Good Day,

I'm newbie here and newly mac user. Just encounter dunno if its a weird or what. Before audio on my iMac is working properly, then suddenly one day it doesn't work. Check the system and nothings change the IOAudioFamily.kext is still there. Try to update the OS still same and reformat it still my audio doesn't work. Thanks for the help more appreciated. If you needed more info or question to make it clear. My pleasure to reply. Thanks

Please excuse a simplistic question, but you mentioned having checked "the system" without mentioning that you took a look in /Applications/System Preferences > Sound to ensure that your volume hasn't simply turned itself off (as has been known to happen).

And since I'm here... Which specific iMac, which version of OS X, and are both your internal and external sound non-functional?