Your own electrical sea: sensing your movements

Your own electrical sea
by Paul Curzon, Queen Mary University of London

A silhouetted man holding up an umbrella as a lightning storm rages around him against a slate grey sky. He is holding a briefcase.
A man sheltering from an electrical storm Image by Gerd Altmann from Pixabay

You can’t see them, but there are waves of electricity flowing around you right now. Electricity leaks out of power lines, lights, computers and every other gadget nearby. Soon a computer may be able to track your movements by following the ripples you make in your own electromagnetic sea. Scientists at Microsoft Research in the US have figured out a way to sense the position of someone’s body by using it as an antenna.

Why would you want a computer to do this? So that you could control it just by moving your body. This is already possible with systems like the Xbox Kinect, but that works by tracking you with a camera, so you have to stay in front of it or it loses you. A system that uses your body as an electric antenna could follow you throughout a room, or even a whole building.

First you need an instrument that can sense the changes you make in your own electrical field as you move around. In the future, the researchers would like this to be a little gadget you could carry in your pocket, but the technology isn’t quite small enough yet. For this experiment, they used a wireless data sensor that’s about twice the size of a mobile phone. The volunteers wore it in a little backpack. All the electrical data it picked up were transmitted to a computer that would run the calculations to figure out how the user was moving.

Get moving

In their first experiment, the researchers wanted to find out whether their gadget could sense what movements their volunteers made. To do this, they had the volunteers take their sensing devices home and use them in two different rooms: the kitchen and the living room. Those two rooms are usually different from one another in interesting ways. Living rooms are usually big open spaces with only a few small appliances in them. Kitchens, though, are often small, and cram lots of big electricals in the same room. The electrical sensors would really have to work hard to make sense through the interference.

Once the experiment was ready to go, each volunteer ran through a series of twelve movements. Their exercises included waving, bending over, stepping to the right or left, and even a bit of kicking and punching. The sensor would collect the electrical readings and then send them to a laptop. What happened after that was a bit of artificial intelligence. The researchers used the first few rounds of movements to train the computer to recognise the electrical signatures of each movement. Later on, it was the computer’s job to match up the readings it got through the sensor to the gestures it already knew. That’s a technique called machine learning.

One of the surprising things that made the sensor’s job tougher was that electrical appliances change what they are doing more often than you think. Maybe a refrigerator switches its cooling on and off, or a computer starts up its hard disk. Each of these changes means a change in the electrical waves flowing through the room, and the computer had to recognise each gesture through the changing noise.

Where’d you go?

The next step for the system was to see if it could recognise which room someone was standing in when they performed the movements. There were now eight locations to keep straight – two locations in one large room and six more scattered throughout the house. It was up to the system to learn the electrical signature for each room, as well as the signature for each movement. That’s pretty tough work. But it worked well – really well. The system was able to guess the room almost 100% of the time. What’s more, they found that the location tracking even worked on the data from the first experiment, when they were only supposed to be looking at movements. But the electrical signatures of each room were built into that data too, and the system was expert enough to pick them out.

Putting it all together

In the future the researchers are hoping that their gadgets will become small enough to carry around with you wherever you are in a building. This could allow you to control computers within your house, or switch things on and off just by making certain movements. The fact that the system can sense your location might mean that you could use the same gestures to do different things. Maybe in the living room a punch would turn on the television, but in the kitchen it would start the microwave. Whatever the case, it’s a great way to use the invisible flow of energy all around us.


This article was originally published on CS4FN and can also be found on pages 14-15 of CS4FN Issue 15, Does your computer understand you?, which you can download as a PDF. All of our free material can be downloaded here:


Machines Inventing Musical Instruments

by Paul Curzon, Queen Mary University of London

based on a 2016 talk by Rebecca Fiebrink

cupped hands in dark
Image by Milada Vigerova from Pixabay
Image by Milada Vigerova from Pixabay 

Machine Learning is the technology driving driverless cars, recognising faces in your photo collection and more, but how could it help machines invent new instruments? Rebecca Fiebrink of Goldsmiths, University of London is finding out.

Rebecca is helping composers and instrument builders to design new musical instruments and giving them new ways to perform. Her work has also shown that machine learning provides an alternative to programming as a way to quickly turn design ideas into prototypes that can be tested.

Suppose you want to create a new drum machine-based musical instrument that is controlled by the wave of a hand: perhaps a fist means one beat, whereas waggling your fingers brings in a different beat. To program a prototype of your idea, you would need to write code that could recognize all the different hand gestures, perhaps based on a video feed. You would then have some kind of decision code that chose the appropriate beat. The second part is not too hard, perhaps, but writing code to recognize specific gestures in video is a lot harder, needing sophisticated programming skills. Rebecca wants even young children to be able to do it!

How can machine learning help? Rebecca has developed a machine learning program with a difference. It takes sensor input – sound, video, in fact just about any kind of sensor you can imagine. It then watches, listens…senses what is happening and learns to associate what it senses with different actions it should take. With the drum machine example, you would first select one of the kinds of beats. You then make the gesture that should trigger it: a fist perhaps. You do that a few times so it can learn what a fist looks like. It learns that the patterns it is sensing are to be linked with the beat you selected. Then you select the next beat and show it the next gesture – waggling your fingers – until it has seen enough examples. You keep doing this with each different gesture you want to control the instrument. In just a few minutes you have a working machine to try. It is learning by example how the instrument you are wanting works. You can try it, and then adjust it by showing it new examples if it doesn’t quite do what you want.

It is learning by example how
the instrument you are wanting works.

Rebecca realised that this approach of learning by example gives a really powerful new way to support creativity: to help designers design. In the traditional ways machine learning is used, you start with lots of examples of the things that you want it to recognize – lots of pictures of cats and dogs, perhaps. You know the difference, so label all these training pictures as cats or dogs, so it knows which to form the two patterns from. Your aim is for the machine to learn the difference between cat and dog patterns so it can decide for itself when it sees new pictures.

When designing something like a new musical instrument though, you don’t actually know exactly what you want at the start. You have a general idea but will work out the specifics as you go. You tinker with the design, trying new things and keeping the ideas that work, gradually refining your thoughts about what you want as you refine the design of the instrument. The machine learning program can even help by making mistakes – it might not have learnt exactly what you were thinking but as a result makes some really exciting sound you never thought of. You can then explore that new idea.

One of Rebecca’s motivations in wanting to design new instruments is to create accessible instruments that people with a wide range of illness and disability can play. The idea is to adapt the instrument to the kinds of movement the person can actually do. The result is a tailored instrument perfect for each person. An advantage of this approach is you can turn a whole room, say, into an instrument so that every movement does something: an instrument that it’s impossible not to play. It is a play space to explore.

Playing an instrument suddenly really is just playing.

More on …