Anechoic tile Anechoic tiles are rubber or synthetic polymer tiles containing thousands of tiny voids , applied to the outer hulls of military ships and submarine s , as well as anechoic chamber s . Their function is twofold : 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 . It was manufactured by IG Farben from a material known under its trade name of " Panadol " ( basically PIB , see also synthetic rubber ) . The material was not homogeneous but contained air cavities ; it was these cavities that degraded the reflection of ASDIC . 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 . 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 . U - 67 , a Type IX , was the first operational U - boat with this coating . After her first war patrol , she put in at Wilhelmshaven probably sometime in April 1941 where she was given the coating , it 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 . 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 U - 480 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 , " U - 4709 " , was coated with the anechoic tiles . U - boats with the anechoic tiles coating include : , U - 480 , U - 485 U - 486 , U - 1105 , U - 1106 , U - 1107 , U - 1304 , U - 1306 , U - 1308 , U - 4704 , U - 4708 and U - 4709 . The Japanese I - 400 super - submarine also used anechoic tile technology supplied by Germany . Use by the Soviet Union . After the war the technology was not utilized again until the 1970s when the Soviet Union began coating its submarines 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 signature s . 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 usage . The modern materials consist of a number of layers and many different sized voids , each targeted at a specific sound frequency range at different depths . Different materials are sometimes used in different areas of the submarine to better 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 her second refit . The US Navy started using anechoic tiles in the mid - 1980s , with the improved 688 - class submarine USS " San Juan " being the first boat to receive them . Nearly all modern submarines are now designed with them .