Re: Missing a few key points here
> It was generally known that the noise from gas fire suppression systems can damage hard drives, but not sure it was well known.
Yupe, well known indeed, e.g.:
Zurish Insurance: http://www.zurichservices.com/zsc/reel.nsf/b777a8062cedf191c12571fe00467717/6361b933b360dbac862584790079666a/$FILE/rt_fixed_fire_protection_data_centers_and_HDD_noise_sensitivity.pdf
3M (competitors to Halon systems): https://multimedia.3m.com/mws/media/1180481O/clean-agent-system-noise-hard-disk-drive-hdd-failure-faqs.pdf
I seem to remember reading an article somewhere (maybe even on TheReg) about someone (re)designing fire supression output baffles and also having design software to optimise their placement within DCs to eliminate the risk to HDDs. After a quick search all I can find (not the article I'm thinking of) is this:
https://solarfiresystems.com/news/silence-is-golden