An investigation of HVAC directivity: theory versus reality 2.0

摘要

Urban densification is the ambition of the Province of Ontario's Places to Grow Act of 2005. Densification requires that high-rise condominiums co-exist in close proximity with one another, as well as neighboring with mixed use commercial or industrial facilities. Rooftop HVAC and air cooled chiller units are common installations for these buildings and are increasingly becoming an environmental nuisance subject to noise control engineering due to proximity and continuous mechanical noise generated during cooling demand.In reality, noise sources do not often radiate sound uniformly in all directions. Corrections are made to account for noise propagation that is both amplified and reduced according to the directivity character defined for that source. To evaluate practicable noise control requirements at the design stage, HVAC units should not be treated as simple noise sources that emit noise in a spherical or hemispherical pattern.This paper suggests that the technical resources that exist for estimating stack or duct directivity are not be representative of HVAC equipment, which generates significant sound from the condenser fans in the vertical direction, and the compressors in the horizontal direction.Our May 2014 paper on this topic presented at the September 2014 Noise-Con conference provided proposed directivity for HVAC units. We have subsequently conducted further field testing to confirm the proposed directivity corrections.