Were you hearing the sound before or after you had the tires rotated to the front?
It seems to me that what you're hearing is the brake booster working for either ABS, TC, or ESC.
If you're turning and going over a bump at the same time, its possible that you are triggering the sensor and what you're hearing are the brakes pumping the front wheel.
In almost all vehicles now with traction systems, they are brake based and people really need to take care of their brakes in order for these systems to function properly. If this noise is new, it may be worth taking to a garage for brake service. If there is air in the brake lines, or if your brake pads are worn too far down, it is possible for the system to be making more noise than necessary.
I'm fairly certain that if something was actually wrong with a sensor, it would trigger a service light and a trouble code.
Best of luck to you.
2011 SES 5spd #006 >> SR #213
Join the cause! 3 Door Fords for America! facebook.com/3DRS4US
What other people think of me is none of my business.