Earphone Echolocation

Most people don’t like bats. There are probably ingrained and insidious reasons as long as time itself for this. There is Dracula I suppose and it is October, spookiness abounds and you never know with all the ghosts and ghouls roaming about. Most people don’t like bats, but everyone knows they’re “blind” yet manage to fly using sonar.

I had the opportunity ages ago to do some research with a blind charity in London which helped blind people get jobs. One of the things you need to know is that (at least in the UK), only about 4% of people categorised as blind are in fact totally blind. Most have some type of sight impairment that means they are legally blind but might be able to just see for instance only peripherally or maybe motion in tones without any sort of definition. It was damn inspiring and speaking with these people still sticks with me over a decade later. One guy trained as a paralegal and because he could listen to text to speech at 8x (take that west coast consumption optimisers) he could go through a legal deposition so much faster than someone without sight issues. You can do a lot with sound it seems.

So back to bats. We all know about echolocation, right? The thing that bats do. They emit a sound, it bounces off objects back at them and then they can “hear” where things are. Sonar. Fun fact: Humans can do it as well. Daniel Kish, who is blind, in this video shows how he uses clicks so he doesn’t hit a parked car and other things. Whilst on a bike mind you. Just like a bat. Human sonar. In fact, at the University of Alcalá in Madrid, Spain, they managed to teach ten non-blind participants basic sonar navigation skills over a number of days. That is amazing. Just like Morse Code, we can learn other non-visual ways to we navigate through the fabric of life.

If you walk down the street, there is a non-trivial chance you or 20% of the people you see are wearing headphones. They are everywhere and they are a sonic communication device right on our heads.

Bats use ultrasonic frequencies (above human hearing range of ~20 kHz) for their sonar. Headphones or earbuds could also emit ultrasonic frequencies (above 20 kHz) that most adults can’t hear. These would bounce off objects and return signal about things in space. The microphones in the headphones could capture the reflected signals analyse time delay (distance to objects), amplitude changes (object size/material) and frequency shifts (Doppler effect for moving objects). Sonar with headphones. “Seeing” with sound.

The headphones could translate this to sound cues (sound going up or down if you’re closer or farther from it), haptic feedback or even spatial audio that you could sort of feel the space. So it’s quite possible you could hear and then understand space and what is in it with your headphones without seeing a thing with your eyes.

Ultrasonic signals don’t travel as far as the audible clicks like our guy Daniel Kish, and most bats are detecting insects and obstacles at only 1–5 metres. So ultrasound doesn’t go that far. But you would hear the clicks and so would the people around you. So socially awkward and potentially annoying.

So what do you do with all of this? What about being able to see things that are not in front of you? Seeing behind you but with sound. This of course would have industrial and probably some sort of military applications. It would of course potentially be useful for the blind or working in low-light situations. Maybe even for people on phones just walking so they don’t bump into things or get run over by cars?

But what about this idea of hearing the spatial sense of the world around us? We all now can’t live without digital maps, but why do maps have to be visual when the way our brains can understand space without it? Like with landmarks.

What if there were acoustic markers, things in space with distinctive echo signatures, things with specific shapes, materials or textures designed to produce recognisable sonic reflections. Certain objects or places, let’s say a statue, a door, pillar, a room “sounded” differently when you were near them, building up a sound based, mental-spatial map.

Anyhow, you can do loads with headphone based sonar, just think of it. And don’t think of how much you hate bats.