Noise between headliner and roof near rear center window

Have this noise that's developed over the past month or so. When I go over a rough road, I get this deep hollow base type sound. Today I finally figured out where the noise is coming from but don't know how to access it. It's between the headliner and the roof next to the rear center window. When I press on the headliner, the noise goes away. I can't figure out how to access the space between the headliner and roof. I've tried removing the lens cover for the outside light but can't figure out how to remove the other part unless it's screwed on from the inside or something. I want to put some foam padding inside there to stop the noise if that's the problem. Anyone know how I can get access to this?

 

I think you need to remove all of the interior trim and then remove the liner. You could take it into a body shop and have them remove it.