Voice actors are increasingly on the front line of a transformation taking hold in the entertainment industry as the creativity of Hollywood and the technological innovation of Silicon Valley converge. Voice, that intimate marker of human emotion, is now seen as essential to the $24.5 billion U.S. video-game market, where the hyper-realistic graphics and operatic storylines used in games that can be as textured as the best film dramas. And the best voice actors - their names known to fans and promoted by companies - can become celebrities despite never appearing on-screen.