BUILDING SCIENCE

Design and Commercialization Support for New Sound Transmission Requirements

By Berndt Zeitler

NRC is working with clients on investing in research and technology development intended to provide industry with better tools to control sound transmission in multi-family dwellings.
Noise is a pervasive problem in society, with an increasing incidence of complaints by neighbours and demands for effective control measures. This includes both airborne sound and impact noise resulting from footsteps, jumping and the dropping of objects. The ability of a construction system to control noise has a direct bearing on the market acceptance of that system for multi-family dwellings. NRC is working with manufacturers and designers to develop cost-effective solutions for providing enhanced sound control, while incorporating innovative products and systems.

New Requirements for Airborne Sound
Steering committees are currently discussing possible modifications to address comments made during the public review phase (see Construction Innovation, December 2012). The proposals, if accepted, will see the inclusion of a rating that reflects the acoustical performance of the complete building system (Apparent Sound Transmission Class or ASTC). The ASTC is a truer measure of the actual sound level perceived by occupants than the current requirement (Sound Transmission Class or STC) for the direct transmission only through the separating element, as it includes flanking noise (transmitted through wall, ceiling and floor junctions). The control of flanking noise is complex, requiring careful attention to detail around those junctions.
These revised requirements, once approved, will be published in the 2015 edition of the National Building Code. Designers and builders will be in a position to create dwelling-unit assemblies of walls and floors with acceptable sound ratings, while reducing the costs of compliance. Through research projects and technical services, we will help manufacturers take advantage of new opportunities to develop the products and systems these professionals will need.
Companies developing products using common materials (wood, steel, concrete, concrete masonry, insulation, gypsum board, flooring) as well those devising innovative sound-control technologies (resilient clips, hangers, acoustical underlay) need design solutions and compliance assessments. Our researchers are working with NRC evaluation experts and code specialists to help industry clients create technical criteria, assessment methods, and design guides that will be an integral part of the process. A convenient online software tool is also in the making to allow designers to demonstrate compliance.

Impact Noise Control
While protection from airborne noise transmission is the current regulatory priority, work on impact noise-the main source of marketplace complaints-is advancing. Design solutions and assessment criteria to support manufacturers are being developed, and will be made available for inclusion in future code revisions. Attention is being paid to creating uniform requirements and reducing overdesign. We are also helping industry develop requirements and improved technologies for the protection of dwelling units from exterior noise.

Dr. Berndt Zeitler is a Group Leader, Acoustics, at NRC Construction. For more information on NRC's Design & Commercialization Support for New Sound Transmission Requirements, contact Berndt Zeitler at berndt.zeitler@nrc-cnrc.gc.ca or 613-993-9744.

This article has been reprinted from Construction Innovation, (Volume 18, Number 3) with permission from the National Research Council of Canada.