Recently on the scanner I heard two defect detectors at different mileposts and thought they were on the Winston-Salem District that is west of our house running from Winston-Salem north to Roanoke. Turns out it was coming from the K-Line that runs between Greensboro and Winston-Salem. I found this out by finally finding a timetable for the NS_Piedmont.
By the way I recently found this website about the Winston-Salem district which has an excellent overview of that line. http://pumpkinvine.wordpress.com/