Depends on what it was thinking about really. The really rapid clicking noise was generally the mechanical hard drive heads seeking and moving quickly. You could tell if it had been thinking too hard for too long when the mechanical drive sounded like it had sneezed quietly (I’m not joking), that’s when you started to back stuff up rather quickly.
The more single-tone longer-note experience was generally reserved for the floppy disks.
The quiet mechanical spin-up noise was often an optical drive spinning the media - usually a CD - up to it’s normal reading speed, and you quickly forgot about it.
If it sounded like it was thinking like a early morning bird with a hangover, they were reminiscent of the early 90min tape drives. More industrial drives didn’t make that noise thankfully.
The aircraft engine type noise was generally one or more of the case fans giving it some VTEC love to cool a component that was running hot, or if someone smashed the Turbo button.
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