So, some more info:
xfconf-query -c xsettings -p /Net/SoundThemeName
env | grep GTK_MODULES
ls /usr/share/sounds/$(xfconf-query -c xsettings -p /Net/SoundThemeName)/stereo
which canberra-gtk-play
You may need to set SoundThemeName to 'freedesktop' and export GTK_MODULES=canberra-gtk-module:canberra-gtk-module
So, some more info:
xfconf-query -c xsettings -p /Net/SoundThemeName
env | grep GTK_MODULES
ls /usr/share/ sounds/ $(xfconf- query -c xsettings -p /Net/SoundTheme Name)/stereo
which canberra-gtk-play
You may need to set SoundThemeName to 'freedesktop' and export GTK_MODULES= canberra- gtk-module: canberra- gtk-module