Strangely enough, it’s illegal in Indiana and other locations to use a whistle when bicycling. Probably going back to olden times when police used whistles.
i have carried Halt for dogs in the past but only used it a couple of times. Very few dog problems in recent years. Amazing how many dogs out in Hoosier country land are contained by invisible fences. Can’t remember a single issue with Indianapolis urban/suburban dogs for a long time.