I am also experiencing this audio issue with 5.1.2. I reported this to Garmin via a Help Support ticket over a week ago. So far, the response has been incredibly poor and I seem to be getting nowhere. Even a request for a previous version of the software that worked was denied. This is concerning as my videos are often used as evidence in police matters. Garmin's brand has been severely damaged in my eyes.
athawk... the popping is introduced only when exporting from VIRB Edit. VIRB Edit 4.2.3 was the last version I had that exported correctly. (if I recall, this issue popped up in a prior 4.x version and was resolved. I think Wurth was aware of the fix back then) here is an example of the audio noise: https://www.dropbox.com/s/s19ycc1nr70rmch/virb-edit-audio-noise-test3.mp4
System specs: Macbook Pro Retina Mid-2012 2.7ghz Intel Core7 16gb / macOS 10.12.6
VIRB Edit 5.1.4 was just released this morning and should fix this audio issue you've been seeing (Thanks for the videos, they were very helpful!). Please tell me if this is not the case.