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I am Andrew Thaler and I Construct Strange Things
Last month, while traveling to Kuching for Make for the Planet Borneo, I had an idea for the next strange ocean education project: and if we could use bone conductive headphones to "see" the world as a dolphin through the echolocation?
Spoilers: You can. Photo by A. Freitag.
Bone conduction headphones use speakers or tiny motors to send vibrations directly into the bones of your skull. It works surprisingly well for listening to music or amplifying voices without clogging the ear. The first time you try it, it's a strange experience. Although you hear the sound well, you do not feel like it's going through your ears. Bone conduction has long been used in hearing aids as well as in military and industrial-grade communication systems, but the technology has recently emerged in sports headphones for people who want to listen to music and podcasts without disconnecting the rest of the world. Rather than anchoring to the skull, the sport headphones are right in front of the ear, where the lower jaw joins the skull.
This is not completely different from the way dolphins (and at least 65 species of toothed whales) detect sound.
Dolphins, like bats, have a biosonary system that allows them to detect objects by echolocation. This large bulbous head is filled with acoustic fat, a dense lipid that allows them to concentrate the sound. These sounds are created by a vocal structure beneath their blowhole called the dorsal complex bursae-monkey lips and honestly, I only go into so much detail here because of how big name is. Ultrasonic clicks move from the complex of monkey lips through the fat-filled melon fat, and emanate from the front of the melon. These clicks then bounce off objects in the ocean and return to the dolphin, which in one way or another translates this information into spatial awareness.
A slice of dolphin, showing how the sound is produced. Incidentally, we have only confirmed that dolphins can echo in the 1960s, which seems to me really late since barely 30 years later we were already doing a video game for kids as if it was a universal common knowledge.
Here is the strange thing, though. Dolphins do not have ears.
At least not on the outside. The dolphins are very streamlined for a quick voyage through seawater and exposed, the outer ears not only create a trail but produce cavitation and turbulence that could actually interfere with sound detection. Dolphins are, among others, extreme audiophiles. So, how do they hear? Nestled in their lower jaws is this same acoustic fat found in their big heads. Their lower jaws interface with the structures of their inner ear, allowing sound waves to move their jaws up to their ears. The dolphins "hear" with their jaws.
For a very good overview of the biosonar of dolphins (and bats), see Au and Simmons (2007) Echolocation in dolphins and bats. DOI: 10.1063 / 1.2784683 . This is not open access, but there is probably some kind of Hub for Science where you can easily find a copy.
Thus, the bone conductive headphones that are at the interface of your jaw and your skull are a good proxy for dolphins to receive sound, but how to produce it?
The omnipresent ultrasonic rangefinder that seems to come packaged in every Arduino kit was the first obvious answer. Dolphins use ultrasound, so why not start there? After a little DIY, I realized that the camera had a major limitation: its reach is tiny; barely a meter on a good day with perfect conditions. Long range units become exponentially more expensive and consume more and more energy. I wanted an echolocation system inspired by dolphins that is compact!
Thanks to the movement of mass-market drones, time-of-flight LiDAR units (no real LiDAR systems that use laser reflection, but focused infrared emitters that do almost the same, but cheaper) are becoming more available. These modules are compact, have low power consumption, easily interface with Arduino and have an operating range of 12m. Perfect! It's not an ultrasound, but it's a very good proxy for what I'm trying to build.
DolphinView
Finally, I leveraged the power of the Glowforge to cut the case and the mounting head of black acrylic, combined a series of additional components for load and drive the audio signal to a pair of headphones, ripped a piece of code fast and dirty to make everything talk, attached a LiDAR unit to a pair of lasercut glasses with a mounting bracket, and DolphinView was born!
Do not worry, everything is open-source and ready to build. Shapefiles, BOM, code, and related documentation are all on GitHub and Thingiverse.
Taking a test drive in our local park was a strange experience. Having a complete audition and a constant beating of clicks alerting me of the proximity of the object that was directly in front of me was a bit surreal and it took a while to get used to the overload sensory. The system is far from perfect and would benefit from the extra processing power you could get from something like a Raspberry Pi so that the audio driver and LiDAR can run independently. Because of the timing function, it does not tell you very well if something goes straight to you at high speed. It would be interesting to add an ultrasonic rangefinder to allow the wearer to feel things closer than the minimum distance of 30 cm from the LiDAR.
As you walk, you begin to understand what all clicks mean, and with a little practice you can easily spot thinks like open doors with your eyes closed *.
We do not really know what dolphins "see" when they project sounds on complex objects. From experiments and models, we know that they can perceive the thickness as well as the distance of the target objects. Without being inside a dolphin brain, we have no way of knowing if they can form complex and three-dimensional models of the world through biosonar alone or s & d. It acts more like the fast pings of a ship's SONAR
are not as intimidating as you might think. From conception to completion, less than 2 days (excluding delivery time). The code is barely 15 lines, mostly if tinkered with existing code. The lasercut pieces are nice, but not necessary. The entire building costs less than $ 100. The documentation took almost as long as the construction of the thing.
So get out and do weird things!
If You Do not Know Where to Start, Environmental Monitoring with Arduino: Building Simple Devices to Collect Data About the World around Us is a fantastic book to introduce you to the world of DIY probe.
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* Look, I know what you think. Yes, perhaps, perhaps a much more refined iteration of this could be a helpful aid for people with visual impairments. But it's a clumsy thing that I've played together in a few days to teach kids about dolphins. Throwing random pieces of technology into the ether is much less appealing than simply making society and public spaces hospitable and accessible to people of all abilities.
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