From Prefix via The Big Picture, it's a recording of "Smells Like Teen Spirit" like you've never heard it before. This version, which someone posted to Youtube, isolates Kurt Cobain's voice, so his vocals cut through long and prolific silences instead of instrumentation. Contrary to what your parents might have thought, Cobain did have quite a voice (it's not just noise dad!), and this excised version gets that across even more vividly than his acoustic sessions. If you listen below, be patient during the first stretch of silence -- it does end, and it's worth the build-up. For comparison's sake, we've also posted the song sans manipulation below.
LISTEN to Cobain's vocals on "Smells Like Teen Spirit":
WATCH the official video for "Smells Like Teen Spirit":