Question about T43 fan "sound"

[ARD]

I bought a used T43 that is still under warranty.
I am aware of the T4x fan issue.
My question is about the actual type of noise the fan makes.
My fan makes a quiet slowly pulsing brrrr sound.
Like a fat fly sound.
Its not loud, it just buzzes softly.
Is this the normal sound it should make?
All you T43 owners chime in, please.
For reference, I have an A31 which is absolutely quiet.
So I'm kind of leaning towards the "its not a normal fan sound".

Thanks.

[xiong]

refer to
http://www.thinkwiki.org/wiki/Problem_w ... 29_problem