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Learn about Acoustical Drywall

Acoustical Drywall

Acoustical drywall typically consists of a layer of viscoelastic polymer sandwiched between two thin layers of regular drywall (gypsum board). It is used for interior wall and ceiling surfaces to reduce the transmission of sound between living spaces in a building.

The ability for acoustical drywall to reduce sound transmission is rated by its STC (sound transmission class). The higher the STC the better, and acoustical drywall has an STC of about 47-52. At a value of 50 STC, only very loud sounds such musical instruments can still be faintly heard. Note that the STC rating does not apply to low frequency sounds like bass sounds from a home theater, truck or airplane traffic, and musical instruments like a bass or drums. To eliminate these sounds it may be necessary to add an additional layer of drywall. Look for low-VOC or no-VOC products. Because of the extra layer of drywall, acoustical drywall cannot be cut with a knife like regular drywall. Instead, a saw must be used, making the installation costs much higher.

Acoustical drywall can help achieve higher density living without sacrificing comfort. For example, it can help reduce sound between two apartments in a house with multiple units; or it can help reduce noise between an entertainment room and a bedroom in a house with a small footprint.

STC (sound transmission class) was invented in 1961 to classify the sound transmission through various door, window and wall assemblies.