the 1 1/2 t&g is not too bad for sound, in my experience.
my sister built a house with a timberframe second floor deck which was hung in conventional stick framing. They then laid 1 1/2 decking and nothing else for the second floor.
They have 3 kids, and those devils can be playing fairly rough upstairs before we hear them. Footsteps above are very faint sounding,and the impact of chairs being thrown or bodies falling from the top bunk bed comes through as a dull sound, not too sharp.
I built a house for my family and used a system with 1/2" drywall, then 2x2" strapping(16" centers) with fiberglass insulation(tear 2x4 in half), then 3/4" t&g hardwood which worked as well or better than the 1 1/2".
