[roman_zeyde]

~3 meters is indeed quite a challenging scenario. I've tested it with the lowest bit-rate supported (1 kbps), but it doesn't work reliably.

You can try my Android app [1] to reproduce the experiments for short transmissions.

[1] https://play.google.com/store/apps/details?id=bit.zeyde.audi...

[ChuckMcM]

Nicely done, I'll note for the readership here that a similar technique works fine at 300 baud across the room using FSK.

Something you might consider is to write a web camera backend for it and use the screen/webcam. That has a lot more bandwidth and has higher SNR as the selector effect of the web camera is so much better than that of a microphone.

[brian-armstrong]

FSK across the room? Does that have noise restrictions?

I’ve found all the phase modulation schemes work poorly across the room. DSSS works ok but is very slow. I would be curious how reliable FSK is in that situation.

[noir_lord]

hmm, if you where using a screen/webcam, could you do something horribly crude like flash QR codes and leverage their EC?.