An ultrasonic gas leak detector system for locating a source of ultrasonic airborne energy is described. An exemplary embodiment includes a plurality of spatially separated ultrasonic gas leak detectors, each configured to generate signals indicative of detected angles of arrival of received ultrasonic energy at the respective detectors. A locator processor receives the signals generated by the detectors, and is configured to process the signals to determine a location in three dimensions of the source of the ultrasonic energy received at the detectors and provide locator processor output signals indicative of the location