I recently remodeled my apartment. I replaced the old plaster ceiling, which had a big hollow space between it and the floor above. Prior to replacing the ceiling I could hear someone walking above which annoyed me but was not a big deal; I could not hear voices from the apartment above. Before I put up the new ceiling I put up two layers of Rockwool Safe 'n' Sound 3 in. acoustic insulation. I put up two sheets of drywall with Green Glue Noiseproofing Sealant between the layers. There are recessed lights in the ceiling.

Now both I and my upstairs neighbor can hear conversations through the ceiling/floor. I do not know how the sound is passing from one apartment to the other. I would appreciate any suggestions for ways to diagnose and fix the problem. Thanks!