Ultimate iPod for Loud Places

Sound waves can be minimized or amplified by adding waves of different wave lengths.  An example of destructive sound wave technology is in some luxury vehicles there is a microphone that records noise entering in the cab of the vehicle.  An on board computer processes the sound waves coming into the car and then tells the speakers to emit a sound in equal but opposite wavelength.  The two waves cancel each other out and the cab is quiet.  Take that same technology and apply it to the ipod.  You want to ride the subway and listen to your music without drawing blood from your ear drums.  Or you could mow the lawn and keep your volume at a minimum the ipod would offset the noise of the mower.