Playing music on YouTube in Chrome did not output any sound. Playing video files with Quicktime and VLC didn't work. I noticed this problem before and it fixed itself after a restart. But I wondered if I could reset a process to get audio back.
coreaudiod process might work (it did for me). One way to restart it is to launch Activity Monitor, then View->All Processes, scrolling down to
coreaudiod then clicking the big
X button to force quit. It gets relaunched automatically.
Another option is at the command line:
sudo killall coreaudiod
After doing that and refreshing the Chrome tab - audio output works again. Source of idea.