Which drive noise is the most noticeable???

[LongRunner]

(The poll is about drives with fluid-dynamic bearing motors.)

Whoosh: caused by turbulence within the drive
Whine: usually emitted from the spindle motor coils
Seek: self-explanatory
Vibration: coupled through the mounting; extremely variable

This is not about any individual drive, but a generalisation of the drives you've had experience with.

[c_hegge]

It's always the seek noise for me (with the exception of older Ball Bearing HDDs, where it's the whine)

[LongRunner]

(As I didn't elaborate in the first post...)

For me it's usually seek noise, followed by whine and vibration, with whoosh/hiss last. There's a big difference in seek noise between single-platter and dual-platter Barracuda ATA IVs, between the ST340014A and the higher capacity PATA 7200.7s, and between those and their SATA counterparts. (Anyone have experience with the 40GB SATA 7200.7???)

For me, the choice of whether or not to use AAM comes down to whether the noise reduction is worth the performance trade-off. Some drives (e.g. WD800JD-00LSA0) are so quiet already that it's debatable whether it's worth using AAM on them. Of course, there are also drives that you wish had AAM - the SATA 7200.7s for one, and my ST31000528AS with firmware CC38 is weird. You can set "AAM" on it, but it doesn't actually control anything.

[shovenose]

It's usually the 7200.10-7200.12 Seagate drives where the seek is extremely obnoxious.
The older WD Drives (think IDE) were the ones that now whine obnoxiously.