I recently bought some woodland scenics track bed and as my wife was helping me with my layout asked what it was for. I responded that it is to keep the train noise down, but then I started thinking about really needing it. When I first laied out my track I tacked it to plywood to look for any potential problems with my layout. I ran the train for a little while and it really didn't seem that loud. So is it really that important? What does it really do? Do I really need it? And will I need to lay it under all the track - like rerailers and viaducts?