Conventional electrical techniques for the monitoring of partial discharge (p.d.) activity in enclosed systems like gas insulated substations (GIS) have certain inherent limitations, which has prompted the exploration of non-electrical techniques. Acoustic detection of p.d. in a GIS is based on the retrieval and analysis of mechanical signals produced on the walls of the metallic enclosure due to electrical discharge activity within. A theoretical modelling of the process by which a discharge produced within the GIS sets up detectable signals on the walls of the enclosure seems to be lacking. The present work consists of the development of a model for the propagation of electrically induced acoustic waves through gaseous medium, and their effect on the walls of the GIS, giving adequate representation to fluid–structure coupling. A numerical simulation of the process is shown to yield important information about the proper type of instrumentation required for such non-invasive tests, and aid in designing robust strategies for locating the source of the discharge.