The NOAA ship Bell M. Shimada has 3 hydrophones (underwater microphones) on its hull, and on the 2021 Joint U.S.-Canada Integrated Ecosystem and Pacific Hake Acoustic Trawl Survey we started a pilot project to record what comes from the hydrophones. Right now when we listen to the hydrophones, we mostly hear the rhythmic clicking of the echosounder (click link to play recording), kind of like a heartbeat. Click, pause, click, pause, click, and so on.
In the recordings you can also usually hear the sound of the propeller as well as sounds of water moving. And on some occasions you can hear other sounds, like the echolocation clicks of dolphins, which sound like a buzzing, and dolphin whistles, which sound a bit like a human whistle. We started recording from two of the hydrophones, and look forward to discovering what other sounds we can hear, how often, and where.
