The horn was meant to indicate 15 minutes quiet time. Same as the drum show which I attended in November too. Shame NO-ONE acknowledged it. I think there should be some kind of sound limiter set up in the exhibition hall to make sure it only gets to a certain level...
All the noise inside made the hall me appreciate the Overwater stand just outside of all the noise, however. I'm now saving up to buy one of their models as soon as it comes out in a few months!! Beautiful, beautiful basses.