Hydrophones: how do they work?

‘While Orcasound started as a hydrophone network, it is rapidly evolving into an open source software and hardware project. Our goal is to build innovative technology that helps save endangered orcas, and to share it freely with other conservationists who want to save species that sing.

Our main project is a conservation tool called Orcasound (depicted below) -- a web app that makes it easy for humans to listen for whales in live audio data streams. From hydrophone to headphone, we inspire listeners to learn about orcas and underwater noise and give them opportunities to act. They can sign up to be notified when a live orca “concert” is detected, and then respond to conservation calls to action. They can become a citizen scientist: learning the sounds orcas make, and then pressing a button when they hear whales, a noise that could harm whales, or other interesting sounds. Thus, they help train machines to aid human listeners and issue even more notifications of sonic connections to the ocean.

As it has gained features, the Orcasound web app has spawned other related projects -- some of which are depicted above. Machines are beginning to listen in real-time alongside humans, trained from audio data tagged via the app and a suite of audio annotation projects. Acoustic detections at each Orcasound node are combining with sightings from visual networks to help map orca movements and study their habitat use. The same hydrophones deployed to listen for orcas can be used to monitor noise pollution from ships and boats.