At least in DC Metro area, whenever i have stayed out in VA near a Metro line (Braddock Road and Falls Church, both places where the line is above-ground), it's practically silent.
i lived a few blocks from the VRE station at L'Enfant Plaza when i lived in Southwest DC. Commuter trains are not loud like freight trains IMO.
but good luck conveying that to residents who are used to loud freight train locomotives :) i guess i don't blame them for not believing until they are shown. My house in Slidell is about a half mile from the CSX/Amtrak line and yeah, them freights are loud.