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__NOTOC__ 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 by Nazi Germany== The technology of anechoic tiles was developed by the Kriegsmarine in the Second World War, codenamed ''Alberich'' after the invisible dwarf from Germanic Mythology. The coating was made up of sheets approximately square and thick, with rows of holes in two sizes, and in diameter.〔(【引用サイトリンク】title=Anti Sonar Coating )〕〔(【引用サイトリンク】title=C.B. 04051 (76); U 135;Interrogation of Survivors; November, 1943 )〕〔(【引用サイトリンク】title=When the hunter becomes the prey - The first furtive submarine )〕 It was manufactured by IG Farben from a material known under its trade name of "Oppanol" (basically PIB, see also synthetic rubber).〔〔〔(【引用サイトリンク】title=Oppanol® - polyisobutenes - BASF - The Chemical Company - Corporate Website )〕 The material was not homogeneous but contained air cavities; it was these cavities that degraded the reflection of ASDIC.〔Rösler, Eberhard. ''Geschichte des deutschen U-Bootbaus, Band 2''. Bernard & Graefe Verlag. ISBN 3-86047-153-8.〕 The coating reduced echoes by 15% in the 10 to 18 kHz range.〔 This frequency range matched the operating range of the early ASDIC active sonar used by the Allies. The ASDIC types 123, 123A, 144 and 145 all operated in the 14 to 22 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.〔Eberhard Rossler. ''The U-Boat: The Evolution and Technical History of German Submarines''. Cassell. ISBN 0-304-36120-8〕 An additional benefit of the coating was it acted as a sound dampener, containing the U-boat’s own engine noises.〔 The coating had its first sea trials in 1940, on , a Type IIB.〔〔 , a Type IX, was the first operational U-boat with this coating.〔 After its first war patrol, it put in at Wilhelmshaven probably sometime in April 1941 where it was given the coating. The coating covered the conning tower and sides of the U-boat, but not to the deck. By 15 May 1941, ''U-67'' was in Kiel performing tests in the Baltic Sea. During July, the coating was removed from all parts of the boat except the conning tower and bow. Further experiments and sound trials were made in the Little Belt but they presumably proved unsatisfactory, as all the coating was subsequently removed. Problems were encountered early-on, when the adhesive was found to be not strong enough to stick the synthetic rubber sheets to the pressure hull and casing of the U-boat.〔〔 This resulted in the sheets loosening and creating turbulence in the water, making it easier for the submarine to be detected.〔Williamson, Gordon. ''Wolf Pack: The Story of the U-Boat in World War II''. Osprey Publishing; First Edition (February 5, 2005). ISBN 1-84176-872-3.〕 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.〔McCartney, Innes.''Lost Patrols: Submarine Wrecks of the English Channel''. Periscope Publishing Ltd (28 Dec 2002). ISBN 1-904381-04-9.〕 The first U-boat to test the new adhesive was a Type VIIC.〔〔 With good results with the new adhesive, the Oberkommando der Marine intended that it would be widely used on the new Type XXI and Type XXII U-boats. However, the war ended before it could be put into large scale use.〔 Ultimately only one operational Type XXIII, , was coated with the anechoic tiles.〔 U-boats with the anechoic tiles coating include: , , , , , , , , , , and .〔Wynn, Kenneth G. ''U-Boat Operations of the Second World War: Career Histories, U1-U510''. Naval Institute Press (March 1998). ISBN 1-55750-860-7.〕〔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〕〔(【引用サイトリンク】title=Recubrimiento Anti-Sonar )〕 The Japanese I-400 super-submarine also used anechoic tile technology supplied by Germany. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「anechoic tile」の詳細全文を読む スポンサード リンク
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