The problem seems to be a system issue rather than app-related, being reported in iTunes, QuickTime, VLC, Hulu, Vevo and when watching web videos in both Safari and Chrome – but doesn’t seem to affect all videos. It has also been reported that the issue persists when running Mavericks …
Several customers report that Apple is keen to get hold of affected machines so that it can identify the cause.
tbrumleve wrote: After being contacted by an AppleCare rep today, they do not yet have a fix. They are very interested in getting a hold of the affected hardware, and are willing to send a replacement immediately. However, they cannot guarantee it won’t have the same problem.
This is the second issue to reportedly affect the new MacBook Air, after widespread reports of wifi problems. In that case, Apple issued an update to the wifi software. However, 83 posts in a thread live for several weeks suggests that while the audio issue is affecting a significant minority of machines, it is likely less prevalent that the wifi issue.