Looks like a conventional rafter roof... Is there insulation between the ceiling and the roof??? If not, then that will help... Looks like you could get R-19 in there without much trouble... Of course, that means taking down the ceiling...

Plan B: Put siding over the gable and put in cross-ties/joists, insulate and drop the ceiling.... You can bring it down as far as you like... The more insulation, the less noise... Even bringing it down 12 inches would get you 12 inches more insulation/sound deadening... That will quite the heck out of it and you'll have a vaulted ceiling...

B~