THX is a sound system standard brought about by George Lucas of Lucasarts fame and developed in 1983. Trademarked and noticed everywhere for it's deep, high quality tone at the beginning of most audio enhanced movies, THX has become a name (and sound) instantly recognized by most.
THX has become the name of high fidelity sound replication for movie theaters, home theaters, computer speakers, gaming consoles and car audio equipment. The initial goal of THX was thought up by Tomlinson Holman of Lucasarts so that George Lucas' third installment to the Star Wars saga, The Return of the Jedi would sound as it should in whatever venue it was viewed.
Although some would think THX is a recording standard, this is not true. THX is merely a quality assurance specification for the likes of Dolby Digital, SDDS, etc. Its a guarantee that when a film leaves the editing room and shown in a THX certified theater, it will sound exactly as the audio engineers of the film intended it to.
The THX standard is now licensed by THX Inc. out of San Rafael, California. This organization ensures theaters are fitted with the proper baffling equipment to deliver THX quality prior to being certified.