On Thu, 18 Nov 2010 18:48:09 -0600, Ignoramus5827
wrote:

I have a couple of devices with very noisy and annoying fans. One is
an old laptop and another is a car inverter. In both, fans make a very
annoying, inconsistent, and rattling sound. Before taking those things
apart etc, I wanted to double check what is the typical cause of this
and how to deal with them.

i

If I'm going to bother taking them apart, I replace the fans with new
ones of similar size and rating (but often higher quality), from
Digikey, Newegg or whatever.

To some extent, if you have high airflow, you will get noise, but some
real industrial fans whine like little jet engines when new, and are
are unsuitable for an office or home environment.

The rattling is usually an indication the bearings are shot. I've not
had much luck with oiling them, the fan quits again soon, and a bad
fan can shorten the life of the device (it's often the initial cause
of PC power supply failures, which leads to overheating, then a
semiconductor gets smoked).

The sleeve vs. b.b. choice is not as clear-cut as it once seemed, from
what I've seen. Quiet life of each may not be that different.