It's on the books in Ohio, but as someone else pointed out, use common sense. I've never heard of anyone being ticketed for not giving notice (even when they probably should have been).

When you're on a bici passing a pedestrian or another bici, DO give an audible signal. I'm not sure what the best thing to do is when it's a horse or horse-drawn buggy.... any of you horse people want to weigh in on that? Do I just pass?

DO honk when you're in your car passing a farm vehicle, a letter carrier's car, a slow ATV, etc., on a two-lane road without a marked passing zone.

When you're in a car passing a bici or pedestrian, if they're riding consistently or they've acknowledged your presence, just don't do it. If they seem oblivious to you, and it's someplace where you could pass an ordinary cyclist safely but they're not riding so that you can safely pass, just tap on your horn. There are different honks. Anyone can hear, appreciate and respond to the difference between tapping the horn 1/10 mile behind you to let you know you're there, vs. laying on the horn as they pass you.