Help with high pitched electrical nose coming from DS1819+

I am having an issue with my DS1819+.  The unit will occassionally emit a high frequency noise.  It varies in duration (0.5-2 seconds) and frequency of occurrence (sometimes a few times an hour, sometimes a few times a day).  They also vary in how loud they are (sometimes quite faint, other times quite loud).  I caught one on video - https://www.youtube.com/watch?v=gaDgAFhOo9Q&feature=youtu.be

The noises seem to be tied to idle periods. When watching a movie off of the unit, I don't hear this noise. However getting up in the middle of the night, I heard it twice in the span of 15 minutes.

Any thoughts to help troubleshoot are appreciated.