Ciborowski and Pluemer (1991) discuss noise considerations in an efficient air recirculation system in a semiconductor facility.
During the design phase... in addition to energy efficiency, [a] high priority was given to minimizing acoustic and vibrational contamination of the cleanroom. To achieve these ends, a low pressure ducted HEPA system was designed. In addition, air handler components (cooling coils, filter banks, etc.) were sized for low pressure drop. Vane axial fans and plug fans were the most promising air movers for low energy use. While the vane axial fan was much more efficient [than the plug fan] (88% vs. 53%) for the air flow and initial system pressure, its sound characteristics were such that an external sound attenuation was required to meet the specified sound power levels for the clean space. The increased pressure drop of the attenuators resulted in a system pressure increase that more than negated the benefit of the increased fan efficiency. The plug fans selected required no attenuation because with a low system pressure a large fan wheel (54 in.) revolving at a low speed (450 RPM) would meet the design requirements.
