Having been to many shows and setting up systems when I was a dealer ,to be fair to all ,they should all have to bring a spl meter and all rooms should be max under 88db.which is fairly loud For several reasons. In smaller rooms too many hard reflections ,and hard sounds because of this, also to not impede on other systems in other rooms , also it’s a known fact that 90 db + spl level creates hearing loss over accumulated time.
vendors should be at the end of hallway so all the disturbing chatting won’t disturb musical demo’s. That’s just from my experiences . For Everyone pays monies to present their products , and people go to listen . Common courtesy goes a long way !!