In the world of earphones, there are two ways unwanted ambient sounds are eliminated, either passively(isolation) or actively(cancellation).
Your UE fits custom earphones use passive noise isolation. Isolation is achieved by creating a perfect seal inside your ear canal with our custom molding tips. The snug seal and perfect fit you get after molding your custom tips will serve as a shield to block out unwanted noise while you listen to the crisp flow of your music, just the way it was intended to be.
On the other hand active noise cancellation is achieved by cancelling ambient sounds digitally.