Sounds like a wheel bearing to me. Since you say it is louder when turning left, a good chance it is on the left. However, I don't know exactly how the bearing are on the F-150 so that could be deceiving (so I have been told on other vehicles that I had to have bearings replaced) if there are 2 bearings at each wheel. Assuming the bearing is bad enough, jacking up each corner of the truck to determine which wheel it is by turning and seeing if there is any unusual play. If it was me, I'd start with the left side.

 

Ok the noise could be a bearing !
You already did the 1st step.....driving the truck and determining where the noise is coming from.

If you turn right, you are taking weight and pressure off of the left side.
And vice versa.....
So if its louder when turning left .... it would be the right side !

The next step is jacking up the front end. ( don't forget jack stands!)
With the front end supported off the ground spin both front wheels while holding your hand on the coil spring....any grinding in the bearing will transfer to the spring and you will feel it with your hand.

This will confirm which side is bad.

Best of luck getting it figured out