[OANNES Foro] Homemade glasses let you see like a dolphin

[Mario Cabrejos]

I built a head-mounted LiDAR array that lets you see the world like a
dolphin via vibrations sent through your jaw.

by  <http://www.southernfriedscience.com/author/southern-fried-scientist/>
Andrew David Thaler

July 24, 2018

http://www.southernfriedscience.com/i-built-a-head-mounted-lidar-array-that-
lets-you-see-the-world-like-a-dolphin-via-vibrations-sent-through-your-jaw/

 

I'm Andrew Thaler and I
<http://www.southernfriedscience.com/how-to-build-a-canoe-from-scratch-on-a-
graduate-student-stipend/> build
<http://www.southernfriedscience.com/meet-sea-leveler-the-open-source-water-
level-gauge-that-want-you-to-talk-about-sealevelrise/> weird
<http://www.southernfriedscience.com/how-to-drownyourtown-a-step-by-step-gui
de-to-modelling-sea-level-rise-in-google-earth/> 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?

The author wearing a head mounted LiDAR array, looking very pensive. 

Spoilers: You can. Photo by A. Freitag.

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. 

Dolphins, like bats, have a biosonar system that allows them to detect
objects through echolocation. That big, bulbous head of theirs is filled
with acoustic fat, a dense lipid that allows them to focus sound. Those
sounds are created by a vocal structure under their blowhole called the
dorsal bursae-monkey lips complex and honestly I'm only going into so much
detail here because of how great that name is. Ultrasonic clicks travel from
the monkey lips complex through the acoustic fat-filled melon, and emanates
out the front of the melon. Those clicks then bounce off objects in the
ocean and return to the dolphin, who somehow translates that information
into spatial awareness.

A cross-section of a dolphin head, showing sound production and travel
through the melon. 

A slice of dolphin, showing how sound is produced. From Au and Simmons 2007.

Incidentally, we only
<https://www.journals.uchicago.edu/doi/pdfplus/10.2307/1539374> confirmed
that dolphins can echolocate in the 1960's, which feels really late to me
considering that barely 30 years later we were already
<https://en.wikipedia.org/wiki/Ecco_the_Dolphin> making video game for kids
as if it were universal common knowledge.

 

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.

For a really good overview of dolphin (and bat) biosonar, check out
<https://physicstoday.scitation.org/doi/10.1063/1.2784683> Au and Simmons
(2007) Echolocation in Dolphins and Bats. DOI: 10.1063/1.2784683. It's not
open access, but there's probably some sort of Hub for Science where you
could easily find a copy.

So, consumer bone-conducting headphones that sit at the interface of your
jaw and skull is a pretty good proxy for how dolphins receive sound, but how
do we produce it?

The ubiquitous  <https://amzn.to/2NHrB6e> ultrasonic rangefinder that seems
to come packaged in every Arduino kit was the first obvious answer. Dolphins
use ultrasound, so why shouldn't we start there? After a bit of tinkering, I
realized that the device has a major limitation: it's range is tiny; barely
a meter on a good day with perfect conditions. Long range units get
exponentially more expensive and consume increasingly large amounts of
power. I wanted a head-mounted dolphin-inspired echolocation system that was
compact!

 

Thanks to the consumer drone movement, <https://amzn.to/2mE9pPy>  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.

 

A LiDAR unit mounted to a pair of lasercut glasses with the control box in
the background. 

DolphinView.

Finally, I harnessed the power of the  <https://amzn.to/2uLwcNM> Glowforge
to cut the housing and head-mount from some black acrylic, combined a slew
of extra components for charging and driving the audio signal to a pair of
headphones, bashed out a quick and dirty bit of code to get everything
talking, strapped a LiDAR unit to a pair of lasercut glasses with a mounting
bracket, and DolphinView was born!

Don't worry, it's all open-source and ready to build. The shapefiles, bill
of materials, code, and associated documentation is all on GitHub as well as
Thingiverse.

*	GitHub:  <https://github.com/SouthernFriedScientist/DolphinView>
DolphinView - A LiDAR system to convert distance measurements into signal
pulses in bone-conducting headphones.
*	Thinigiverse:  <https://www.thingiverse.com/thing:3017746>
Head-mounted LiDAR array that communicates through bone conduction.

 

Taking the system on a test drive through our local park was a weird
experience. Having full hearing plus a constant drum beat of clicks alerting
me to the closeness of whatever object was directly ahead of me was a bit
surreal and it took a while to get used to the sensory overload. 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 could function independently. Because of how the delay function work,
it doesn't do a great job telling you if something is heading straight
towards you at high speeds. It would be interesting to add an ultrasonic
rangefinder to let the wearer sense things closer than the LiDAR's 30cm
minimum distance.

Walking around, you definitely do start building up a sense of what all the
clicks mean, and with a little practice, you can easily pick out thinks like
open doorways with your eyes closed*.

We don't actually know what dolphins "see" when they project sounds at
complex objects. From experiments and models, we know that they can perceive
thickness as well as distance from target objects. Without being inside a
dolphins brain we have no real way of knowing if they can form complex,
3-dimensional models of the world through biosonar alone or if it acts more
like the sweeping pings of a ship's SONAR.

These kinds of projects are not nearly as daunting as you might think. From
conception to realization was less than 2 days (excluding shipping time).
The code is barely 15 lines, most of which if cobbled from existing code.
The lasercut pieces are nice, but not necessary. The entire build cost less
than $100. Documentation took almost as long as actually building the thing.

So get out there and make weird things!

  _____  

If you're not sure where to start,  <https://amzn.to/2NGdJsX> 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
sensor systems.

 



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