Investigating the absorption characteristics of open ceilings in multi-purpose halls using a 1:25 scale model

This paper investigated the absorption coefficients of acoustically transparent ceilings using 1:25 scale models. From a field survey of 18 existing halls, it was found that the open ceilings were equipped with steel truss structures, ducts, catwalks and ceiling surfaces. In order to investigate the absorption characteristics of the equipped ceilings, measurements were made using a 1:25 reverberation chamber based on ISO 354. Results showed that for an empty ceiling with a depth of 6 m, the absorption coefficient with a 50%-perforated ceiling surface is 0.2–0.3 above 500 Hz. If there were steel structures inside the ceiling, the absorption coefficient increased by 0.1 at 125 Hz to 2 kHz. Adding ducts and catwalks increased the absorption by 1–2 kHz. The absorption coefficients of the equipped ceilings ranged from 0.19 to 0.61 and the absorption characteristics were mainly found at high frequencies. Maximum absorption was observed in heavily equipped ceiling structures.