Engine chirping noise

I am having a chirping noise I can’t seem to figure out. I have replaced the belt and the tensioner pulley. While the belt was off I spun the other pulley's and did not feel or hear any issues. I would like to fix it but it has been hard diagnosing where it’s coming from. Any ideas on what else it could be? When I get under the truck while it’s running it is much louder. Not sure if that would help. Any advice would be great. The more I listen to it it more sounds like it’s coming from the back of the engine or even below the truck altogether.