If I had been sounding a fog signal I wouldn't have been able to hear some of the boats around me. There were several small boats that only showed up intermittently on radar that I knew for sure were there only by sound. One example was a 14' wooden skiff that I heard long before it showed up on my radar or I saw it. I do sound my horn if I am in a defined channel, but that doesn't happen much. I do regularly hear fog horns on the Bass Harbor Bar, but since I hear those from my house, I generally don't worry about the boats.