When the vehicle is warm, it makes a loud, high-pitched whistling noise from under the hood. It sounds like a vacuum leak.
A vacuum leak is a possibility but another possibility would be an exhaust leak. Both can cause a whistling noise when the engine heats up. A vacuum leak is more likely to change with engine speed. A qualified technician, like one from YourMechanic, will be able to perform an inspection and a vacuum test to determine where the noise is coming from.