In all the great sci-fi movies are unique and good quality sound effects. Sound effects that had to be created by house hold materials in some cases. For example in Star Wars IV: A New Hope, did you know that the famous gun blaster sound in the film was created by the head sound designer when he was out on a hike with his family? He had bumped into the guywires of a radio tower and it made this sound(http://www.youtube.com/watch?v=uLRPGFIl0Bs).
Sounds are everywhere, especially sci-fi sounds. Go outside one day and just listen. You will be amazed at the provocative sounds you hear or even in your house. But, don’t forget your sound equipment! Get everything on your mic and review the footage later. You will hear some amazing pieces of audio to put into your sci-fi flick and the best part of all is that these sounds are free!
Now, of course not every single sci-fi movie used everyday sounds for their picture. Star 
Trek got their sounds strictly with synthesizers. These synthesizers had many different levels of sound and made the sound effects quite interesting. Sometimes they were creepy, sometimes they were just plain weird. Today we have computers and what not to generate sound effects, but anyways those are the two schools of thought on sci-fi sound effects.
I learned that almost all sound effects in Star Wars were made from everyday things in our world!
link to article:http://www.videomaker.com/article/15352/