Cars of the future may be equipped with unusual warning sounds, ranging from cock crows to crashing waves.

Psychologists from Leeds University are testing the most effective "audible icons" to alert motorists to road hazards or mechanical faults.

They are experimenting with noises such as crying babies, ringing bells and footsteps on gravel, in a study funded by the government's Engineering and Physical Sciences Research Council.

Denis McKeown, the head of the project, said that using the right noise could improve drivers' reaction times. "We have to find out which ones convey the right degree of urgency and a commonly-understood meaning," he said. If the alarm was too unpleasant, motorists would disable it.

Tests so far have found that horn blasts are the most unpleasant, and the sea the least.

The findings will be tested in the next generation of in-car gadgets, notably collision detection systems, which monitor a car's speed and the distance from the vehicle in front and regulate braking.