Insulation in an interior wall

Hi, I am finishing a bonus room (turning attic space into a home theater) and am considering what to do with the existing insulation. The unfinished space is next to an existing bedroom. The between the bedroom and the home theater to be is currently insulated with R-15 batts. I Know it doesn't do much but I am considering leaving the batts in to help with sound dampening.

Two questions I could use your advice on:

1) Is this going to do anything to help with sound dampening or am I just wasting time by not ripping the existing stuff out entirely?

2) The insulation is kraft faced R-15. If I decide to leave it in the wall (which will be between two heated spaces) do I need to pull out the insulation, rip off the paper facing and then stuff it back in?

Thanks!