Anechoic tile

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Sonar-reducing and sound-altering tiles

title: "Anechoic tile" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["stealth-technology", "submarine-components", "german-inventions-of-the-nazi-period"] description: "Sonar-reducing and sound-altering tiles" topic_path: "geography/germany" source: "https://en.wikipedia.org/wiki/Anechoic_tile" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Sonar-reducing and sound-altering tiles ::

NOTOC ::figure[src="https://upload.wikimedia.org/wikipedia/commons/8/82/HMS_Triumph_1_crop.jpg" caption="6}}. Two patches of missing tiles are visible towards the forward edge of the sail."] ::

Anechoic tiles are rubber or synthetic polymer tiles containing thousands of tiny voids, applied to the outer hulls of military ships and submarines, as well as anechoic chambers. Their function is twofold:

  • To absorb the sound waves of active sonar, reducing and distorting the return signal, thereby reducing its effective range.
  • To attenuate the sounds emitted from the vessel, typically its engines, to reduce the range at which it can be detected by passive sonar.

Development in the Third Reich

::figure[src="https://upload.wikimedia.org/wikipedia/commons/9/9c/UBOAT1308_5.png" caption="A close-up view of an ''Alberich'' tile, illustrating patterns of multiple holes with different diameters"] ::

The technology of anechoic tiles was developed by the Kriegsmarine during the Second World War, codenamed Alberich after the invisible guardian dwarf of the Rhinegold treasure from Richard Wagner's Der Ring des Nibelungen music dramas. The coating consisted of sheets approximately 1 m square and 4 mm thick, with rows of holes in two sizes, 4 mm and 2 mm in diameter.

Manufactured by IG Farben as a specially formed synthetic rubber tile and made using a stabilized, non-polar, high molecular weight polyisobutylene homopolymer with low-temperature elasticity; the rubber material itself was known by its trademark Oppanol.

The material was not homogeneous, but contained air cavities; these cavities resulted in a degraded reflection of ASDIC. The coating reduced echoes by 15% in the 10 to 18 kHz range. However, this degradation in echo reflection was not uniform at all diving depths due to the voids being compressed by the water pressure. An additional benefit of the coating was it acted as a sound damper, containing the U-boat's own engine noises.

::figure[src="https://upload.wikimedia.org/wikipedia/commons/8/88/Tarnung_U-480.jpg" caption="''Alberich'' tiles as they appear on U-480"] ::

The coating had its first sea trials in 1940, on , a Type IIB. Problems were encountered early-on, when it was found that the adhesive had insufficient strength to bond synthetic rubber with the pressure hull and casing. Furthermore, the coating was found to have considerably decreased the speed of the boat.

It was not until late 1944 that the problems with the adhesive were mostly resolved. The coating required a special adhesive and careful application; it took several thousand hours of glueing and riveting on the U-boat. The first U-boat to test the new adhesive was a Type VIIC.

Anechoic coating based on research & technology supplied by Germany was also used by the Japanese submarines, though completely different in composition from German rubber-based tiles like Alberich or Tarnmatte.

Modern day usage

After the war the technology was not used again until the late 1960s when the Soviet Union began coating its submarines, starting with the , in rubber tiles. These were initially prone to falling off, but as the technology matured it was apparent that the tiles were having a dramatic effect in reducing the submarines' acoustic signatures. Modern Russian tiles are about 100 mm thick, and apparently reduced the acoustic signature of s by between 10 and 20 decibels, (i.e. 10% to 1% of its original strength).

Modern tiles may consist of several layers of material with voids of variable sizes, designed to mask and deflect specific sound frequency ranges at different depths. Different materials may be used by marine engineers to cover sections of the submarine where they are needed to absorb specific frequencies associated with machinery at that location inside the hull.

The Royal Navy started using anechoic tiles in 1980, when was fitted with them during its second refit.

The United States Navy also started using anechoic tiles in 1980, with .

In recent years, nearly all modern military submarines are designed to use anechoic tiles.

References

Notes

References

  1. "Anti Sonar Coating". www.uboataces.com.
  2. "C.B. 04051 (76); U 135; Interrogation of Survivors; November, 1943". uboatarchive.net.
  3. "When the hunter becomes the prey – The first furtive submarine". Arte.
  4. "Oppanol – polyisobutenes". BASF – The Chemical Company.
  5. Rösler, Eberhard. ''Geschichte des deutschen U-Bootbaus, Band 2''. Bernard & Graefe Verlag. {{ISBN. 3-86047-153-8.
  6. "ASDIC Equipment Types – Section B". Jerry Proc.
  7. Eberhard Rossler. ''The U-Boat: The Evolution and Technical History of German Submarines''. Cassell. {{ISBN. 0-304-36120-8{{page?. (August 2019)
  8. 1-84176-872-3.
  9. "Report of interrogation of survivors of U 574, a 500-ton U-boat, sunk at about 0425 on 19th December, 1941, in position 38° 15' N. and 17° 16' W.". uboatarchive.net.
  10. McCartney, Innes.''Lost Patrols: Submarine Wrecks of the English Channel''. Periscope Publishing Ltd (2002). {{ISBN. 1-904381-04-9.{{page?. (August 2019)
  11. Rössler, Eberhard. ''Die Sonaranlagen der deutschen Unterseeboote: Entwicklung, Erprobung, Einsatz und Wirkung akustischer Ortungs- und Täuschungseinrichtungen der deutschen Unterseeboote''. Bernard & Graefe. {{ISBN. 3-7637-6272-8
  12. "Recubrimiento Anti-Sonar". u-historia.com.
  13. "revêtement en caoutchouc absorbant Alberich (tuile anéchoïque) pour sous-marin Uboote (stealth) marine allemande". loutan.net.
  14. "Подводные лодки. Проект 671, 671В, 671К".
  15. "Nuclear Submarine Refitting 1970–1983 (continued)".
  16. "Change of command welcome aboard pamphlet".

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