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,
Muster drill trips on the water, such as those taken on ferries, dinner cruises, and riverboats. On ferries, a safety briefing delivered through the PA system alerts passengers to the sound pattern of the emergency alarm and what to do if the signal is heard. Generally, the muster drill is taken in simple instructions: The "general emergency alarm" consists of seven or more short blasts followed by one long blast of the ship's horn or whistle (some lines don't sound the signal on the horn or whistle) and by the ship's internal alarm (such as fire alarm bells accompanied with flashing strobe