According to his Wikipedia entry, Black Bolt “triggers a massive disturbance in the form of a highly destructive shockwave capable of leveling a city” merely by speaking. On the bright side, that means he’ll probably be quiet if you take him to a movie theater.
Black Bolt is also the newest hero in Gazillion’s Marvel Heroes Omega, recently added to PlayStation 4 and Xbox One alongside his appearance in the premiere of Marvel’s Inhumans on ABC. As befits his character, he’s mostly silent, though capable of releasing the destructive power of his voice when the need arises. As the press release announcing his arrival puts it: “His actions don’t speak louder than his words—his words are his actions.”
In the game, Black Bolt has a mix of melee and energy powers, while his ultimate ability, Royal Decree — his is king of the Inhumans, after all — “unleashes the full potential of his voice in a reality-rending yell that instantly vaporizes non-boss enemies and decimates everything else.” Remind me not to invite him to karaoke night.