Mute or reduce sound of all headphones within certain range

Situation: Sitting (or standing) on the subway / bus / any public gathering - and the moron next to you is playing the lastest neo-funk-gospel-metal-nu-music on high volume. You only hear part of the music, the annoying part. To add to the torture is the lady on you other side also playing her waltz-hiphop-trombone-music on equally high volume. To avoid busting a vessel - your only option is to put on your own headphone and blast away with mazurka greatest hits. On high volume.

Or is it?

Imagine you have a little device in your pocket. One press on a button and all earpieces within 100 meters get their volume reduced to half.

Aaah. The peace and quite.