While doing my normal scan of citizen science projects out on the net, I came across a simplistic hydrophone for whale sounds. While I know there are professional mic systems for this type of work, I had no idea the DIY community had been working on solutions as well. Needless to say, I ventured down the rabbit hole of all things dealing with underwater microphones. Projects ranged from a solder-less variety for educational purposes to an inexpensive recording style device. However, the one that won my heart was designed by Philip Cox for the Seaperch platform. Philip is part of the Utah Underwater Robotics (UUR) program, matching college students and volunteer teachers with middle school students for STEM learning.
This hydrophone uses an Arduino and Processing for a visual display, which is what makes this device so fun. A simple electret microphone is placed in a recycled film canister filled with mineral oil. That sounds crazy if you don’t know science, but Phil explains it all in his report.
First, it allows the waves to propagate more continuously through liquids, rather than traveling through air. Second it helps prevent leakage of water into the cavity, causing damage to the microphone. Finally, it also helps with lowering the buoyancy of the microphone while under water.
With a bit of sealant and electrical tape, it’s ready to go. One of the nice touches here is the connectors that Phil adds, making things more modular. The film canister is also a cool find, although they will get harder to locate as everything has gone digital; perhaps a small Tupperware is next. As with any project there are other things that can be explored. The tutorial does not mention whether the Processing or Arduino code addresses the scale of the sound. For instance, an LED could change different colors based on whether a sound is from a whale vs. a dolphin. In fact, the audio could be used to generate some interesting artwork using the Processing. There are so many fun possibilities for this little gadget and I’m glad to have made the discovery. If you want to give this project a go, we have an Electret Microphone Amplifier for you. You can also check out a project that uses this mic—the Adafruit Microphone Amplifier Breakout. See how the mic is used here with a bi-color LED matrix to visualize the sounds. Who knew mics could be so much fun?