Quietnet: a simple chat program using inaudible sounds
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The future is now. An anonymous Pipedotter wrote it to direct out attention to quietnet, a program that does just that. It is a simple chat program that works without Wifi or Bluetooth connections and won't show up in a pcap. You need a good pair of speakers to make it work: If you can clearly hear the send script working then your speakers may not be high quality enough to produce sounds in the near ultrasonic range.
Quietnet is dependant on pyaudio[1] and Numpy[2].
[1] http://people.csail.mit.edu/hubert/pyaudio/
[2] http://www.numpy.org/
The same Anonymous Coward notes: "Quietnet is just a toy! Take a look at minimodem[3] or gnuradio[4] if you need something robust."
[3] http://www.whence.com/minimodem/
[4] http://gnuradio.org/
[Ed. note: looks pretty interesting. Time to test out my cat's audio frequency sensitivity, that fuzzy bastard.]