Maybe do an RTA measurement and watch to see changes in noise floor. Or when you do measurements set REW to perform and average multiple measurements.
Just wanted to write the same... an open door or window in the measuring room does influence the low end. If I remember right, quite similar to your curves. Depends on room size, position of the opening etc.
I close doors and windows if I want compareable measurements in a room.
I close doors and windows if I want compareable measurements in a room.
If the pivot is at the low pass filter cross point Id suspece loose or broken connection. Otherwise, doors being opened and closed