The sounds heard in the movie theater are not actually from "Star Wars".
Eric is seen holding Luke Skywalker's lightsaber from "Episode 6: Return Of The Jedi" in his dream. This lightsaber would have been highly unlikely to have been dreamt up during the time setting, since "Return of the Jedi" was not released until 1983. It is not entirely impossible though, as Obi-Wan Kenobi wields a lightsaber with a very similar design in the 1977 film. However, the fact that Eric is dreaming of himself as Luke Skywalker makes this possibility even more unlikely. And thus, said lightsaber is still very out of place in Eric's dream.