If I may just add-on a little bit to clarify, I had to figure this out myself, and to save others confusion: *The vehicles folder you export to OpenFormats is connected to Vehicles.oac.* Place the 3 siren files into the folder "Vehicles", not into the folder in which the two files you exported (vehicles, vehicles.oac) are in. I'm sorry if it is overkill, just looking at the readme file made me scratch my head a few times. hope this helps.