I am also running on an Air. I have not encountered that problem, sorry. MacOS sound system is sometimes quite flaky, so you can try running this in a terminal:
Code:
sudo launchctl unload /System/Library/LaunchDaemons/com.apple.audio.coreaudiod.plist && sudo launchctl load /System/Library/LaunchDaemons/com.apple.audio.coreaudiod.plist