Meanwhile at the other end of the spectrum
Internet Protocol over Xylophone Players (IPoXP)
http://www.youtube.com/watch?v=qCT7SisWh38
Japanese boffins at Tokyo’s Keio university have been showing off new transmission technology which uses ultrasonic waves to send digital information in highly directional bursts. Unveiled at the Open Research Forum 2012 in the capital last week, SteganoSonic features two plates covered in small ultrasonic speakers and a …
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for directional sound transmission ... sounds like a neat idea, but surely has been done before? So now they coupled that technology to the good old modem?
Just for reference, the register already carries stories about phase manipulation for radio waves for magical information multiplexing (twisted radio) or to build better antennas (super antenna) and elsewhere scientists play with photon phases to achieve the same goal ('photons with helical phase structure'). Seems to be all the rage for information transfer those days.
It's worse than we thought. Directional ultrasonic acoustic devices have been in existence 10+ years, operating in the utlrasonic 200kHz-220kHz range to carry audio which is demodulated using sum and difference tones within a small space confined by the acoustic collimation. For example, combining 201.000kHz and 200.000kHz creates an intermodulation tone of f1-f2 which is 1.000kHz. The perceived effect is uncanny - you take a step into the 'hot' spot and suddenly you u hear music. Practical devices havs been investigated by the Coca-cola company to create an 'ambience' around vending machines, and by the US DoD in higher power versions to create a different kind of 'ambience'.