Yes. Just specify the audio stimulus first with a Time value of 0ms--that indicates no delay between the onset of the audio and the next stimulus. Specify the next (visual) stimulus. Voilà. Check out compound screens in the Input section of the user's guide, or online here:

www.empirisoft.com/directrt/help/directrt_time.htm
www.empirisoft.com/directrt/help/directrt_samples_compound_screens.htm