I have a 2007 GMC Envoy that has a very loud and annoying high pitched squeak. The performance and handling do not seem to be affected so I do not think it is serious. But it is loud enough to get on everyone's nerves when riding in the vehicle.I have raised the hood but can not seem to be able pin point the issue.
If the noise is present when engine is started and increases with engine rpm, that would most likely from the drive belt related components. You would need to located the source and a hose as stethoscope would be helpful.