What would happen if Black Bolt...

...sneezed?

He can't control whether he sneezes or not, and a sneeze would wipe out half the planet. So what does he do about it?

his attack is based on vocals not on breath. If he sneezed it would just have to be an outwards blow and not an actual "AAACHOOO"...

But a whisper is breath, not vocals, and he uses that as an attack.

good point... I don't know.. all I know is that his attack is tied to his vocal cords. Odd when you mention it.

Yes. Nobody can meditate to stop themselves from sneezing.

actually he can, he hasnt ever sneezed.. i geuss you just need discipline really, because you can stop yourself from sneezing (Without holding ur nose lol)

Whispers, when he uses them, are vocal. Basically, if he engages the speech center of his brain, the shockwave is produced, at varying levels. So he could sneeze, maybe whistle, etc.