The first shot of the film is a representation of an asteroid or meteor hurtling thru space, apparently towards earth.  Although the musical score is dramatic at this point, we were looking to add something etherial and strange, as this shot sets the tone for the film.

Is their sound in space?

The sound effect heard are radio waves that NASA’s Cassini spacecraft detected near Jupiter, in the thin gas of charged particles that fills the space between the Sun and its planets.  The waves are in low radio frequencies, which have been converted to sound waves to make the patterns audible. 

The sounds are oddly like our creatures that appear later in the film....

Almost every scene has some sound effect added, to hide the ambient city noise or to embellish the emotion and content.

A persistent squeak inside the jail is characteristic of a small town that is slightly behind on its maintenance, and that feeling is echoed in the slight squeal coming from the Sheriff’s car brakes.

The pin ball machine in the diner was not working, so the sound effect was added.  Traffic outside the diner location was loud and inconsistent, so truck horns and auto pass bys were added. 

Other added atmospheric effects include the original recording of War of the Worlds radio play, featuring Orson Wells, and several selections of stock music, heard in the diner.