What do 3 short blasts on a horn or whistle indivate?

Three short blasts on a horn or whistle typically indicate a specific signal or warning. In maritime contexts, it can mean "man overboard" or that a vessel is about to maneuver. In other situations, such as in safety drills or sports, it may signal the start or end of an event or a call for attention. The exact meaning can vary by context, so it's essential to be aware of the specific protocols in use.