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I would suspect those environments to be much too noisy for that to work.

Unless it's noisy at or near the desired communication frequency, it is trivial to isolate the signal and completely mute out the noise.

In this example, at ~19 kHz, a properly configured high-pass filter could easily remove any human-talking sounds.

I'm not worried about humans talking, I'm worried about the ambient noise of the train/plane itself.

Agreed. This particular app starts to fail badly when the AC is on my current room. Airplanes are much, much, worse.