Sound transmission class

Sound Transmission Class (or STC) is an integer rating of how well a building partition attenuates airborne sound. In the US, it is widely used to rate interior partitions, ceilings, floors, doors, windows and exterior wall configurations. Outside the US, the ISO Sound Reduction Index (SRI) is used. The STC rating very roughly reflects the decibel reduction of noise that a partition can provide. The STC is useful for evaluating annoyance due to speech sounds, but not music or machinery noise as these sources contain more low frequency energy than speech.[1]

There are many ways to improve the sound transmission class of a partition, though the two most basic principles are adding mass and increasing the overall thickness. In general, the sound transmission class of a double wythe wall (e.g. two 4-inch-thick [100 mm] block walls separated by a 2-inch [51 mm] airspace) is greater than a single wall of equivalent mass (e.g. homogeneous 8-inch [200 mm] block wall).[2]

  1. ^ Roller, H. Stanley (November 1985). "Isolating music and mechanical equipment sound sources with gypsum board partition systems". The Journal of the Acoustical Society of America. 78 (S1): S10. Bibcode:1985ASAJ...78...10R. doi:10.1121/1.2022641. ISSN 0001-4966.
  2. ^ Egan, M. David. (2007). Architectural acoustics. J. Ross Publishing. ISBN 978-1-932159-78-3. OCLC 636858059.