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

January 1, 1

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.



  • Lab test #NGC6015038




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.

Explore our ceiling product range

Additional acoustics content