Well, here's the link to SpeedFan
Install it, and run it. I just installed it here - it took a minute to recognise all my fans, and then apparantly you just change the fan speed by using the up and down arrows for each fan (named Speed01, Speed02 etc.).
It took me a minute to figure out which fan was which (for example Speed03 ended up being my top fan) - I just temporarily put each one down to 0 and watched to see which one stopped.
So, to achieve what you want, presumably you just put down the percentages of yours fans, and they should quieten as you do so (unless they turn out to be fairly
Edit: Oh, and I really recommend you don't touch any of the other settings. As the program says, it could damage your computer if you do so.