I have a 2014 Pathfinder, with 180k miles. Recently it started to make a odd sound, it is hard to explain the sound, but the best way I can describe it is it sounds like a idling diesel engine running. I can hear it while in any gear and the sound does not change as I accelerate or deaccelerate. While the car is in park, the sound is the loudest at the drivers side floorboard. the sound appears to be traveling from somewhere, I do not see anything under the floorboard that would make any sounds. When I open the hood I cannot hear it. Anyone have any idea what it can be? I have a audio memo recording of the sound on my iPhone, but cannot figure out how to attach it to this post, anyone know how to do that?