In range or training setting hearing protection is always worn but in combat it can't be. So my question is assuming an infantryman is armed with an M16 or M4 (5.56) can he expect to suffer permanent hearing damage after a firefight? How about in an urban or indoor CQB scenario?  

The answer is YES and YES. My company manufactures weapon systems for LE and we now strongly suggest that all CQB weapons have suppressors on them. This will not only help to save the hearing of the officers but it helps to keep them hearing commands and info over their radios. Hearing loss for these officers can be reduced significantly by the use of suppressed weapons. This also stops the noise from the blast being heard outside the room, this can be very important in an inner city gun fight or raid. By this I mean response from onlookers who may be offended by the use of deadly force.

WHAT!!!!???