Ok, I added the PAX.mate material to both sides of my case since they come off very easily. The top and bottom of the case are riveted to the structure, and there isn’t enough room to apply the material from inside the case.
Anyway, having the PAX.mate material on the sides makes a big difference in sound. Unfortunately, I don’t have any scientific numbers like decibels before and after, but I have what counts the fact that I can hear the difference from what it used to be (headache causing, highpitched whine) to a (mild whine).
Right now the SCSI hard drives are really my noise causing parts. A Seagate 10,000 RPM 18GB drive and two IBM 15,000 RPM 18GB drives. There exist hard drive suspension parts, but they require using a 5.25"e; bay, which again I’m not willing to part with. I did add rubber grommets between the screws and the hard drive (as washers) which helped a little.
I guess the only real cure is to replace the SCSI drives with nice quiet SATA drives. Which means I’ll either need a SATA controller OR a new P4 motherboard. Hmm…