[TenTec] Hercules II fan noise

[Steve Hunt <steve@karinya.net>]

I was trying to copy a weak CW signal yesterday, without headphones on, 
and noticed just how intrusive the sound of my Hercules II cooling fan 
is. I don't think it's any worse than when it was new - just that I 
happened to notice it more. It doesn't help that the moment the amp 
delivers any power - even as little as 40 Watts - the fan speed 
increases, and with it the pitch of the noise.
Is this normal for the Hercules?  Have I got a faulty fan (from new)? 
Are there alternative, quieter, fans?
Grateful for any views from other Hercules owners.

Steve G3TXQ