3.0l engine in known for Cam Synchronizer issues, bushings wear out and common noise for this is high pitch squealing, often described as similar to fan belt squealing.
Good read here: Ford Ranger 3.0L Camshaft Position Sensor
If you are not sure where the noise is coming from you can loosen the fan belt on COLD engine, remove it from crank shaft, and then start the engine, none of the pulleys are turning now.
If you hear the squealing then it is for sure Cam Synchro.
Don't run the engine more than 2-3 minutes without fan belt, you can REV the engine to see if squeal starts