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I can imagine some interesting potential applications, including weird ones.
I've been prototyping a dail-up concept (like CSD) over 2G networks. Combined with heavy server-side compressing, the goal is to achieve speeds faster than GPRS in areas that have no data coverage to speak of. TCP over sound was the first part. I'll have to study this implementation.
It should not be possible to exceed the carrier's CSD rate over the link, but it's an interesting way of circumventing their billing.
More interesting IMO would be to embed data stream into normal audio stream within human-audible range. Something like MP3 steganography, but decodable after air transfer. Had anyone tried that? I can imagine some interesting potential applications, including weird ones.
However it is technically trivial to encode "hidden" data at inaudible frequencies (>25 kHz) along with a song/whatever in the audible range and recover the data with a high pass filter. You would have to explain, however, the need for >48kHz sample rate.
Another, stealthier option would be to encode information in the background noise of a recording, but this would require more complex encoding/filtering techniques.
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Not sure if this is what you meant, but Chromecast's guest mode will pair using ultrasound. The guy who worked on it has some code using the WebAudio API on github and his linked blog: https://github.com/borismus/sonicnet.js
No there was an article on here several months ago that I couldn't find when searching where someone wrote a PoC for the transmission of data via near-ultrasonic sounds from a computer speaker and microphone. I don't think it was this [1] one, but it shows the concept being used. Maybe I'm misintepreting the OP's work and not realising how it differs in some subtle way? I get that they've put TCP/UDP over it, but is…
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>I don't mean sound converted to electricity, or to represent 0s and 1s, but using a specific frequency range to represent 1, another range to represent 2, another for 3... I don't know the terms for these things. Frequency-shift keying? https://en.wikipedia.org/wiki/Frequency-shift_keying
Yup, a company I co-founded http://chirp.io has been using this technique (well, MFSK) to share data over the air, between mobile and embedded devices for a while now. Easy to describe, hard to do robustly.
I have played with minimodem to do this (FSK) and while cool, it is an unpleasant noise. I managed to transmit at inaudible frequencies but certainly it was very very unreliable with normal consumer hardware.
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Good catch, but it was actually over audio signals. Sound was just for monitoring.
That's a distinction without a difference. If another family member picked up the phone while you were dialed up, they certainly heard it.
Clever, an audio soft-modem. Was there a reason to not implement this as an actual modem with a frequency band assigned to either channel and then to run SLIP or PPP over it?
Difficulty level, probably. I'd love to see both and also one that can survive over GSM audio (is that even possible?)
GPRS made that pretty much obsolete though.
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>I don't mean sound converted to electricity, or to represent 0s and 1s, but using a specific frequency range to represent 1, another range to represent 2, another for 3... I don't know the terms for these things. Frequency-shift keying? https://en.wikipedia.org/wiki/Frequency-shift_keying
Yup, a company I co-founded http://chirp.io has been using this technique (well, MFSK) to share data over the air, between mobile and embedded devices for a while now. Easy to describe, hard to do robustly.