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 on my macOS High Sierra 10.13.6. Source of idea.
I'm using a 3rd party USB audio device for which I need to do this about once a day - ymmv on an Apple-only structure.
Launch Audio MIDI Setup, from /Applications/Utilities.
Window menu > Show Audio Devices if it's not shown already
Select your regular output device on the left - the one with the speaker icon.
Change the Format [either way] from 44,100 to 48,000 or vice versa. Wait 2 seconds, change it back.