Our group included chemical-propellant, air- ûpropellant and lung-powered horns (and whistles). ûSeveral horns claim to be louder than our tests ûindicated. Two samples of one model malfunc- tioned during testing.

Most boats don’t come fully equipped from the manufacturer, or even from a dealer. One critical item that may be absent—especially on smaller boats—is a “sound-signaling appliance.” Referred to in the US Coast Guard navigation rules only as “whistles,” it could be a horn, a whistle, a siren, or any mechanical sound-producing tool.

A sound-signaling appliance is required on all vessels no matter the size. (Larger vessels—those over 39' 4"—must meet more exact requirements.) Handheld portable horns—whether air-, propellant-, or lung-powered—may be used to fulfill this mandate, and some standard whistles may even fill the bill. What’s the bill? Coast Guard rules state that every boat must carry a device…