A method and system for detecting structural damage in a structure by detecting acoustic emissions from damage in a structure to obtain acoustic emission data, and processing the acoustic emission data in accordance with a model characterising acoustic paths. The model is built by inducing a plurality of types of acoustic emissions at each of a plurality of positions on a structure, the plurality of types of acoustic emissions corresponding to a respective plurality of types of structural damage. The acoustic emissions are detected using at least three sensors arranged on the structure, and the detected acoustic emissions are processed for each position to determine model data characterising effects on each type of acoustic emission from each position of acoustic paths between the positions and the sensors. The processed data is then stored as model data.