Connected RPI3 to hdmi soundbar - no sound

Hi all,

Been trying to connect my rpi3 to my HDMI soundbar. It works over HDMI with a monitor and also with an AV receiver. I believe it uses ARC when connecting to a TV.

I suspect this is something to do with the fact the soundbar isn’t meant to display image or something, not sure.

Has anyone experienced this or found any config settings that might make these compatible?

ALSO: Will the rpi 3 output audio over USB without some sort of soundcard