The room is ringed by a soffit both for acoustic and cosmetic reasons. A 1x4 was first attached to the wall and ceiling with adhesive and molly bolts. 3/4" MDF was then screwed to the 1x4s to create the soffit. The bump in the corner is due to a HVAC vent. If I had been paying better attention during the HVAC rough-in I would have run it down a different joist bay and wouldn't have needed to create the bump out to accommodate the vent box.