Weird & Something loud noise from engine

So it started couple days ago and it doesnt happen all the time, but today it did it for about 2 hour, when i accelerate the noise quiet down or stop, when the truck stop moving, it may start again and when the A/C is on its worse, for a moment the loudest was when the engine was at aboutr 1.5k RPM, i think it may start happen when the engine is above 200F. Then ive let the truck sit for about 2 hour, started again to go home but the sound didnt came back.

This video show when it was at loudest ive heard, normally its not that loud. Note that it doesnt exactly sounds like how i heard it. But similar.

I have no idea where it comes from. Its a ranger 2000 XLT off road package.

Anyone got an idea?

Thanks