Run final acoustical mechanical background noise calculations and determine the final STC ratings for the appropriate building assemblies (if applicable). Verify that the project goals are met.
Specify windows with an STC rating of 35 or greater.
Meeting the background noise level requirements typically will bring a minimal cost increase due to upgrades in mechanical equipment and calculations. There could be a substantial cost increase if a redesign with upgrades is necessary.
The mechanical engineer should work with an acoustics consultant, or closely with the manufacturer, if they are not familiar with these installation and calculation issues.
It may be difficult to appropriately calculate the effectiveness of duct silencers. It is important to select an appropriate silencer and to place them properly within the ductwork layout.
Calculations for “duct breakout noise” should also be made if there is large, high-velocity ductwork in the core learning space or above lay-in tile ceilings. Acoustic duct lagging may be needed in these situations.
Ductless mechanical systems or open-plan classrooms will most likely not conform to the background noise level requirements of this credit.
Follow recommendations based on these preliminary calculations or assessment, including acoustical changes integrated by the mechanical engineer into mechanical plans and project specifications.
Depending on the compliance path selected:
Run preliminary calculations calculated by the acoustics consultant or mechanical engineer, as defined by the 2007 HVAC Applications ASHRAE Handbook, Chapter 47, Sounds and Vibration Control and determine any design changes needed for compliance.
Follow the design recommendation in ANSI S12.60-2002 and determine any design changes needed for compliance.
The mechanical engineer, in collaboration with the acoustics consultant, design compliant mechanical systems and a delivery system that will meet the LEED credit requirements of 40 dBA or less, at maximum operating conditions.