The whirr sounded like fan noise and neither disc-player noise or hard drive noise. When switched on from cold, the noise was not present until 10 / 15 mins into the movie. I would expect noise from the disc to be a constant from the start. The key point is that the increased fan noise was accompanied by increased air-flow. I have a replacement unit now and it seems to be an improvement, but it's early days.
A agree that lots of other AV equipment has fans. However, it seems there are a quite a few PS3s which are extraordinarily noisy. Apparently, there are a number of substitute component parts which are put into some machines and not others. The point being, not all PS3s are made from the same components and consumers don't have an easy way of telling them apart. One example:
My original was louder than a home projector, for instance. I took the unit to a friend's house to get a perspective in a different environment, and his IN74 projector was quieter than the PS3 when plaved side by
The point of caution is that I wanted to share with people that if they are concerned, they should do a little more of their own research first. Many reviews declare the PS3 to be whisper quiet. If, as I did, you read these reviews, and speak to a few friends - and they all say the same, it's easy to draw the conclusion that complainants are speaking from a subjective viewpoint and are just too fussy. Yet the fact that same product is being made from different parts and there are accounts of differences in performation shouldn't be ignored if you're bothered about background noise.
HMV replaced mine without any concerns. Now I said the replacement is better. But, I have not yet performed the latest software update, which is another story and some believe that software changes are modifying fan settings. Given that the replacement is very likely to be from the same batch, I'm probably going to find this out the hard way.