Assessment of HVAC-related background noise in offices. Accuracy of single number parameters against spatial distribution of sound

Acoustic design must ensure the HVAC noise to be sufficiently low and unobtrusive in quality, so as it does not interfere with requirements for occupant use. For instance, when background noise reduces speech intelligibility, productivity can be lost. Accordingly, LEED, WELL and BREEAM quality protocols propose for rating HVAC-related background noise parameters as SPL, NC and RC. The work aims to determine how significant single-number parameters are to the spatial distribution of perceived loudness and sound quality, considering that HVAC-related noise primarily propagates from supply air system's path or breaks out through ductwork. Simulations were performed on rooms of an office building, of the same intended use (open office) but different in volumes, which comply with protocols guidelines. Spatial distribution of SPL, NC and RC was analyzed, to evaluate the necessity to impose compliance, in addition to an average value, with thresholds at significant points. The impact of radiative noise contribution of the mechanical equipments on single number parameters and maps was estimated, considering the difficulty in simulating it compared to airborne noise. Identified background noise levels were adopted to understand how STI and derived parameters vary in open-offices and ratings following quality protocols and intelligibility standard were compared.