Desmond Is Deaf

Taken from an article, here is what was said:

Ian Somerhalder - aka season one casualty Boone - is back! He'll be appearing, not via flashback, in Locke's visions in an early episode of season three - sending him on a hunt to uncover another of the island's hidden secrets. Meanwhile, Desmond and Eko also survive the hatch explosion - but the former loses his hearing in the process.

Digital Spy