I'm a student in construction management. I would like to know, for the acoustical performance of exterior walls of residential building, how important is sound transmission class (STC) vs. noise reduction coefficient (NRC) . If you have to assign a weight to these two, how would you assign it (from 1-10)? I personally think, high STC rating is way more important than high NRC rating since residential building has small room space, so sound absorption won't be a big problem.

I agree. Residential is mostly about preventing noise transmission from outside and other rooms. 9.