Belt Squeal
WARNING: This page is about a different car, the 2007 Ford Pickup, 2007 Ford F550 Super Duty, 2007 Ford F450 Super Duty, and 2007 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
Belt squeal is a high frequency air-born noise generated by accessory drive belt slippage on the power steering (P/S) pump pulley. Squeal increases with system loading and at the steering stops.