Speech Privacy Class calculations and post-construction measurements of a corporate workplace tenant improvement project

LEED interior design and construction projects IEQ acoustical credits are particularly difficult to achieve due to broad scope requirements and restrictive credit language. Specifically, the high composite sound transmission requirement between private offices and hallways. DLR Group acoustical staff proposed an alternative compliance path and evaluation focused on lower STC rated partitions with the addition of sound masking systems to increase the background noise levels, with the goal of achieving an equivalent level of speech privacy between offices and hallways. Speech Privacy Class as detailed in ASTM E2638-10 was used as the evaluation metric. Difficulties in analysis and design stage assessment included unknown level difference of constructed partitions and entry doors, correlating subjective Client expectations to objective SPC ratings, and Client sign-off on sound masking approach. Post-construction measurements were conducted before and after sound masking system installation. Significant improvements in objective SPC ratings were measured, although targeted design goal SPC ratings were not achieved in all cases. Measured noise level differences of the glass storefront office partitions and measured sound masking noise spectra were compared to design stage values for further process refinement. Completed space measurement results and design stage comparisons will be reviewed and discussed.