Some folks like to cancel noise but using a microphone on a headphone not only is less than 70% efficient, it cancels a lot of stuff you sometimes need to hear.
It would be much better if _ you_ were creating the noise.
The waveform, speaker and headphones would all be designed together and optimized so that 99% of the "noise" could be cancelled.
No one else could hear anything but you could hear a pin drop.
The wage form needs to be a compromise between a square wave and the easiest to cancel waveform.
The system would determine the beat and major frequencies of the music next door or the next lane and join in with a one or two measure delay or echo except 20 decibels louder and at 5% lower slowly fluctuating major frequencies.
The speaker would necessarily present a large target and therefore should be designed out of sheet steel so that it can be cheaply and quickly replaced when it acquires too many holes.
This could be a real money maker for Bose or who ever designs and patents it first.
Bret Cahill