Is there a sternwheeler steamboat on the route, and is it playing something like Dixie? I recall a route that did, and you could hear it all over the route, nonstop. I edited the steamboat and then the sound file and set the volume to zero.
EDIT: It was this one: <kuid2:78193:924:2> Drivable Robt. E Lee Steamboat - 3m by cyberstorm.