3-D sound picture for the blind

  Polaroid Land use an ultrasonic auto focussing system. They also sell this alone as an experimental kit.
  If two of these can be used on the whitcane used by the blind or on a helmet that the blind can wear, it should be possible to produce a stereo sound 'Image' of the surrounding. A far away object can produce a lower volume signal while a nearer one produces a higher volume sound. A larger object can produce a lower (Bass) note while a smaller object can produce a higher pitched sound. Even moving objects can be detected by adding a Doppler shift. An object going away will produce a descending scale, while an oncoming object can produce an ascending scale.
  Microprocessors are quite cheap. Single chip audio amps are in plenty. All components are freely available.
  It should help a lot of blind people to get a better "view" of their surroundings.
  Since some of the objects themselves produce sounds, and this intereres, it is a simple matter to wear a pair of ear phones that get their input only from the sonar echo sounder.