Here's a white paper from the world's biggest HDD maker -- Seagate -- on HDD Acoustics
. (Note: The Seagate's site has recently been changed; this very informative paper is no longer publicly linked there, so save it if you want to go back to it.)
Seagate has made significant progress in the area of isolator design and development. Isolators are mounting mechanisms made of a softer material than metal; they are used to separate, or isolate, the drive from the chassis, minimizing the transmission of structure-borne vibration and noise.
At one time, years ago, isolators were thought to be impractical for disc drive mounting; the frequent long seeks could induce excessive drive motion through isolator "wind up" and "release," which caused settling problems during seeks, which could in turn reduce drive performance and/or data integrity. Current drive designs, combined with Seagate's research and development of new isolator materials and designs, have largely eliminated these issues. In typical PC applications, over 90 percent of all seeks occur within only 30 tracks, which is less than 1/4 of 1 percent of the drive's tracks, inducing very little motion and wind up. The materials Seagate recommends for isolators are highly damped rubber compounds, which minimize the possibilities for wind up, amplification and other unstable conditions.
Our testing indicates that WinBench scores (industry-standard drive benchmarks) are not affected by mounting drives using isolators. Further testing beyond the bounds of common disc drive functions did reveal that when performing high numbers of long seeks (long seeks are becoming more rare as track densities increase), write performance could be somewhat reduced, while read performance remains unchanged. Again, most drives perform many more reads than writes, so that overall performance, even in these extreme circumstances, is not perceivably affected.
I had two Seagate Barracuda IV HDDs suspended in elastic for over four years w/o any problems from either. The 40GB discs are too small for my needs now; they are floating in the lab, still functioning fine.