Issue with the software driver, not sure why it happens but until Apple fix it, here is a fix:

Open Terminal
Type: sudo killall coreaudiod
Enter Password.
This will reset the audio driver and fix the issue.

IF after doing this you have NO AUDIO it just means the driver service didn’t restart so do the following first:

Open Terminal
Type: sudo launchctl start com.apple.audio.coreaudiod
Enter Password
This will manually restart the driver service

IF after doing this you STILL HAVE NO AUDIO, restart the machine.

IF it’s still not working, reset your PRAM and SMC - Google how to do this.

해도 좀 있으면 다시 난다
애플이 문제