Released at the same time as the subject of this topic:
Empire: http://www.lddb.com/laserdisc/31581/PILF-1318/Star-Wars:-The-Empire-Strikes-Back-(1980)
Jedi: http://www.lddb.com/laserdisc/31582/PILF-1265/Star-Wars:-Return-of-the-Jedi-(1983)
Do we know anything about the tracks on these discs? According to LDDB, they do both contain digital sound.