There will also be noise coming from the turning radiator fan and the belt(s) that turn the fan blade. There are a multiple of other belt driven devices under the hood. An engine pulley is mounted to the engine of an automobile and drives all belts. Your car probably has a serpentine belt which is a continuous belt used to drive multiple peripheral devices.
Those devices include an alternator, power steering pump, water pump, air conditioning compressor and the radiator fan. The belt tension and speed is guided by an idler pulley and/or a belt tensioner and or by repositioning the attached devices one direction or another to pull on or loosen the pull on the pulley.
Belt and pulley noise is usually a screeching sound that has a repetitive pattern screeching on each revolution. The screech can be caused by a worn out belt or by the pulley attached to an engine accessory that is starting to freeze up.