How to prevent external drive from spinning up? Or, fastest quiet drive on spin up?

Question

My external drive insists on spinning up often without reason, often for open/save dialog boxes.  The spin up takes time and the computer is inoperable until it completes the spin up.  As a fast touch typist, who often hits command-s to save documents in Word, this is really a nuisance.  This happens with a USB and Firewire external drives.  It seems to be a feature within the OS itself--and likely some other programs in the background--that want to access drives. 
Is there any way of turning this behavior off?  For example, telling the OS to spin up the external hard drive only for a specific application (Carbon Copy Cloner).  So far, the only solution I've come up with is to eject the external drives, which isn't much of a solution if one wants automatic back ups!
Now, if there is no way of turning this off, are there drives that spin up quickly?  This USB drive I have takes forever compared to the Firewire one, which also takes too long.  At the same time, though, the USB drive has the blessing of running silently whereas the various Firewire drives I've had are noisy (with high pitched hums) even when idle.  (I realize that the noise has more to do with the enclosures, fans, heat sink, etc.) 
Quiet matters most, so if necessary, I'll just keep the external drives disconnected.

Answer 1

In the Energy Saver pane of System Preferences, make sure "Put the hard disk(s) to sleep when possible" is not checked. This will keep your external drives spinning, so you won't be delayed waiting for them to spin up.
"I realize that the noise has more to do with the enclosures, fans, heat sink, etc."
Yes, many if not most enclosures amplify whatever noise the drive inside makes. Your desk or table may also serve as a sounding board for your drives. Setting them on something that absorbs the vibration can help, as long as you don't obstruct any cooling air intakes or outlets.
Right now, your external drives are spinning up whenever the OS is asked to display all the possible places for things to be found or stored. I don't know of any way to limit that behavior other than unmounting the disks you don't want displayed.
Spinup time is generally shorter for 2.5" drives than for the much heavier 3.5" drives — there's just less inertia to overcome as things get moving. And 2.5" drives can also be quieter, because less mass is spinning and any tiny imbalance that might cause extra vibration is correspondingly less significant.