International Residential Code 2015 (IRC 2015)

Part I — Administrative

Part II — Definitions

Part III — Building Planning and Construction

Part IV — Energy Conservation

Part V — Mechanical

Part VI — Fuel Gas

Part VII — Plumbing

Part IX — Referenced Standards

Heads up: There are no amended sections in this chapter.
(The provisions contained in this appendix are not mandatory unless specifically referenced in the adopting ordinance.)
Wall and floor-ceiling assemblies separating dwelling units, including those separating adjacent townhouse units, shall provide air-borne sound insulation for walls, and both air-borne and impact sound insulation for floor-ceiling assemblies.
Air-borne sound insulation for wall and floor-ceiling assemblies shall meet a sound transmission class (STC) rating of 45 when tested in accordance with ASTM E90. Penetrations or openings in construction assemblies for piping ; electrical devices; recessed cabinets; bathtubs; soffits; or heating, ventilating or exhaust ducts shall be sealed, lined, insulated or otherwise treated to maintain the required ratings. Dwelling unit entrance doors, which share a common space, shall be tight fitting to the frame and sill.
The sound transmission class of concrete masonry and clay masonry assemblies shall be calculated in accordance with TMS 0302 or determined through testing in accordance with ASTM E90.
Floor/ceiling assemblies between dwelling units, or between a dwelling unit and a public or service area within a structure, shall have an impact insulation class (IIC) rating of not less than 45 when tested in accordance with ASTM E492.
ASTM E90 - 04 Test Method for Laboratory
  Measurement of Air-borne Sound
  Transmission Loss of Building
  Partitions and Elements
ASTM E492 - 09 Specification for Laboratory
  Measurement of Impact Sound
  Transmission through Floor-ceiling
  Assemblies Using the Tapping
The Masonry Society
TMS 0302 - 12 Standard for Determining
  the Sound Transmission Class Rating
  for Masonry Walls
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