What is the rattle sound in the fan.

From your description either the bearings are going out on your fan or you need to take the laptop apart and clean out the heat sink. Compressed air will only push things back into the fan. I suggest first you clean out the heat sink and test it to see if the problem is solved. You can find the service manual for dismantling your laptop and accessing your heatsink the at the HP support website, for free and downloadable in the HTML or PDF format. After you clean out your heat sink if the fan is still making noise you will need to replace it.