Abstract: An acoustic model determination approach for a real-time locating system is disclosed. The system includes one or more transmitting devices and one or more mobile devices. The acoustic model may be determined by deriving an acoustic representation of sub-structures within the building, and then forming the acoustic model based on the acoustic representation and the location and orientation of the static acoustic transmitting device. In another embodiment, an acoustic signal is transmitted from a static acoustic transmitting device, with the reflected signals received by the same static acoustic transmitting device in a receiving mode. Based on these received acoustic signals, the acoustic model is formed based on the reflected signals and the location and orientation of the static acoustic transmitting device.