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> In the 90's harddrives often had a 7200 Hz whine which was enourmously annoying.

The what now ? nothing in hard drive runs at that frequency

More like 7200 RPM, but that would be 120Hz. The motor would be driven by PWM though, that's more likely to cause sound issues

A deep dive into that topic...PWM drivers for hard drives, torque ripple, and reducing noise. https://www.ti.com/sc/docs/msp/papers/1998/bwhite.pdf