US Patent 10386968 Method and apparatus for active ultrasonic touch devices

A system for determining a user indication is disclosed. The system includes a communication interface configured to send a signal to be used to propagate a freely propagating signal through a propagating medium with a surface and receive the freely propagating signal that has been disturbed by a disturbance on the surface. The system also includes a processor coupled to the communication interface and configured to process the received signal to determine a user indication associated with the disturbance.