The whine is coming from the onboard speaker not the scsi drive.   Its because the caps are bad and the goo had leaked all over.

Its a pretty common problem across all the LC machines.  I II III.  here is some info to help you re-cap that.

http://maccaps.com/MacCaps/Capacitor_Reference/Entries/1990/10/15_LC_I%2C_II%2C_III_Power_Supplies_2.html

if you plug in some headphones you should still hear the same wine. or if you pull out the Fan/speaker assembly with the computer on. you will notice the noise will go away as well.  but all in all it needs capacitors pretty bad.