Wifi Theremin
aaron posted in most unnecessary, wifi on January 19th, 2009
A theremin, for those who don’t already know, is a musical instrument that varies the pitch based on your proximity to an antenna, and varies the volume based on your proximity to another antenna. It’s a touch-less device, and you’d probably recognize the sound from old sci-fi movies (listen to the vibrato whistling sound in the background).
Here’s an example of a theremin:
So what does this have to do with anything? I wrote up a script that has the same functionality that uses a wifi device and its signal strength to control the frequency and volume. Yeah, pretty useless, but yet here it is. We actually did this a couple years ago at MRL, but that version was even more of a hack. This version will actually interpolate the pitch as the signal strength jumps around and is threaded so the sound is a little smoother. This version also allows for a second control (wifi interface) that corresponds with the volume so it is a little bit more like a real theremin. There’s still a decent amount of latency though, so you can’t really use it to create useful music.
Here’s a short sample of what it sounds like when you run it from my system. Now isn’t that a beautiful sound, 
.
I started creating this on my mac book pro, but after realizing the embedded antenna is pretty difficult to control the signal strength from, I added support for linux. It’s not doing anything fancy for reading signal strength (just parsing CLI utils), so I’m not sure how portable it really is. Also, it does have a couple dependencies on audio libraries, but they’re pretty easy to install (in case you really care).
Anyway, Have fun!
January 23rd, 2009 at 5:34 pm
[...] Labs have put together a new toy for you to play with. It’s a Python script that makes your WiFi hardware behave more like a theremin. Based on the pyaudio library it monitors the signal strength of the AP you’re connected to [...]
January 24th, 2009 at 8:06 am
On my System the script died cause of slightly different iwconfig output. I hope this Patch is a bit more portable:
Change line
153: cmd = “iwconfig %s | grep ‘Signal level’ | cut -f2 -d: | cut -f1 -d’ ‘” % device ]
to
cmd = “iwconfig %s | grep ‘ignal level’”
and Line
161: signal = signal.rstrip()
to
x=signal.index(“ignal level=”)+len(“ignal level=”)
signal = signal[x:signal.index(" ",x)]
January 24th, 2009 at 11:55 am
[...] Labs have put together a new toy for you to play with. It’s a Python script that makes your WiFi hardware behave more like a theremin. Based on the pyaudio library it monitors the signal strength of the AP you’re connected to [...]
January 24th, 2009 at 9:05 pm
[...] Labs have put together a new toy for you to play with. It’s a Python script that makes your WiFi hardware behave more like a theremin. Based on the pyaudio library it monitors the signal strength of the AP you’re connected to [...]
January 26th, 2009 at 11:11 am
[...] Midnight Research Labs describes a nifty theremin hack implemented by detecting signal strength of a WIFI signal. Python source is available to examine. [...]
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