I dont know, i just thought it was his way of portraying a tightly leashed energy, sort of just seething under the skin, waiting to burst out. believe me, i have seen him do the loud variety also...he is very good at it. actually awesome at it too...but here the character isnt just angry or violent, he is the brooding, dark , seething kind of guy ...like a volcano that quietly boils but erupts only once in a while...he doesnt show his anger, hardly ever raises his voice, uses great economy of words and speaks mostly through his eyes...but then, boy , does he speak!!! Its a very difficult charaxter to etch out, we have so much difficulty in describing his facets, imagine how hard it is for an actor to portray all its layers and unravel them one by one.
he is doing a gud job ,quite netural ... over loud fake lagta hai , i saw many heroes who does det type of acting but in d end it luked fake , dramatic , her scene mai shout karna is not necessary to show det u r a angry rude man