Vehicle horn horn. Bicycles often have a classic "bulb horn", operated by squeezing a rubber bulb attached to a metal horn. Squeezing the bulb forces air through a steel reed located in the throat of the horn, making it vibrate, producing a single note. The flaring horn matches the acoustic impedance of the reed to the open air, radiating the sound waves efficiently, making the sound louder. Other types of horns used on bicycles include battery-operated horns (sometimes even car horns on 12-volt circuits are incorporated) and small air horns powered by a small can of compressed gas. Oliver Lucas of Birmingham,
Personal alarm Personal alarm A personal alarm is a small hand-held electronic device with the functionality to emit a loud siren-like alarming sound. It is activated either by a button, or a tag that, when pulled, sets the siren off. It is used to attract attention in order to scare off an assailant. The sound emitted can also have the effect of distracting, disorienting, or surprising the assailant. The volume varies from model to model, with some models having 130 decibels. Some personal alarms are also outfitted with an LED light for normal lighting purposes or to help deter an assailant. Due