Rock 'n' roll icon Ozzy Osbourne Friday announced he is retiring as the headliner of the annual heavy metal festival that bears his name. "After 10 years, the Ozzfest's name and reputation have been established," he said in a statement. "It's time for me to move on and do other things." He is expected to finish out this year's trek, but Osbourne's throat problems have forced Black Sabbath to step aside three times so far, MTV.com reported. The Osbourne camp has remained mum about the nature of the singer's voice problems and only posted notices on the tour's official Web site offering refunds to disappointed fans. Black Sabbath was in its headlining slot Thursday night in Tacoma, Wash., but a local newspaper review described a grimacing Osbourne trying to perform with a "hideously cracked" voice.