Well, yes and no. You have to frame a cube or rectangle, then apply clips and channels to all these surfaces, insulate and then apply double drywall. Pretty tight quarters become even tighter.
Also hard to get competent ventilation in there without compromizing what was just built.
Can and is certainly done, but it's not as straightforward as the walls, and you wind up with a surprisingly smaller space, making it maybe less than worthwhile.
The Soundproofing Company