Ok, this is very weird. The HD on my PC recently failed and since I don't need a huge drive, I took the opportunity to replace it with a SSD (flash). But I swear I can still here a slight sound when the PC is accessing the SSD. Today, out of curiousity I decided to investigate. The sound seems to be coming from the MB area, near the CPU. It's definitely not coming from the SSD. I downloaded a disk benchmark test. When the test is not running no sound. But with it pounding away on the SSD, there is this faint tingling, kind of metallic sound. As soon as I stop the disk test, the sound stops. I've also heard it when doing other disk intensive activity, like big file copy. It probably was there with the old HD too, but covered up by the sound of the HD.
I can't explain it. It's very bizarre. Since it's a faint metallic sound, seems around the CPU, could it be the heat sink? But I can't think of how or why that would be happening? There is a fan, but I stopped the fan and it made no difference.
Very happy with the SSD. My boot time went from 95 secs with the hard drive to 32 secs with the SSD.