soundPATHS: Web application to predict sound transmission between rooms

Overview of the application

The National Research Council’s (NRC) soundPATHS web application is a prediction tool for the calculation of direct and flanking sound transmission between adjacent rooms. The software uses the calculation procedure outlined in the 2015 edition of the National Building Code of Canada (NBC).

Direct sound transmission is transmission between two rooms through the separating assembly, e.g. a wall or floor, and is usually classified in terms of Sound Transmission Class (STC). Flanking sound transmission is transmission between two rooms by paths other than directly through the separating assembly. The combination of direct and flanking sound transmission yields the apparent sound transmission, which is classified in terms of Apparent Sound Transmission Class (ASTC) and is used in the 2015 edition of the NBC.

The sound insulation perceived by occupants correlates well with the ASTC rating. The ASTC depends on the construction details of the walls, the floors, and their junctions.

Benefits to users

In soundPATHS, sound transmission between two rooms is presented for each junction, highlighting the weakest and the strongest paths by which sound is transmitted. The weakest path shows the user which building element needs to be improved in order to increase the apparent sound insulation. The strongest path identifies building elements that are overdesigned and where building material can be saved without affecting the apparent sound insulation.

The calculation method used in soundPATHS follows the requirements in the 2015 edition of the National Building Code of Canada. Results from the application may be presented to building officials as proof of compliance with the Code.

Targeted audience

  • Builders/contractors
  • Suppliers/manufacturesr
  • Designers/architects/engineers
  • Building owners/managers
  • Homeowners/General public
  • Building/fire/plumbing officials
  • Others

Description of the application

The expected sound transmission ratings are presented for each construction. Trends are shown to provide a framework for design estimates. Detailed drawings and specifications are presented on the report pages of soundPATHS.

It should be understood that some variation is to be expected in practice due to changing specific design details, workmanship, substitution of "generic equivalents", or simply rebuilding the construction.


The software is provided free of charge.

Contact us

For technical inquiries:

Dr.-Ing. Markus Müller-Trapet, Research Officer
Telephone: 613-993-9748


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