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STC, Flanking Noise, and soundPATHS Commonalities?

9/02/2016

Today's builders, architectural designers and building owners face increasing demands to control growing noise levels within residential and commercial buildings. According to Noise Free America, there has been an increase in occupant noise complaints. The increase in occupant noise complaints and even legal action is due in part to the challenge of translating laboratory tested noise control assemblies to the field.

Over 50 years ago, Sound Transmission Class (STC) ratings were introduced to the building industry. The goal was to provide builders, architects, and acoustical consultants a method of accurately measuring and rating the acoustical performance of individual assemblies tested in a laboratory environment. From these ratings, designers select the assemblies best suited to the specific noise control needs of the building or space.

The issue that designers and builders face is how to translate laboratory measurements and manage noise control performance in the field, where individual wall, floor, and ceiling assemblies are connected to form the building structure. Often, it is the acoustic interaction between field installed wall, floor, and ceiling assemblies that introduce unintended STC or IIC (Impact Insulation Class) results. Unintended results may be due to the selection or STC mismatch of adjacent assemblies, but it is the connection details between these assemblies that make all the difference. The influence and flow of sound energy around a partition assembly, due to its' adjacent wall, floor, or ceiling connections is called "flanking noise". Flanking noise can often become the make-or-break point in determining whether an intended noise control solution will be successful in the field.

So the question arises, how can builders, architects, consultants and building owners reduce their risks and overcome the gap between laboratory tested assemblies and field performance?

The National Research Council of Canada (NRC) and a consortium of sponsoring companies, including Owens Corning, USG, Trus Joist (now Weyerhaeuser), Forintek Canada Corporation, and Canada Mortgage and Housing Corporation (CMHC), initiated a testing program to better understand the effects of flanking noise. This work focused on the STC and IIC ratings of laboratory tested assemblies under field conditions. The NRC built a facility specifically designed to test the influence of flanking noise on full room assemblies, both in the horizontal and vertical direction.

Over more than ten years of comprehensive testing and collaborative work, incorporating numerous types of wood frame wall, floor, and ceiling assemblies, resulted in the "Guide for Sound Insulation in Wood Frame Construction" (NRC report #: IRC-RR-219).

Subsequent to the publication of this comprehensive report, the consortium reconvened to continue their efforts with NRC. The goal now was to leverage information from the testing phase to develop a predictive interactive electronic design tool.The tool allows architects, consultants, and builders to directly choose specific assemblies and build "virtual room structures" that reveal the influences of flanking noise on laboratory tested STC assemblies. One can quickly begin to see a number of design options, features and structure (connection) details that reveal the benefits of controlling flanking noise.

Called "soundPATHS", the interactive program leads the designer through a number of options that compare laboratory STC results to that same wall when influenced by flanking noise. Apparent Sound Transmission Class (ASTC) is the noise control performance rating that includes the effects of flanking noise on wall, floor, or ceiling assemblies. The ASTC rating predicts actual noise control performance of an assembly when built as a combined wall, floor, ceiling structure.

I recommend you take a moment to check out this relative new program. Though still in its early stages of development, it can provide building design insights that may prevent the unexpected onset of noise control issues, resulting in better building practices and fewer customer complaints. Click here for online access to soundPATHS.

Related Tags: Performance | Acoustic