Acoustic plaster is plaster

Plaster

Plaster is a building material used for coating walls and ceilings. Plaster starts as a dry powder similar to mortar or cement and like those materials it is mixed with water to form a paste which liberates heat and then hardens. Unlike mortar and cement, plaster remains quite soft after setting,...

 which contains fibres or aggregate so that it absorbs sound

Absorption (acoustics)

Acoustic absorption is that property of any material that changes the acoustic energy of sound waves into another form, often heat, which it to some extent retains, as opposed to that sound energy that material reflects or conducts. Acoustic absorption is represented by the symbol A in calculations...

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Such plaster is applied in thicknesses of up to 1.5 inches. As compared with other sound insulation, it is easy to apply and is fireproof

Fireproof

-Track List for Original 2002 Release:# "Fireproof" – 3:46# "Just 2 Get By" – 4:17# "Echelon" – 3:25# "Stay Up" – 3:40# "Behind Closed Doors" – 2:55# "Epidemic" – 3:14# "Hindsight" – 2:57# "Light at My Feet" – 3:28# "A Shame" – 3:17...

 but it can be more fragile, being affected by physical stress and humidity. Acoustic plaster is used in construction of rooms which require good acoustic qualities such as auditoria

Auditorium

An auditorium is a room built to enable an audience to hear and watch performances at venues such as theatres. For movie theaters, the number of auditoriums is expressed as the number of screens.- Etymology :...

 and libraries

Library

In a traditional sense, a library is a large collection of books, and can refer to the place in which the collection is housed. Today, the term can refer to any collection, including digital sources, resources, and services...

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Proprietary types of acoustic plaster developed in the 1920s included Macoustic Plaster, Sabinite, Kalite, Wyodak, Old Newark and Sprayo-Flake produced by companies such as US Gypsum. These superseded felt

Felt

Felt is a non-woven cloth that is produced by matting, condensing and pressing woollen fibres. While some types of felt are very soft, some are tough enough to form construction materials. Felt can be of any colour, and made into any shape or size....

s and quilt

Quilt

A quilt is a type of bed cover, traditionally composed of three layers of fiber: a woven cloth top, a layer of batting or wadding and a woven back, combined using the technique of quilting. “Quilting” refers to the technique of joining at least two fabric layers by stitches or ties...

s as a common preference of architects but were difficult to apply and so were superseded in turn by acoustic tiles.