Getting hard drives to be quiet: an analysis

Regarding our previous coverage of the MacAAM program (see one and two), Eric Carlson tested the effects of MacAAM his G4 with two IBM drives; a stock Apple 20GB IBM 5400 RPM drive as slave and a 75GB IBM 7200rpm as the master on the internal ATA-66 bus. He also confirms some details describing the underlying process. He writes:

"The AAM program appears to change the Acoustic Management properties on all drives on the IDE bus, not just on the Master drive (the one it reported), since both of my drives were noticeably quieter after selecting the quieter (128) mode. After doing some digging on IBM's site, especially here, and reading the documentation for their IBM Feature Tool, it appears the AAM feature switches between Quiet Seek Mode and Normal Seek Mode. This makes sense based on what a reader reported today and my own experience. After selecting the quieter mode, the disk seek noise is nearly inaudible over the fan noise. Specifically, AAM reduces the seek noise, ie. the clicking sound, but not the whine of the spinning drive. It appears to do this by increasing the seek time of the drive.

I decided to quantify this speed reduction, so here's a semi-scientific look at the only benchmark tool I have that tests seek times, the ancient Time Drive utility (v. 1.3) from La Cie circa 1991:

This data is after 4 previous passes on a 4000k file to avoid any possibility of cache interference:

AAM=128 (quiet mode)
Pass 5:
Latency = 0.24 ms . . . . . . . . . . . . . . . . average = 0.23 ms
Ave. Seek = 9.10 ms, (access = 9.34 ms) . . . . . average = 9.14 ms  <--Note!
Max. Seek = 0.00 ms, (access = 0.24 ms) . . . . . average = 0.00 ms
Write transfer rate = 35108 KBytes/Sec. . . . . . average = 34133 KBytes/Sec.
Read  transfer rate = 30720 KBytes/Sec. . . . . . average = 30720 KBytes/Sec.
Simulated "Typical" rate = 1572 KBytes/Sec. . . . average = 1350 KBytes/Sec.
AAM=254 (normal mode)
Pass 5:
Latency = 0.23 ms . . . . . . . . . . . . . . . . average = 0.23 ms
Ave. Seek = 7.10 ms, (access = 7.33 ms) . . . . . average = 7.48 ms  <--Note!
Max. Seek = 0.00 ms, (access = 0.23 ms) . . . . . average = 0.00 ms
Write transfer rate = 35108 KBytes/Sec. . . . . . average = 32336 KBytes/Sec.
Read  transfer rate = 30720 KBytes/Sec. . . . . . average = 30720 KBytes/Sec.
Simulated "Typical" rate = 1455 KBytes/Sec. . . . average = 1394 KBytes/Sec.

According to these results, the average seek time on a 75GB 7200 rpm IBM Deskstar is slowed by a bit over 1.6ms (22%) when in the quieter AAM mode, while transfer rates, etc. stay about the same. Is this noticeable? Maybe, to some users. I could detect the change it in some operations, such as opening Finder windows with large numbers of icons."