I just bought 3 of those Antec smart fans. They're anything but loud. Maybe yours is out of balance. They're only 34.5 dBa at their loudest which is pretty quiet.
There's no way to adjust them. The speed is controlled by the temp.
You should only use these fans as an exhaust fan - the temp sensor will be defeated if you use them as an intake (it'll only detect the cooler air being sucked in from outside).
I'm using one as a replacement for my PSU exhaust fan which was VERY loud. I'm also using one on my AX7 heatsink. They're definately quieter than what I had in there before, and they get even quieter when I put the system into sleep mode at night and it cools down.
You only need to connect the 4 pin connector to a HDD power cable. The 3 pin is just for sending RPM sensor data to the mobo using one of the mobo fan connectors, but you don't need to use it for it to work.
In the package that the fan came in is a chart that shows the RPM versus temperature. I have a copy posted
HERE