Aural sensor

Aural sensors were devices that could give audio simulations of the sounds of nearby spaceships' engines. This was done to give a spaceship's crew a rough idea of where surrounding ships were when they were not visible on the screen.

The Millennium Falcon was known to be equipped with such sensors.

Behind the scenes
These sensors were "invented" to explain why sound was heard in space in the Star Wars films, despite the physical impossibility of that (as there is no substance that can transmit airwaves). This phenomenon is seen in a number of science fiction films and games, not just the Star Wars ones, and is generally accepted as part of suspension of disbelief, as the audience would be left confused otherwise.

Notably, John Ostrander has expressed concern about the tendency to explain every single "unrealistic" detail, believing that these should be left for technical manuals and are not necessary in stories. 

Appearances

 * Star Wars Radio Drama