Hydrophone in Monterey Bay Provides Live Stream of Ocean Sounds
Starting this week, anyone can eavesdrop on sounds in the deep sea via a continuous streaming YouTube video that carries live sound from 900 m (3,000 ft.) below the surface of Monterey Bay. The sounds on the stream come from an underwater microphone (hydrophone) that the Monterey Bay Aquarium Research Institute (MBARI) placed on the seafloor in 2015. The hydrophone is located about 30 km (18 mi.) from shore, just west of Monterey Bay. It is attached to the Monterey Accelerated Research System (MARS) undersea cabled observatory, which carries data from the hydrophone back to shore.
Although the MARS hydrophone is located on the deep seafloor, most of the sounds it picks up are from animals and activities higher up in the water or even at the sea surface. For example, it is common for the hydrophone to pick up the calls of sea lions, dolphins and other near-surface animals, as well as the sounds of rain, waves and wind blowing over the sea surface.
High-pitched sounds, such as dolphin clicks, do not travel very far through the water, so if these sounds show up in the stream they are probably being generated within a few km of the hydrophone. However, the low-pitched sounds of ship engines can travel dozens of km, and some whale calls may come from animals hundreds of km from Monterey Bay.
The MARS hydrophone can capture sounds both above and below the range of human hearing. The live stream does not carry high-pitched sounds above human hearing, but it does include very low sounds such as those produced by some whales. Listeners can hear these sounds if they have good headphones or subwoofer speakers.
In addition to hearing sounds from the hydrophone, listeners can also see the sounds in the form of a spectrogram that scrolls across the screen of the YouTube video. There is a 30-min. delay for computer processing and archiving between the time when the sounds are captured by the hydrophone and the time that they show up on the screen.
To help listeners explore the variety of sounds from the hydrophone, the MBARI team also prepared an online listening room web page. Recordings on this web page help visitors learn about the calls made by different types of whales and dolphins, as well as natural processes such as rain and earthquakes.
For researchers and others who would like to explore sounds previously detected by the hydrophone, the MBARI team created a web page where visitors can browse through two and one half years of spectrograms, located here, which allows searches by sound type, day or month.
MBARI researchers are collaborating with scientists at the Monterey Bay National Marine Sanctuary, the U.S. Naval Postgraduate School, Moss Landing Marine Laboratories, the University of California at Santa Cruz, the Scripps Institution of Oceanography, and others to analyze the sounds from the MARS hydrophone. Their work is revealing new information about the behavior of whales and other marine mammals along the Central California coast.