The bank was testing an electronics-safe fire suppression system in the main data center, but a pressure discrepancy caused the system to emit a loud noise while expelling inert gas. According to the bank, the sound was measured a over 130dB -- apparently loud enough to knock the HDD's physical components out of alignment.
That makes sense, but why hasn't something like this happened before? In a paper about hard-drive fragility and fire suppression systems, IBM researchers blame the march of progress: "Early disc storage had much greater spacing between data tracks because it held less data," The paper reads. "Which is a likely reason why this issue was not apparent until recently." Modern hard drives are less tolerant, and will fail if its read/write arm nudges 1/1,000,000 of an inch off of its data track. Good to know for folks building data centers with potentially loud fire suppression systems -- but maybe this is just yet another sign that solid state storage is the future.