Ultrasound is used to determine, by echo ranging, the distance of objects in front of a user for allowing a visually impaired pedestrian to walk safely. A double circuit allows two simultaneous measurements. Distances measured are converted into human paces or steps. Then each ear of the human receives...http://www.google.de/patents/US6469956?utm_source=gb-gplus-sharePatent US6469956 - Ultrasonic distance detection for visually impaired pedestrians
