A first lighting device comprises an electromagnetic sensor operable to receive an electromagnetic signal from at least one other lighting device, an acoustic sensor operable to receive an acoustic signal from the other lighting device, and a signal processing module. The signal processing module is configured to determine a distance between the first lighting device and the other lighting device by comparing the acoustic and electromagnetic signals received from the other lighting device. For example, the signals may be emitted when the other device detects occupancy in a space, and the first device may control its light output in dependence on receipt of the signals and the distance from the device that detected the occupancy.