Engine Vacuum Leak Step 2 - If a battery connection becomes corroded or if the battery is starting to fail, it can cause the alternator to overwork which creates a whistling, whining style of noise. Learn more
Battery Corrosion NON ENGINE PROBLEM - When a door seal fails it can create a whistling noise as air enters the passenger compartment, these whistling noises can be difficult to find. If needed have a passenger ride along while running their hands along the area the noise is being generated from, this will pinpoint the location.
Door Seal Helpful Information