LOL
I'm sure stupid iSheep will be queuing up to buy this snake oil.
Poor iPod performance getting you down? Then boost its audio accuracy with Sound Jacket which, manufacturer Radiopaq claims, significantly improves the sound quality of MP3 music tracks. Radiopaq_soundjacket_01 Radiopaq's Sound Jacket: improves MP3 audio Compatible with the fourth-generation iPod Nano, Radio Jacket …
It's a compressed file. Unless it's going to the internet and looking up an uncompressed version of the file, the detail isn't hidden. It ain't there.
So, if the statement is even vaguely true (and not just marketing bollocks) what it is actually doing is having a stab in the dark and making up extra detail as it goes along. Although that probably doesn't sound quite so impressive in the marketing blurb.