I’m Andrew Thaler and I build weird things.
Last month, while traveling to Kuching for Make for the Planet Borneo, I had an idea for the next strange ocean education project: what if we could use bone-conducting headphones to “see” the world like a dolphin might through echolocation? Spoilers: You can.
Bone-conducting headphones use speakers or tiny motors to send vibrations directly into the bone of you skull. This works surprisingly well for listening to music or amplifying voices without obstructing the ear. The first time you try it, it’s an odd experience. Though you hear the sound just fine, it doesn’t feel like it’s coming through your ears. Bone conduction has been used for a while now in hearing aids as well as military- and industrial-grade communications systems, but the tech has recently cropped up in sports headphones for people who want to listen to music and podcasts on a run without tuning out the rest of the world. Rather than anchoring to the skull, the sports headphones sit just in front of the ear, where your lower jaw meets your skull.
This is not entirely unlike how dolphins (and at least 65 species of toothed whales) detect sound.
Here’s the weird thing, though. Dolphins don’t have ears.
At least not externally. Dolphins are highly streamlined for fast travel through seawater and exposed, external ears would not only create drag but would produce cavitation and turbulence that could actually interfere with sound detection. Dolphins are, among other things, extreme audiophiles. So how do they hear? Nestled in their lower jaws is that same acoustic fat found in their big heads. Their lower jaws interface with the structures in their inner ear, allowing sound waves to travel up their jaw and into their ears. Dolphins “hear” with their jaws.
Thanks to the consumer drone movement, cheap time-of-flight LiDAR units (not true LiDAR systems that use laser reflection, but focused infrared emitters that do almost the same thing, but cheaper) are increasingly more available. These modules are compact, have a low power draw, interface easily with Arduino, and have a 12m operating range. Perfect! It’s not ultrasound, but it is a pretty good proxy for what I’m trying to build.
And if you want to try out bone conduction for yourself, Adafruit sells a bone conduction device for your own audio projects.