Storyline 360 lightboxes and audio

I'm working with several slides with audio that jump to a lightbox when the timeline ends. I expected to have to use variables to keep the first slide's audio from playing again when the user closes the lightbox, but this doesn't seem to be necessary, at least in preview mode. And I can't find anything in any of the manuals that discusses audio playing and lightboxes.

In this project, there's audio on the initial slide and audio on the lightboxes. These are audio files recorded in Storyline. Otherwise, there are just standard objects on the slides. The trigger is jump to lightbox when the timeline ends.

Can someone confirm that variables aren't necessary to keep the original slide's audio from restarting? 

Thanks!