Yes, much clearer. OK. How thick is the tile? You may want to double the 3/8" ply in the tile area to even the floor height. Most tile is roughly 3/8" thick and your hardwood floor is 3/4". I would screw every 1x6" board to the joists before you put down ply. Then glue and screw the ply down to the 1x6. You should eliminate all opportunities for squeaks this way.