Sounds (no pun intended) like a solution to a problem that, really, has already been solved. Existing noise-cancelling earbuds, like those sold by Shure, significantly cut down on outside noise levels enough to allow users to lower the volume on their music, and still hear all those nuances.
As to whether heavy metal actually has "nuances"...
__________________ Steven Lyle Jordan: Original SF so good, Fox would never put in on the air.