheries Service (NMFS) is the U.S. federal agency that is responsible for the stewardship of the nation’s ocean resources, including the management of the majority of marine mammals, such as whales, dolphins, porpoises, seals, and sea lions. The U.S. Fish and Wildlife Service (USFWS) has jurisdiction over walruses, polar bears, manatees, dugongs, and sea [...]

    Hot Topic Scientists Measure Ambient Noise Levels in One of the Deepest Parts of the Global Ocean The ocean is filled with sound. Sound levels in the ocean differ from location to location and change with time. Some sounds are present more or less everywhere in the ocean all of the time. Some [...]

Acoustic Tracking Technologies Shed Light on the Feeding Behavior of Great White Sharks (left) Specially modified REMUS (remote environmental monitoring unit) autonomous underwater vehicle (AUV) used to locate, follow, and record the behavior, habitat use, and feeding ecology of great white sharks off the coast of Mexico. Note the bite marks, scrapes, and scars [...]