There was some speculation in the Underworld series that his speaking voice was deepened artificially, but his natural speaking voice is really that deep.
[regarding his Underworld character Raze] Because the way modern
movie-making sensibilities are concerned, if you don't have a name,
then who are you? We didn't want to make the part too big, because if
we did, they'd get a rapper like LL Cool J. He's good, and so is Ice
Cube, but I wanted to play this, so we had to knock it down so it would
be unattractive to any rapper.