For how crucial whales have been for humanity, from their harvest for meat and oil to their future use of saving the world from a space probe, humans knew very little about them until surprisingly recently. Most people, even in Herman Melville’s time, considered whales to be fish, and it wasn’t until humans went looking for submarines in the mid-1900s that we started to understand the complexities of their songs. And you don’t have to be a submarine pilot to listen now, either; all you need is something like these homemade hydraphones.

This project was done as part of a workshop in Indonesia, and it only takes a few hours to build. It’s based on a piezo microphone enclosed in a small case. A standard 3.5 mm audio cable runs into the enclosure and powers a preamp using a transistor and two resistors. With the piezo microphone and amplifier installed in this case, the case itself is waterproofed with a spray and allowed to dry. When doing this build in places where Plasti-Dip is available, it was found to be a more reliable and faster waterproofing method. Either way, with the waterproofing layer finished, it’s ready to toss into a body of water to listen for various sounds.

Some further instructions beyond construction demonstrate how to use these to capture stereo sounds, using two microphones connected to a stereo jack. The creators also took a setup connected to a Raspberry Pi offshore to a floating dock and installed a set permanently, streaming live audio wirelessly back to the mainland for easy listening, review, and analysis. There are other ways of interacting with the ocean using sound as well, like this project, which looks to open-source a sonar system.

Thanks to [deathbots] for the tip!