The word "horn" refers to a hard pointed or bony growth on the head of certain animals, such as cows or rhinoceroses. It can also mean a sound-producing device, usually made of brass, that can be blown into to make noise. Full definition
I've heard some suggest carrying an air horn of sorts or whistle that can be blown loudly. (montrealdogblog.com)
We sat in awe as fifteen big horn sheep showed themselves during the trip. (incadventures.com)
On the first day, I took my seat at the table assigned to our creative department, next to a nice woman who I suspect was an air horn in a former life. (slaw.ca)