The ''Gruppenhorchgerät'' ('group listening device', abbreviated GHG) was a

hydrophone A hydrophone ( grc, ὕδωρ + φωνή, , water + sound) is a microphone designed to be used underwater for recording or listening to underwater sound. Most hydrophones are based on a piezoelectric transducer that generates an electric potenti ...

array An array is a systematic arrangement of similar objects, usually in rows and columns. Things called an array include: {{TOC right Music * In twelve-tone and serial composition, the presentation of simultaneous twelve-tone sets such that the ...

which was used on

Nazi Germany Nazi Germany (lit. "National Socialist State"), ' (lit. "Nazi State") for short; also ' (lit. "National Socialist Germany") (officially known as the German Reich from 1933 until 1943, and the Greater German Reich from 1943 to 1945) was ...

U-boat U-boats were naval submarines operated by Germany, particularly in the First and Second World Wars. Although at times they were efficient fleet weapons against enemy naval warships, they were most effectively used in an economic warfare ro ...

s in

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...

Development

In World War I

carbon microphone The carbon microphone, also known as carbon button microphone, button microphone, or carbon transmitter, is a type of microphone, a transducer that converts sound to an electrical audio signal. It consists of two metal plates separated by gra ...

s were still used as sound receivers. The individual receivers were mostly placed in the front part of the vessel along the hull sides to have enough distance from the screw and the noise they emitted. The individual microphones were arranged in groups and each was oriented in a different direction. The individual microphones had to be connected manually to take bearings. They were not very reliable, so other transducers were experimented with. Dynamic microphones were also discarded. At the end of the process, the piezoelectric principle was deemed the most suitable. This was discovered by

Pierre Curie Pierre Curie ( , ; 15 May 1859 – 19 April 1906) was a French physicist, a pioneer in crystallography, magnetism, piezoelectricity, and radioactivity. In 1903, he received the Nobel Prize in Physics with his wife, Marie Curie, and Henri Becq ...

in 1880. The quartz crystals generate electric voltage depending on the pressure acting on it. In collaboration with the

Imperial German Navy The Imperial German Navy or the Imperial Navy () was the navy of the German Empire, which existed between 1871 and 1919. It grew out of the small Prussian Navy (from 1867 the North German Federal Navy), which was mainly for coast defence. Wilhel ...

Atlas Werke AG Atlas Werke was a German shipbuilding company, located in Bremen. It was founded in 1911. During World War I Atlas Werke built one single U 151 U-boat for the Kaiserliche Marine, the . After the war, Atlas Werke also started to make echo soun ...

in Bremen and ''Electroacustik'' (ELAC) in Kiel worked on piezoelectric transducers and the development of detectors and amplifiers in general. They experimented with different kinds of crystals, or combinations of several of them. The best result rendered the Seignette crystal, which is formed from a mixture of different salts. From 1935 crystal receivers were permanently installed on all German submarines. Modern submarines still use

electrostriction Electrostriction (cf. magnetostriction) is a property of all electrical non-conductors, or dielectrics, that causes them to change their shape under the application of an electric field. Explanation Electrostriction is a property of all dielectri ...

and barium titanate converters today.

Group listening device

The group listening device (‘’Gruppenhorchgerät’’), abbreviated "GHG", consisted of two groups of 24 sensors (one group on each side of the ship). Each sensor had a tube preamplifier. These 48 low frequency signals were then routed to a switching matrix in the main unit. The sonar operator could determine the ship's side and the exact direction of the sound source. To improve the resolution, there were three switchable crossover with 1, 3 and 6 kHz center frequency. A disadvantage of the side mounting, was a dead zone of 40 ° to fore and aft. Range: 20 km to individual drivers, 100 km against Convoy Search area: 2 × 140 ° Resolution: <1 ° at 6 kHz, 1.5 ° for 3 kHz, 4 ° for 1 kHz; without crossover 8 ° In May 1942 was captured by the British

Royal Navy The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against Fr ...

. The submarine’s ELAC equipment was thoroughly analyzed; the above resolution values were determined.

''Balkon''

The GHG fitted to early U-boats could not be used effectively at periscope depth. To solve this, a new listening device, known as ''Balkon'' ('balcony'), fitted to a second, lower hull, was successfully tested on in January 1943.A O Bauer (2005) Some hardly known aspects of the GHG, the U-boat's group listening apparatus
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References

* ''Die Sonaranlagen der deutschen U-Boote'', Entwicklung, Erprobung, Einsatz und Wirkung akustischer Ortungs- und Täuschungseinrichtungen der deutschen Unterseeboote. Bernard & Graefe, September 2006, * Eberhard Rössler: ''Die deutschen U-Boote und ihre Werften''. Bernard & Graefe, 1990, * Heinrich Stenzel: ''Leitfaden zur Berechnung von Schallvorgängen''. Holt, 1947 Seiten 678–679 * Willem Hackmann: ''Seek & Strike Sonar, anti-submarine warfare and the Royal Navy 1914–54''. Science Museum, London 1984, * * Eberhard Rössler: ''Die Sonaranlagen der deutschen Unterseeboote''. Koehler, Herford, 1991, 2. Auflage, * ''Beschreibung einer K.D.B.-Anlage für Oberflächenschiffe'', Atlas-Werke Aktiengesellschaft (Herausg.), Nr. 472, (K.D.B. = Kristall-Dreh-Basis = Empfängerbasis), Bremen, 1938, Halbleineneinband, Großformat, 49 Seiten, 81 Falttafeln, Anlagen, GEHEIM, * ''Verfahren zur Richtungsbestimmung von Schallsignalen'', Reichspatentamt, Nr. 320/29 im August 1918 * Über Hörempfindungen im Ultraschallgebiet bei Knochenleitung, Atlas-Werke AG., Bremen 1940

External links

Vortrag Chef N Wa I am 10. März 1944 vor der Arbeitsgemeinschaft „Ortungsgeräte“
(PDF; 1,3 MB)
Erzeugung von Ultraschall mit Ferriten, Ulrich Enz, Zürich 1955

Paul Profos,Tilo Pfeifer: ''Handbuch der industriellen Messtechnik''.
Oldenbourg, 1994,

German Hydrophones

Development of Underwater Sound and Detection Equipment

* ''Evaluation of German Sonic Listening Equipment „GHG“ on the USS Witek’’ {{DEFAULTSORT:Gruppenhorchgerat Microphones U-boats World War II German electronics Sonar German inventions of the Nazi period