buzzing sound at times from regulator circuitry
The sound is probably coming from the inductor.

However, that indicates that the power supply control is going meta-stable.  The frequency of individual pulses should be way past what you can hear.  What you hear are oscillations of the control system.

Usually this causes no real harm, just a little drop in efficiency.  I see that this switcher chip doesn't have any external compensation, so there is nothing you can do to tweak the controller.

Make sure that instability isn't caused by bad or open C2.  That should be a ceramic mounted physically close to the chip.  If C2 is the electrolytic in the top left corner of your picture, then that's clearly bad.  Replace it with a ceramic, or possibly two in parallel, then next time pay attention to the recommended practices in the datasheet.