I wonder, if instead of "noise cancelling", you could use "noise incorporating" head phones. Listen to the environment, and pick the songs from the users library, that most closely match the BPM of that washing machine, or the drone of the engine for the bus you're in. Maybe slightly tweak it's speed to fully sync it up?

I like noise cancelling, but I can imagine noise incorporating could be a more _fun_ solution. Letting you live with the noise, instead of removing it.

For a more chaotic noise, like a construction site, this would be really hard. But maybe with some machine learning still possible?