Verified answer

My system was doing this as well so I took it apart and cleaned it. It's like brand new now really quiet like when I first got it. I dont care about the warranty because Ive had it nearly 2 years now. This site was really helpful:

http://www.llamma.com/PS3/repair/PS3_disassembly_t...

Or if you want to keep your warranty send it to SONY or use a vacuum cleaner and suck out most of the dust. Also you can ramp up the fan. To do this turn the system off using the switch at the back. Whilst it is off hold the eject button and then turn the system on using the switch at the back. The fan will ramp up and spin really fast and hopefully blow out a lot of the remaining dust. Wait for the fan to stop and then turn it off with the switch again. This is also good for Discs that get stuck and wont come out.

I have a PlayStation 3 and it does this but not all the time, but if yours is doing it all the time,

I recommend that you make sure the vents are clean *do not use compressed air as it will just blow the dust further into the PS3*.

Oh and make sure it has enough ventilation space on all sides, I have mine about half a foot to a foot from a wall at each side.

If this continues, it might mean your PS3 is overheating, and you should get a red light or a yellow light indicating hardware failure.

Try cleaning out the dust. Get a low powered vacuum to suck the dust out of the vents.