The pilot's headphones will have a 3-D sound system so that the voice of another crew member will seem to come from that person, to avoid confusion. Audio "earcons" will signal certain events — a sucking sound will warn of fuel exhaustion, for instance. Speech input will be used to control non-essential systems.

At Rank Xerox EuroPARC in Cambridge, England, the emphasis is on creating auditory icons, or "earcons." The sound of approaching footsteps, for example, indicates that someone is about to open a dialogue with you on a computer network.

He is editing a special edition of the journal Human-Computer Interaction, on the use of non-speech audio in the computer's output. Small but meaningful sounds have become known as 'earcons,' by a punning analogy with 'icons.' To those who doubt their importance, Buxton says: 'all you have to do play a video game like PacMan. Turn the sound off and your score will go down. It clearly contains information that is valuable.'