See attached photo: you have a bad color wheel----it turns at about 12,000 rpm and bearings in the tiny motor go bad.
High pitched or fan like sound is classic symptom.
The wheel is available on the internet and You Tube has video instructions by model number for replacing it---Google the model number for the part number for your set to locate the part and instructions.
This for most people is a do it yourself job---takes like 45 minutes start to finish.
If color wheel slows too much set will shut down as its speed is monitored and the wheel can even shatter causing shutdown of the set.