Ventriloquist Horn

The roads in my part of the world are narrow, crowded and filled with people whose one mission in life seems to be to make life miserable for drivers. They only give way when you are about to run them over - and if one gets confused and jumps the wrong way, you have to be quick on the brakes. Come to think of that, that is how I walk, too. No footpath.

Enter the ventriloquist horn. Using advanced wave shaping technology and an array of piezoelectric speakers (paint on speakers - link) the horn is made to sound as if coming from a point just behind the victim, who then skedaddles off the way pronto.

The entire frontal area of the car, except the glass, is a giant array of piezoelectric ultrasonic transducers. They are driven with controlled phase such that the ultrasonic energy concentrates to a spot some three car lengths in front of the car. The ultrasound is modulated with a pulse rate appropriate to the pitch of the car horn.

The concentrated ultrasound heats the air which expands and produces sound according to the modulation. Since this virtual horn moves through the air with the motion of the vehicle, it seems to an unwary pedestrian that he is about to be run over - when you are, in fact, a comfortable distance away.