An ultrasonic touch sensor includes a touch structure having a touch surface with a plurality of sensitive areas, a pixel array of capacitive ultrasonic transducers, and a sensor circuit. Each pixel includes a respective ultrasonic transmitter and a respective ultrasonic receiver and is configured to monitor for a touch at a respective first sensitive area and at a respective second sensitive area. Moreover, each pixel is configured to generate a measurement signal that is representative of a first respective ultrasonic reflected wave reflected by the touch interface at the respective first sensitive area or that is representative of a second respective ultrasonic reflected wave reflected by the touch interface at the respective second sensitive area. The sensor circuit is configured to determine whether the measurement signal of a respective pixel corresponds to the respective first sensitive area or to the respective second sensitive area associated with the respective pixel.