To those of us on land, the world underneath the oceans seems quiet and serene. But scientists who study ocean acoustics will tell you it is anything but tranquil underwater. Our oceans are home to a cacophony of sounds – from the songs of marine mammals to the cracking of icebergs to the rumbling of earthquakes to the roar of ships.

In this episode, Bob Dziak, head of NOAA’s acoustics program, describes the sounds scientists study with their underwater microphones, including the noises they’ve heard at the deepest part of the ocean in the Mariana Trench and a mysterious “bloop, and how they use that information to understand natural processes and the impact from human activities.

This episode was produced by Nanci Bompey and mixed by Kayla Surrey.