I just returned from my anunts home down in OK, last week and the last time I was there I found several code violation and basically saved my Anunt & uncles lives, this time around I was there and the filter needed to be replaces as I noticed the airhandler running more than normal and working harder than it needed to so I checked the filter and sure enough it was way past due, what a difference that made. Now after changing the filter I also noticed the airhandler is quite loud even in low fire and low fan speed operation, the airhandler sit up on a box in a closet and the box (return air) is about 3' sq and 3' high which is directly opposite the intake grille on the other side of the wall and all supply air is ducted in the ceiling but the unit is just way nosiy IMO. Would the use of turning vanes help there situation or would they need to have some work done in the return box which the bottom of the airhandler sits directly on the top of this box ? Suggestions ? The stat is one of those lennox type, and I believe there system is one of the top of the line airhandlers/HP's.