Scaled down measurement of HVAC duct insertion loss and comparison to simulation

Acoustical consultants and noise control engineers regularly rely on the duct attenuation information in the American Society of Heating, Refrigerating, and Air-Conditioning Engineering (ASHRAE) Handbook. The handbook provides duct attenuation on a per length basis in octave bands for a set of standard duct cross-sections. However, acoustical consultants desire additional frequency resolution. Moreover, the handbook is limited to lining thicknesses of either 1 in (2.5 cm) or 2 in (5.1 cm). To fill in some of the gaps in the handbook information, the finite element method is used to determine the insertion loss of rectangular duct cross-sections with wide aspect ratios in 1/3-octave bands on a scaled down version.