Actually this discussion has been extremely helpful. Ultimately I imagine it’s going to be on us to select the soundproofing strategy (of course based on input from an expert) that we are most comfortable will work, and there have been lots of great ideas mentioned here in this discussion.
This detail does not comply with code. They missed 722.6.1.1, max 60 min for calculated wood/gyp assemblies. Gyp does not necessarily need to be continuous, but a rated assembly does. You can change assemblies as you go up the wall if they all meet the requirements.
Absolutely. And a lot of acoustical consultants would say that the continous ply had to be gapped. I don't know if that can be saw cut and maintain the structural integrity of the joists.
you said: "The continuous plywood floor sheathing seems very questionable"
You may be right, probably are, but it's short circuiting the acoustic separation and, as a non-expert in fire rated partitions, the fire resistance. So it's necessary to hold together a bad design. If some jumps on one side, it must be clearly heard and felt on other side.
The subfloor is almost always continuous. It is a short circuit but there are practicalities like building integrity that cannot be ignored. There is typically gypsum underlayment to add mass to the floor assembly (stops at the inside face of the unit separation wall) and sometimes sound mat if not carpeted to reduce impact.
Redeye,
structures TRUMPS ( no pun intended) Acoustics I believe
Unit separation walls are fire partitions, not fire walls.
Combustible materials can go through fire partitions?
Yes kinda, it depends. Fire partitions begin at the top of the sheathing and stop at the underside of the sheathing. So the sheathing is not part of the fire partition.
Good Answer!