Why does my 3 V EL inverter make sound?
I presume your inverter is operating at an audible frequency. If your transformer or inductor has multiple parts it could be one part moving relative to the other due to the magnetic forces or the magnetic materials changing shape due to magnetostriction. The usual solution is to increase the frequency to beyond the audible range, i.e. > 20 kHz. Regarding the perceived direction, could it be that the wavelength is short enough relative to the spacing of your ears for there to be ambiguity? ~23 mm at 15 kHz.