An input device outfitted with one or more ultrasonic transducers can determine the location of one or more objects in contact with the input device. For example, the input device can include one or more transducers disposed in a ring around the circumference of the input device or in an array of rings along the length of the input device. The ultrasonic transducers can be used to detect the position of the one or more touching objects in at least one dimension, for example. In some examples, the one or more ultrasonic transducers can produce directional ultrasonic waves.