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ca 1914 __ The Gamage Ltd Sound Locator No1 Mk1 — Acoustic location
Comment : Acoustic location is the art and science of using sound to determine the distance and direction of something. Location can be done actively or passively, and can take place in gases (such as the atmosphere), liquids (such as water), and in solids (such as in the earth). Sound is a disturbance of mechanical energy that propagates through matter as a longitudinal wave, and therefore is a mechanical wave. ... 1) Active acoustic location involves the creation of sound in order to produce an echo, which is then analysed to determine the location of the object in question. 2) Passive acoustic location involves the detection of sound or vibration created by the object being detected, which is then analysed to determine the location of the object in question. Both of these techniques, when used in water, are known as sonar; passive sonar and active sonar are both widely used. The F70 type frigates (here, La Motte-Picquet) are fitted with VDS (Variable Depth Sonar) type DUBV43 or DUBV43C towed sonars SONAR (SOund Navigation And Ranging) ” or sonar ” is a technique that uses sound propagation under water (primarily) to navigate, communicate or to detect other vessels. ... Acoustic mirrors and dishes, when using microphones, are a means of passive acoustic localisation, but when using speakers are a means of active localisation. Typically, more than one device is used, and the location is then triangulated between the several devices. Acoustic location in air was used from mid-WWI to the early years of WWII for the passive detection of aircraft by picking up the noise of the engines. It was rendered obsolete before and during WWII by the introduction of radar, which was far more effective but interceptable. Acoustics has the advantage that it can see round corners and over hills. The general principle of a horn type locator is similar to common 19th century listening enhancement devices, such as ear horns, but scaled up in size. One moderately well known example has become infamous as the Japanese War Tuba, due to the apparent resemblance to the western musical instrument. A horn is a tapered sound-guide designed to provide an acoustic impedance match between a sound-producing device and the characteristic impedance of free space. ... Of course, the best-known form of this type of locator is the human ear. Bat ears come in different sizes and shapes The ear is the sense organ that detects sound. ... (For example : 4.5 metre high WW1 concrete acoustic mirror near Kilnsea Grange, Yorkshire, UK. The pipe which held the 'collector head' (microphone) can be seen in front of the structure; A large concrete mirror is used to focus sound on a microphone. Clever design allows for the ability to not only determine range but direction as well. Image File history File linksMetadata No higher resolution available. ... Image File history File linksMetadata No higher resolution available. ... An acoustic mirror is a device used to focus and amplify sound waves.) A few acoustic mirrors still can still be found on the coast of Britain to this day. Such devices are said to have been able to detect aircraft as far away as 20 miles, or more. An acoustic mirror is a device used to focus and amplify sound waves. ...This model was used for location in the First World War, when aircraft flew relatively slowly and acoustic detection was a fairly practical proposition. It was manufactured by A.W. Gamage Ltd, who ran a famous department store in London specialising in toys, bicycles etc.The Mk 1 Sound Locator was manufactured by A.W. Gamage Ltd. in Britain during the first World War. In the early days of the First World War, anti-aircraft defence was a totally new field. The detection of unseen incoming aircraft was a major problem. The only possible solution with the technology available at the time was sound detectors, which could provide a rough idea of an aircraft's direction and height based upon the sound of its engine. Tubes connected the bases of two horizontally mounted gramophone-style horns to a pair of stethoscope earpieces. An operator moved the detector until the sound was heard equally in each ear, at which point (theoretically) it would be pointed in the direction of the aircraft. A second operator used the vertically mounted horns to estimate height. The system was rudimentary at best, however, as the location of the aircraft could only be established for the time that the sound was recorded. After a sound contact was made, laborious calculations were then required to properly aim an anti-aircraft gun, and any deviation in the aircraft's flight path rendered the system useless. It was, however, the only system available for detecting the approach of unseen aircraft until the development of radar in the 1930s. (Compiled from various sources)Other next inventions : A two-horn system at Bolling Field, USA, in 1921; A Czech four-horn acoustic locator in the 1920s (There are two horns in the horizontal plane, and two staggered in the vertical plane. Scoop-shaped reflectors direct the sound into large-diameter tubes. Manufactured by Goerz.); The height-locating half of the Czech four-horn acoustic locator; A four-horn acoustic locator in England in 1938 (There are two horns in the horizontal plane, and two in the vertical plane. The latter are at top and bottom left of the picture. Whether the horns were of crude flat wood construction as they appear to be, or if the flat panels were a protective casing for a more conventional horn remains a matter for speculation at present. (in Popular Mechanics for Dec 1938); A four-horn acoustic locator again, in England in the 1930s (Once more there are three operators, two with stethoscopes linked to pairs of horns for stereo listening. The exact method of operation is currently unknown, but I suspect was as follows: the man on the left adjusts the mounting elevation until the aircraft noise is apparently central, while the chap on the right adjusts the bearing for the same result. The man in the middle reads bearing and elevation from dials and transmits it by telephone to the air defence system where the results from several locators can be combined to triangulate the target, and give its approximate height and position. (in a book called “Aerial Wonders of Our Time” published in Dec 193?); Acoustic locator on trial in France in the 1930s (This remarkable machine is an acoustic locator based on hexagons. Each of the four assemblies carries 36 small hexagonal horns, arranged in six groups of six. Presumably this arrangement was intended to increase the gain or directionality of the instrument.); A German RRH acoustic locator in the 1940s (This apparatus was called the Ringtrichterrichtungshoerer (or RRH) which Matthias Warkus tells me translates literally as "ring funnel direction hearer", or more accurately: "ring-horn acoustic direction detector". The RRH was mainly used in World War 2 antiaircraft searchlight batteries for initial aiming of the searchlights at night targets, presumably because it was cheaper and easier to make than a radar set. Later in the war they were replaced by radar sets. Like the British and French versions, the RRH was also composed of four horns, two to determine bearing, and two for elevation, arranged in a ring. The two lateral horns have a horizontal bar across their mouths. The RRH could detect targets at distances from 5 to 12 km, depending on weather conditions, operator skill, and the size of the target formation. It gave a directional accuracy of about 2 degrees. It had a crew of three - traverse aimer on the left seat, elevation aimer on the right seat and a dial-reader/talker in the middle. The rolled-up material above the operators' heads could be unfurled to provide shelter.); A US Army sound locator in the early 1940s (The locator and control station were connected by cables to the searchlight and a mobile electricity generator. Note there are three horns and not four, the one in the middle here being shared between the horizontal and vertical planes. These locators continued to be deployed when radar sets were introduced, in the hope of convincing the Germans that the US searchlight battalions were still dependant on acoustic location.).The first Japanese attack on the fortress island of Corregidor (in the Phillipines) on 29th December 1941 was detected by American acoustic locators. (Compiled from various sources)The Japanese war tuba is a colloquial name sometimes applied to Imperial Japanese Army acoustic locators due to the visual resemblance to the musical tuba. The name derived from a misidentification, possibly in jest, of a historical photo from the 1930s featuring the Japanese emperor Shôwa inspecting the acoustic locators with anti-aircraft guns in the background. Acoustic location was used from mid-World War I to the early years of World War II for the passive detection of aircraft by picking up the noise of the engines. It was rendered obsolete before and during World War II by the introduction of radar, which was far more effective. Some examples of concrete, acoustic location mirrors can still be found on the seacoast of Britain to this day. (Compiled from various sources).Before the invention of radar, the direction finding abilities of human ears were used to act as an early warning system for detecting planes. They used large horns which were attached with tubes into an operator's ears. The operator then moved the horns until they sounded like they were pointing at the aircraft, and because they were so far apart the direction was much more accurate than ears alone. (Dave Ansell)“Japan is spending $26,000,000 for modernizing and expanding its armaments. Here are some of the huge “ears” intented to detect the presence of enemy aircraft.”. (From the US magazine Mechanics & Handicraft, Jan 1936)
Urls : http://www.museumwaalsdorp.nl/en/Mk1soundlocator.html (last visited ) http://www.warmuseum.ca/ (last visited ) http://freespace.virgin.net/richard.wordsmith/roc/rochist.htm (last visited ) http://www.dself.dsl.pipex.com/MUSEUM/COMMS/ear/ear.htm (last visited )

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