Various technologies pertaining to localizing multiple mobile computing devices in an indoor environment are described. Pairs of microphone arrays are selectively positioned in an indoor environment. A localization service assigns a frequency and schedule to a mobile telephone, and the mobile telephone begins outputting vibrations at the assigned frequency and in conformance with the assigned schedule. The microphone arrays sense the vibrations, and angles between the microphone arrays, respectively, and the mobile computing device are computed based upon the sensed vibrations. Such angles are subsequently employed to compute the location of the mobile computing device in the indoor environment.