Lionel U.P. Excursion Train

I posted this topic on the 2-rail forum as well.  I just saw these cars in the new Lionel catalog and would love to run them on my 2-rail DC layout.  The trucks, wheelsets and wipers I can handle myself...but what about the two cars with sounds?  Would be nice to keep that aspect.  Will the sounds function on DC current, or only AC?  If the latter, is it practical to install a small voltage inverter circuit or am I overthinking this?  I would assume that the AC is eventually rectified at some point to run the electronics anyway.