so there's not much vibration to dampen
I beg to differ on this. You are right if you are saying the grommets don't do as much as suspensions (homemade or novibe), which I agree totally with. But this statement I disagree with... Seagate's white paper on HDD noise
is a must-read for hardcore silencers. It says:
"a drive that sounds quietest while suspended in an acoustic measuring chamber may actually sound louder when mounted in a system, while a drive that sounds quietest when in a system may not be the quietest when tested stand-alone. Several factors contribute to this disparity, including prominent tones, structure-borne acoustics
, measuring techniques, objective measurement versus subjective hearing and so on. (emphasis mine
"Seagate has considered the total effect of drives on a PC system and can show that structure-borne noise is the dominating source of disc drive-induced PC acoustics. In fact, testing has shown that changes in stand-alone drive acoustics had little effect on the overall system acoustics when drives were hard mounted in the chassis...
"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."