Chosen Solution
Have the same problem on a 2010 white plastic macbook running high sierra. Nothing I found on line worked. Then one day I booted it from a Linux Ubuntu install USB stick and the sound worked fine all the whie that OS was booted so mine is not a hardware problem. It went back to silence when I rebooted into High Sierra. Does that tell anyone here what needs to be fixed on mine? thanks djc
Apple killed the startup Chime on you! Here’s more on it How to resurrect your Mac’s startup chime
