RP-1026 -- The Aero-Acoustic Properties of Common HVAC Plena
The HVAC plenum is commonly applied as a means to reduce problematic low frequency noise produced by mechanical equipment in ducted systems. Its predicted acoustical performance has been derived from an earlier investigation. This early work did not focus on low frequency performance, the effects of wall linings or typical HVAC geometric variables. Through the ASHRAE sponsored research project (RP-1026), conducted by Vibro-Acoustics, rigorous testing enabled the identification of comprehensive attenuation properties for common HVAC plena. A two-stage prediction approach resulted, which applies an improved version of the current equation for mid-tohigh frequency attenuation, quantified as a Transmission Loss [TL] , and a surface area and wall characteristic model for the critical low frequency TL. This method has improved the prediction accuracy of flow-through type HVAC plena with a volume range of 201100 ft3 (0.5-30 m3). In addition, this work has identified acoustical effects for seven different wall- lining systems and typical geometric variables, such as opening offsets, opening area ratio variables, and multiple openings. Finally, this research has also quantified resulting total pressure drop performance for a ducted plenum for the same geometric variables used in the main acoustical portion of the study.
Product Code(s): D-21504
