Fixing squeak in subfloor
Two long for a comment, Fully agree with shims and glue. I wish they had Gorilla glue when I was building, that stuff works really well as it expands and then gets hard so for some areas that's all that may be needed. The wood needs to be dampened with water first for gorilla glue to work. I have used it on a 2 story home the owner did not want to open the first floor ceiling. I drilled through the floor in several places above the joists dribbled a few drops of water in the holes and once the water soaked in filled with glue, after the glue was dry I cut the tops of the holes where the glue expansion bubbled up. Worked great but you will need to find the joists. There should be a joists because 24" would be the max spacing. My only other guess would be a change in direction of the joists.