Good Blocking (STC 40) – Ceiling Alone (Not Advised)

Due to the many drawbacks, attempting to achieve a STC 40 level of blocking with a modular, acoustic ceiling alone is not advised. First, you would need ceiling panels with a minimum CAC 40 rating and a high NRC rating (0.70 or higher). There are limited options for this level of performance. Second, is the problem controlling noise leaks through the ceiling due to lights, air devices and other elements. Testing conducted by Rockfon and NGC Testing Services¹ shows that these noise leaks can decrease the CAC of the ceiling system by 10 points.

CEILING SYSTEM

• Chicago Metallic® suspension systems
• Noise control measures for noise flanking paths through lights, grilles, diffusers – required CAC 43

• Lab test #NGC6015038

WALL ASSEMBLY

• 1/2" gypsum board (type X) – 1 layer each side
• 3-5/8" steel studs (25 gauge) spaced 16" on center
• 1-1/2" thick ROCKWOOL AFB® Semi-Rigid Batt Insulation
• STC 40 (lab test² # TL-93-343)

Sources

_{1 Madaras, G. and Heuer, A. (2015) "Effects of Noise Flanking Paths on Ceiling Attenuation Class (CAC) Ratings of Ceiling Systems and Inter-Room Speech Privacy." Proceedings of Inter-Noise 2015, edited by Courtney Burroughs and George Maling, paper in15_083, San Francisco, CA, 9-12 August, 2015. Electronic publication.
2 The referenced laboratory test(s) are part of an extensive, multi-year, testing program conducted by the National Research Council Canada (NRCC) and published by the Institute for Research in Construction (IRC). For more details, including 1/3 octave band transmission loss data, refer to internal reports IRC-IR-693, October 1995 and IRC-IR-761, March 1998. The research program was partially funded by ROXUL, Inc. ROCKFON and ROCKWOOL are subsidiaries of the ROCKWOOL Group.}