Did some further checking on my alert sound problem. Found following error message in KM Editor log associated with the alert:
2015-10-25 10:06:54 ERROR: Preference shared sync write failed
So I went into KM preferences and unchecked the Sync Macros check box. Then re-checked it and selected the existing sync file which was in my Dropbox folder. No more errors in the Editor log and no alert sounds when I edit a macro. Weird!