ABSTRACT
We are able to hear and see objects in our environment when these objects interact with elastic, sound, and light waves. Even if our senses are not quite up to the task, we have ultrasonic sensors or infrared sensors that can be used to identify objects. Elastic waves are used routinely in seismic exploration and to determine whether complicated machine parts are in working order. But our senses, natural or artificial, can be tricked into making the wrong identification of an object because different material properties in an object can lead to the same behavior at a detection point.
