building a studio in Delhi, India, couple of questions

[spaceman]

I am planning on building a studio on the first floor of my house, in Delhi, India, where houses are build with a flat concrete roof so that another floor can be added later.
The outer walls and supporting walls are 11 inches thick, a brick core lined with concrete on both sides, the room walls are brick and concrete but only 5 inches thick, the upstairs wall that are not supported, such as between the control room and the live room, will have to be the thin 5 inches kind.
My question is; are those thinner walls soundproof ? Should I plan 2 walls with an air gap between them?
I am planning on installing fixed windows on aluminum frames, installing 2 sets of window, using the thickness of the wall as the air gap. would that work at keeping the traffic noise and permanent honking in and drums sound in?