Anechoic coatings are exterior treatments to a submarines hull designed to reduce the ships acoustic signature. The coatings can be engineered to attenuate sonar returns and/or mask internal vibrations from machinery or equipment.
Coatings are typically made of viscoelastic materials, such as rubber or urethane polymers.
Coatings have generally been of tile-based construction, though spray-on coatings are now available.
Alberich tiles were a world war two German development, 4mm thick tiles of rubber designed to attenuate within the frequency range of allied ASDIC sets.