An ultrasound input device can be coupled to a material layer having an external surface located opposite the material layer from the ultrasound input device. The ultrasound input device can transmit an emitted signal through the material layer towards the external surface and receive a set of reflected ultrasound signals associated with the emitted signal. The set of reflected ultrasound signals comprises at least one reflected ultrasound signal, and the set of reflected ultrasound signals can be associated with a touch event between an object and the external surface. A system can comprise one or more data processors configured for performing operations including determining an energy signal associated with the set of reflected ultrasound signals, extracting feature information associated with the energy signal, determining an inference associated with the object based on the extracted feature information, and generating an output signal associated with the determined inference.