These recordings represent a growing collection of sounds within the ocean soundscape, as recorded offshore of Monterey Bay, California. They are part of a research and education project that employs a deep-sea observatory to continuously record sounds within and outside the range of human hearing. The ocean soundscape is a continuously changing mosaic of sounds that originate from living organisms (communication and foraging), natural processes (breaking waves, wind, rain, earthquakes), and human activities (shipping, construction, and resource extraction). Listening to sound in the sea is a rich exploration of the marine environment, which includes some of the ways in which human activities may influence marine life. We record ocean sound using a hydrophone, an underwater microphone. On July 28, 2015, a digital broadband hydrophone was connected to the MARS cabled observatory. Deployment went smoothly thanks to the ship’s crew and remotely operated vehicle (ROV) pilots. Shortly after the sound of the ROV faded from the MARS node as the ROV ascended to the ship, marine mammal vocalizations became clearly audible in the hydrophone recordings. This little hydrophone generates big data—about 24 terabytes in one year. Understanding this voluminous and dense data requires a variety of analysis methods – from automated recognition of vocalizations by marine mammals to long-term statistical descriptions of all sounds recorded. Automated methods that sift through the data to detect and classify vocalizations of different species are being developed and applied. This will allow examination of variations in the presence of different species in the Monterey Bay area, in relation to variations in the environment.
In addition to listening to recordings, we can also visually represent the soundscape using a spectrogram. A spectrogram quantifies sound energy as a function of frequency and time. Animation of spectrograms through time enables “soundscape visual browsing.”