What about sound for the movies?

Since this is just a screen, the sound depends entirely on the technology of the projector or the originating source (TV, laptop, tablet, smart phone, iPad, cable, satellite, DVD, blue ray, etc.)

You can use the native speakers of the source or you can hook-up additional speakers to a projector through either a DC jack or in/out cables.

For more information please check out our guide setting up a great backyard setup
http://outdoormoviehq.com/ultimate-guide-to-outdoor-movies
Or take a look at our recommended projectors and screens
http://outdoormoviehq.com/outdoor-movie-screens