yours?
maybe 25%
Probably more like 65 to 75% to the casual listener. Yes, if I wanted to emulate the sound of a particular bullhorn, then I might consider using an IR. But to go to all that trouble just for a "bullhorn" sound........
Actually I've been "into" IR's since the early eighties. After the first articles appeared in the AES journal it was introduced as "auralization" in the then cutting edge SysId software. Sonic Foundry picked it up later in the eighties with the Acoustic Modeler plugin, then Sek'D, etc. and finally 20 years later, Logic gets it. Works about the same as the old stuff did.