Speaking tube

A speaking tube or voicepipe is a device based around two cones connected by an air pipe through which speech can be transmitted over an extended distance. While its most common use was in intra-ship communications, the principle was also used in fine homes and offices of the 19th century, as well as fine automobiles, military aircraft, and even locomotives. For most purposes, the device was outmoded by the telephone and its widespread adoption. This device was also known as a "megaphone", but that use has since become superseded.

Design

Early voicepipes consisted of two cones, of wood or metal, one end shaped to fit the speaker's mouth, connected to the other which was flared so as to amplify the sound.

Later designs of the voicepipe inserted a removable cork-mounted whistle, which could be sounded by blowing into the tube from the other end. On naval vessels, this created a distinctive sound associated with urgent intra-ship communication on old warships. The sound of the whistle would summon the listener, who would remove the whistle and answer the call.

Voicepipes had no switching mechanism, and so to provide multiple destinations, multiple voicepipes with dedicated transit pipes would have to be provided between all desired endpoints.

The technology continued to be used into the electronic age, due to their reliability and low cost, though sometimes combined with electronic signaling. Warships built as late as the 1950s continued to incorporate voicepipes alongside more advanced technology, perhaps as a fail-safe in the event of power failure or EMP.

Maritime use

Voice pipes, the maritime term, served to transmit reports from lookout positions aloft to the deck and from the bridge to the steering position and engine room. These are somewhat larger in diameter than the domestic version and are ofter lagged in sound absorbent material to increase their efficiency. About 1780, one captain removed a canvass voice pipe installed by an imaginative midshipman saying he was sure the topmen would “use it for an improper purpose”Pseudo. 'Suffolk Coast' (1933). "Memories of an Old Ipswich Mariner" Capt. R. H. Gower. Suffolk Chronicle 2nd December.] .

One disadvantage of voice pipes is that they may breach the integrity of watertight spaces. This led to the introduction of shut-off valves for the voicepipes on either end, to prevent floodwater in one compartment from entering other compartments via its voicepipes.

Permanently fitted, rigid voice pipes are still in use and are generally covered with heavy lids to avoid ingress of water. The speaker has to place the mouth over the bell-shaped end of the pipe and the receiver has to 'bend an ear' to hear what is being said.

Domestic use

In domestic applications, the voicepipe was of smaller design and referred to as "speaking tubes". The ends of the tube were often flexible for convenience of use. The speaking tube supplemented the array of remotely controlled hand bells that were operated in the upstairs rooms and rang in the servant's quarters in even modest houses in the 19th century. The phrase "give him a blow" and the use of "blower" as a synonym for "telephone" are generally accepted as having their origin in this feature of speaking tubes.

In some offices, speaking tubes were employed within the office, with whistles at either end. Multiple speaking tubes could be hung from the edge of a desk, to make or receive calls to and from multiple associates.

Speaking tubes were also used in fine automobiles, allowing communication with the driver from the passenger's compartment.

Playgrounds

Today, the principle of the speaking tube can be found on certain playground equipment, which employ tubing connecting soundhorns or other speaking boxes to allow voices to travel to separate points, for the amusement of the children. [http://www.gametime.com/pdetail.asp?l=Components&g=Discovery%20Series&pn=Sound%20Tube&mn=7037&promo=0]

A similar device, often used by children at play, is the tin can telephone, which consists of two tin cans open at one end connected by string tied into the closed end of each can. When the cans are pulled apart so that the string is held tight, even a softly spoken voice can be heard clearly over a considerable distance.

References

* The Amplifier Institute:
** [http://www.dself.dsl.pipex.com/MUSEUM/COMMS/voicepipe/voicepipe.htm#voice Maritime voice pipes and terrestrial speaking tubes]
** [http://www.dself.dsl.pipex.com/MUSEUM/LOCOLOCO/quadruplex/quadrapl.htm Voicepipe usage proposed for a locomotive (never built).]