science

Gruppenhorchgerät

Gruppenhorchgerät is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Gruppenhorchgerät rather than just read about it. In short: The Gruppenhorchgerät ('group listening device', abbreviated GHG) was a hydrophone array which was used on vessels of the German Kriegsmarine in World War II. Development In World War I carbon microphones were still used as sound receivers.

Key takeaways

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Reproduce the core statement of Gruppenhorchgerät from memory before moving on to harder problems.

Reference excerpt

The Gruppenhorchgerät ('group listening device', abbreviated GHG) was a hydrophone array which was used on vessels of the German Kriegsmarine in World War II.

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 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 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 high-pass filters with 1, 3 and 6 kHz cutoff frequency (and a bypass without filtering). A disadvantage of the side mounting was a dead zone of 40 ° to fore and aft. Each hydrophone had its own tube amplifier, with input either direct or through a coupling transformer. The amplifier outputs were switchable on/off, and connected to wipers on a wheel, with positions mirroring the positions of the hydrophones on the hull. The wipers then were in contact with an array of parallel strips, connected to a portion of an electrical analog delay line, a linear array of capacitors and inductors. The angle of the wheel selected the delays applied to each hydrophone signal, superimposing them with the delays from speed of sound in water. The operator then switched on/off the relevant hydrophones, rotated wheel until the interferences maximized (the signal of the target was loudest). The position on the goniometer coupled to the wheel then shown the azimuth towards the target. The output of the delay line was connected to a tube preamplifier, fed into a filter stage. The selectable filters allowed listening to different frequencies (low for longer distance, high for precision aiming). The output was then further amplified for a set of headphones or a speaker. The assembly acted effectively as electronically steered phased array.

Range: 20 km to individual ships, 100 km against Convoy Search area: 2 × 140 ° Resolution: <1 ° at 6 kHz 1.5 ° for 3 kHz 4 ° for 1 kHz 8 ° without filter In August 1941 U 570 was captured by the British Royal Navy. 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 while cruising on the surface, nor 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 U-194 in January 1943. It was installed on some small Type VII submarines and was standard on the new large Type XXI submarine

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 Draminski, Stefan (2018). The battleship Bismarck. Osprey Publishing. ISBN 978-1472828880. Schmalenbach, Paul (2001). Kreuzer Prinz Eugen unter drei Flaggen [Cruiser Prinz Eugen under three flags] (in German). Hamburg: Koehler. ISBN 3-7822-0823-4.

See also Die Sonaranlagen der deutschen U-Boote, Entwicklung, Erprobung, Einsatz und Wirkung akustischer Ortungs- und Täuschungseinrichtungen der deutschen Unterseeboote. Bernard & Graefe, September 2006, ISBN 3-7637-6272-8 Eberhard Rössler: Die deutschen U-Boote und ihre Werften. Bernard & Graefe, 1990, ISBN 3-7637-5879-8 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, ISBN 0-1129-0423-8 Holt, L. E. (1947). "The German Use of Sonic Listening in World War II". The Journal of the Acoustical Society of America. 19 (4). Acoustical Society of America (ASA): 725. Bibcode:1947ASAJ...19R.725H. doi:10.1121/1.1916561. ISSN 0001-4966. Eberhard Rössler: Die Sonaranlagen der deutschen Unterseeboote. Koehler, Herford, 1991, 2. Auflage, ISBN 3-7637-6272-8 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

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Worked examples

Example 1 — a first encounter with Gruppenhorchgerät

Start with the simplest possible case. Write down what Gruppenhorchgerät claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Gruppenhorchgerät before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Gruppenhorchgerät ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Gruppenhorchgerät

In research: Gruppenhorchgerät appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Gruppenhorchgerät in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Gruppenhorchgerät is common in secondary-school and first-year university syllabi. It links to neighbouring topics German inventions of the Nazi period, Microphones, Sonar, so understanding it makes those chapters shorter.
In everyday life: Look for Gruppenhorchgerät outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Gruppenhorchgerät in 20 minutes

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Close the page and write down what Gruppenhorchgerät means in your own words.
Compare your version with the excerpt and mark what you missed.
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Frequently asked questions

What is Gruppenhorchgerät in simple terms?

The Gruppenhorchgerät ('group listening device', abbreviated GHG) was a hydrophone array which was used on vessels of the German Kriegsmarine in World War II. Development In World War I carbon microphones were still used as sound receivers.

Why does Gruppenhorchgerät matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Gruppenhorchgerät?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Gruppenhorchgerät.