The ''Gruppenhorchgerät'' ('group listening device', abbreviated GHG) was a hydrophone array which was used on vessels of the German

Kriegsmarine The (, ) was the navy of Nazi Germany from 1935 to 1945. It superseded the Imperial German Navy of the German Empire (1871–1918) and the inter-war (1919–1935) of the Weimar Republic. The was one of three official military branch, branche ...

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

Development

In World War I carbon microphones 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, Radiochemistry, radiochemist, and a pioneer in crystallography, magnetism, piezoelectricity, and radioactivity. He shared the 1903 Nobel Prize in Physics with his wife, ...

in 1880. The quartz crystals generate electric voltage depending on the pressure acting on it. In collaboration with the Imperial German Navy, Atlas Werke AG 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 and barium titanate converters today.

U-Boat Group listening device

The GHG for

U-boats U-boats are naval submarines operated by Germany, including during the First and Second World Wars. The term is an anglicized form of the German word , a shortening of (), though the German term refers to any submarine. Austro-Hungarian Na ...

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 August 1941 was captured by the British

Royal Navy The Royal Navy (RN) is the naval warfare force of the United Kingdom. It is a component of His Majesty's Naval Service, and its officers hold their commissions from the King of the United Kingdom, King. Although warships were used by Kingdom ...

. Only in May 1942 the submarine’s ELAC equipment was thoroughly analyzed; the above resolution values were determined.

''Balkongerät''

The GHG could not be used whilst cruising on the surface, and it could not effectively at periscope depth. The optimum operating modus was at a depth below 20 meter with a reduced speed of less than 3 knots. To solve this, a new listening device, known as ''Balkongerät'' ('balcony-device') was developed. It was mounted at the front and the bottom of a submarine, so it had less interference from surface noise. There was however now a dead zone towards the rear of the submarine. The Balkongerät was successfully tested on in January 1943. It was installed on some small

Type VII submarine Type VII U-boats were the most common type of Nazi Germany, German World War II U-boat. 704 boats were built by the end of the war. The type had several modifications. The Type VII was the most numerous U-boat type to be involved in the Battle of ...

and was standard on the new large Type XXI submarineA O Bauer (2005) Some hardly known aspects of the GHG, the U-boat's group listening apparatus
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Surface ship Group listening device

German Capital ships were equipped with the GHG typ 57 manufactured by Atlas, Bremen. It consisted of 60 crystal microphones and had a typical range of between four and six kilometers, although in most favourable circumstances a range of 40 kilometers was possible.

Citations

References

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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