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Transmitting data via ultrasound without any special equipment

Transmitting data via ultrasound without any special equipment

3 comments

·June 27, 2025
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thijson

It might be useful to study the techniques that modems used to transmit data over phone lines. I seem to recall trellis coded modulation being used:

https://en.wikipedia.org/wiki/Trellis_coded_modulation

The acoustic channel is bound to suffer from multipath too, so some equalization may be needed too.

https://en.wikipedia.org/wiki/Equalization_(communications) https://www.ti.com/lit/an/spra140/spra140.pdf

In order to receive the signal far from the transmitter, some form of spread spectrum encoding could be used, like CDMA. The spreading factor could be negotiated.

https://en.wikipedia.org/wiki/Direct-sequence_spread_spectru...

adzm

The web tool is fun! I decided to give it a harder test and turned up some fans and background music up pretty loud and it still managed to decode the message.

Though after a certain point it stops recognizing it, I was still surprised how well it did with noise. I'm sure noise in higher frequencies (or the right harmonics) would be much harder to handle, but solvable in interesting ways too

ac29

See also: https://github.com/ggerganov/ggwave