the sound you are describing is almost positively indicative of a front wheel bearing. the bearing is likely the front passenger side as the noise goes away when you turn right and UNLOAD the weight off that tire.
Verify (possibly) by lifting that side of the car and grabbing the tire at 12 and 6 oclock and pivoting in and out. if you get any wiggling, you definitely have a wheel bearing issue, though a failing bearing CAN AND WILL fail without making noise OR allowing any play in the tire!
Edit: check out the Duratec Maintenance forum, and read the "read me first" thread for a how-to on bearings, and a list of all possible repair options.