The Effect of Length on the Insertion Loss of Fiberglass-Lined Sheet Metal Ducts--Part II: Round Ducts

Douglas Reynolds, University of Nevada, Las Vegas
Michael Schwob, Schowb Acoustics, Inc.


This paper discusses results from ASHRAE Research Project RP-1408, which includes tests to quantify the effect of length on the insertion loss of fiberglass-lined round ducts. The results of insertion loss tests are presented for 1 and 2 in. (25 and 50 mm) thick fiberglass-lined round ducts. Further, an analysis of this data with the objective to develop empirical equations to predict the insertion loss is discussed. The equations are presented and compared with prediction methods currently recommended by ASHRAE Handbook--HVAC Applications.