Sure, take drywall down or cut access holes for spray-in. There's some debate about whether it's acceptable to use spray-in where there's wiring, can be a pain later to service that, and in some situations can damage wiring. Also a light housing or fan, etc, may not be sealed so you have an expanding insulation mess.
Insulation may not be enough, depends on the noise sources and level of quiet you need. Many noise/sources resonate through the floors and walls anyway, can be felt, not just heard. This is especially true of impact forces upon anything attached to wall frames (doors and windows for example) or sitting on hard floors.