This project involved an early-generation ‘green’ office building, designed with a natural-ventilation system to reduce energy consumption. Such a system requires low air-flow resistance, achieved by large openings in the building structure. Unfortunately, this can cause
problems due to a significant reduction of the noise isolation between workspaces. This problem has been experienced in the Liu Institute. According to the results of an occupant-satisfaction survey, the quality of the acoustical environment in this building is very low, with poor speech privacy—between
the shared offices at the ends of the corridors and their surroundings (in particular, offices on the other floors) and in offices along corridors—being the main sources of dissatisfaction. This project further investigated the acoustical problems by way of relevant physical-acoustical
measurements and acceptability criteria. These confirmed the inadequate noise isolation and speech privacy at the Liu north end due to the natural-ventilation shafts, and between third-floor offices and adjacent corridors, due to partition openings. Subject to applicable ventilation constraints,
measures were designed to increase the noise isolation. In the ventilation shafts, these comprised a sound-absorptive lining and/or suspended sound-absorptive baffles. In the partition opening, it comprised a lined, Z-shaped transfer box. A ray-tracing model was used to predict the performance
and refine the designs. Measurements were made after the noise-isolation measures were installed in the two north ventilation shafts and in a third-floor office, to evaluate their performance. The noise isolation between floors increased substantially; speech privacy was in the confidential
range. The isolation through the partition opening between the office and corridor increased somewhat; however, speech privacy was lower than acceptable. There is evidence that lining the ventilation shafts alone is insufficient, that lining and baffles provide more noise isolation than required,
and that baffles alone would be most cost-effective. The performance of the transfer box was lower than required. The results of air-flow and air-quality tests before and after treatment showed that the changes after treatment were insignificant, suggesting that treatment had little effect
on ventilation and air quality, probably because they were inadequate in the untreated building. The results of the study suggest that the acoustical environment in a naturally-ventilated ‘green’ building can be made acceptable without compromising ventilation quality using the
types of devices designed in this work. However, further work is required to optimize their designs.
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