The original clips are fine. I exported this from Premiere CC (windows 7 desktop). The completed video had a few pops (digital noise). I have no idea why. I exported it again and then the new file was fine. But obviously I am concerned that this popping noise happened at 3 random places within a 1 hour and 20 minute teaching video.  It was a student who noticed it.  (and its a bit unprofessional). I cant check through a 1 hour video in its entirety each time.. as we do several videos per week. Has anyone got any idea how this may have happened? or is it a bug in premiere ? Here is a link to a short youtube of the 3 pops: https://www.youtube.com/watch?v=d_avkk0GAcs 

Hmm, I wouldn't describe that sound as "popping" -- popping usually means very short clicks -- it's more like short bursts of white noise. A quick search suggested that problems with audio in files exported from Premiere are not unheard of, but it seemed there was no one definitive issue, cause, or solution -- it'd depend on the particulars of the files, the project, edits, hardware, etc.. Suggestions included exporting in different formats [as a test], checking to see if the noises occur at edit/transition points of any kind, etc.. I suppose it could also be related to the versions of Premiere & the OS [you seem to be running a pretty old system there].. But if a second export was fine then it was probably just a little temporary glitchiness -- a hard computer shutdown/restart is always a good idea for unexplained problems. I would say that while I understand that you may have time constraints, as an audio engineer/producer who also does training videos I would never release anything without a thorough test playback. Of course that would only identify when there are problems not solve them, but at least you'd avoid releasing a flawed product. Maybe a trusted student or intern could check them for you?