One more thing to watch out for at data centers - fire drills

Releasing inert gas from fire suppression units that were over
pressurized resulted in an extremely loud noise

My experience is only with in-specification systems (and only in tape libraries) but those tests were pretty loud.

– causing cabinets
> full of hard drives to vibrate – which got transmitted to the read –
> write heads of the drives.

My experiences were back in the days of washing-machine class disc drives and they were a 4-hour fire-wall away, but I don't remember them being impacted. (I can't believe that I was allowed to conduct a test with them running, but I don't remember shutting them down.)

I wonder if orientation mattered--mine were all platters parallel to the floor, I wonder if the damaged ones were parallel to the wave front.

If you watched the video of the guy who screamed at his disk drives to cause temporary faults, the JBOD had its platters horizontal to the floor.

One of the reason the washing-machine-sized CDC Storage Module Drives weren't affected by high noise level is the sheer beefy mass of the head assembly and the voice coil. Also, the track spacing on the platters of those drives was far less dense, so any noise-induced mis-tracking would be minuscule, and easily handled by said voice-coil's position-error system. The heads were larger, as well as the head arms. In this situation, mass is your friend.