1. A system for determining a touch contact object type, comprising: a communication interface configured to: send a sent signal to be used to propagate a freely propagating signal through a propagating medium with a touch input surface, wherein the freely propagating signal has been allowed to freely propagate through the propagating medium in multiple directions to a plurality of receivers on multiple axes of the propagating medium; and receive a received signal detected due to a touch input object contacting the touch input surface, wherein the received signal includes the freely propagating signal that has been disturbed by the touch input object; and a processor coupled with the communication interface and configured to: compare at least a portion of the received signal with one or more signatures of one or more touch input object types, wherein comparing at least the portion of the received signal with the one or more signatures of the one or more touch input object types includes comparing a portion of the freely propagating signal that has been disturbed by the touch input object with the one or more signatures of the one or more touch input object types; and determine a type of the touch input object contacting the surface based at least in part on the comparison.