A system is for detecting a location of a touch input on a surface of a propagating medium. The system includes a transmitter coupled to the propagating medium and configured to emit a signal. The signal has been allowed to propagate through the propagating medium and the location of the touch input on the surface of the propagating medium is detected at least in part by detecting an effect of the touch input on the signal that has been allowed to propagate through the propagating medium. The system includes a piezoresistive sensor coupled to the propagating medium. The piezoresistive sensor is configured to at least detect a force, pressure, or applied strain of the touch input on the propagating medium.