Akoustolith is a porous ceramic material resembling stone. It was used to limit acoustic reflection and noise in large vaulted ceilings. The most prevalent use was to aid speech intelligibility in cathedrals and churches prior to the widespread use of public address systems. Akoustolith was bonded as an additional layer to the structural tile of the Tile Arch System ceilings built by the Raphael Guastavino Company of New Jersey. Akoustolith was a patented product of a collaboration between Rafael Guastavino and Harvard professor Wallace Sabine over a period of years starting in 1911.