At least by the accounts of those watching the show. If you happened to have caught the show on television, then, er, you probably noticed that Adele didn't quite sound like Adele. According to Adele, her mics were a bit off but nobody in the audience actually noticed -- because the mix ups weren't of the kind that affected her live performance.
Express claims that Justin Bieber is behind the mess up of Adele's microphones that were used to broadcast her voice on television, some of which, reps for Justin Bieber allegedly denied in later reports.
Fans speculated online of the noises that were heard (and, our own critics at home heard them during the broadcast). Most picked up on the fact that they sounded like an acoustic guitar, some of which, Bieber later walked on stage with.