From what I have heard, the muzzle blast from an AK is usually a lot louder and more unpleasant then that from an AR15.  Is this true?

It depends on which end of the muzzle your hearing it from.  [;)]

if you standing next to me, while comparing my 16" AR w/ Kurts A2tac brake vs. Ak with 74 brake.. the guys at the range seem to dislike the AK the most, but thats due to the mechanics of the brakes being used.  As the shooter, I find my AR about 100% louder.  I also made the mistake hthis weekend of taking ONE shot without hearing protection.  Let's just say, I wont ever be doing that again!  I experienced immediate hearing loss accompanied by a slight vision impairment (due to very sensitive hearing).  Needles to say my senses went into shock mode.  My hearing in my left hear didnt fully restore until the next day.

If youve got an ak-74 type brake an ak will throw noise and crap all over anyone beside you. The armalite brake Im told is pretty nasty if yuor not the one firing it.