A speaking tube, also known as a megaphone or voicepipe is a simple, short range mechanical sound transmission device, consisting of a metal tube or pipe stretching from one fixed location to another, often with horn shaped apertures at either end. These tubes were most often used in older buildings and on board ships but gradually fell out of common use with the advent of more sophisticated communication systems such as telephone, radio, and intercoms. In 2011, they can sometimes still be found at sites that have been preserved for their historical significance, old buildings, some older ships, and even in playgrounds as amusement for children.
On board ships, a speaking tube is more likely to be called a voicepipe, in line with the long maritime tradition of unique nomenclature for many items and practices. On land, a device of this type is called a speaking tube or sometimes a megaphone. Their history goes back several centuries to at least the 17th century and perhaps even earlier. They were most common on ships, particularly warships, although it was not uncommon for them to be found on large commercial ships as well, especially as ships became larger in the 19th and early 20th centuries. On land, they were often found in large buildings, in the homes of affluent private citizens, and occasionally, in automobiles, trains, or airplanes.
A typical speaking tube consists of a long length of pipe, nearly always metal, that stretches from one location to another in a place where quick communication is desired. The pipe, typically ranging in diameter from 1 to 4 inches (2.5 to 10 cm) might be very long, sometimes hundreds of feet (1 foot = 0.3 meters), and could have many bends. Bends are made with smooth arcs in the metal rather than angular corners, as angular corners reduce sound transmission efficiency. A horn or funnel-shaped attachment is mounted at either end, giving rise to the saying, "Get on the horn," that is still used today. A speaking tube is capable of transmitting conversational speech through simple sound amplification by the focused channeling of sound through the horns and the tube, making it seem to the listener if the speaker were right beside them.
Where these devices were, and sometimes still are, used it is common to find more than one tube aperture so that one person can communicate with several other areas on board a ship or in a building. On board an older ship for example, there may be several voicepipes on the bridge leading to various areas such as the engine room, the captain's quarters, or the gunnery stations, in the case of a warship. In some cases, after the advent of more advanced communication systems, speaking tubes and voicepipes were used as back-up systems.
On very long speaking tubes, the ends were often fitted with removable whistles to allow a person at one end to signal to the other end that communication was desired. On board ships and other vehicles, the tubes were often insulated with cloth batting to reduce noise interference. Covers for the horns prevented the entrance of water when used on an open deck. Some later voicepipes, particularly on warships, were even fitted with emergency valves so they could be sealed to prevent water leakage from one compartment to another in case of a hull breach.