Acoustic characteristics of fiberglass-lined circular ducts

Fiberglass lined circular ducts are circular ducts with an outer spiral metal shell. They are either dual-wall or single-wall. They have been acoustically treated and are intended to be used in heating, ventilation and air conditioning (HVAC) duct systems to reduce the amount of sound that is generated by the operation of the components of the system.;To quantify the amount of the sound energy that can be attenuated by a given fiberglass lined circular duct, its acoustical performance has to be determined. Acoustical performance of lined ducts can be experimentally determined in an acoustical laboratory under controlled conditions. These results tend to be more accurate and reliable than those obtained by theoretical equations. HVAC designers need this performance data based on actual test results in order to select the appropriate lined duct for solving noise problems in air handling systems.;The objective of the thesis is to provide the techniques and procedures for measuring the insertion loss (with and without airflow) of fiberglass lined circular ducts. Regression analyses were conducted on the measured insertion loss data in order to provide regression equations that predict the performance of fiberglass lined circular ducts. Insertion loss tables were generated using these regression equations. (Abstract shortened by UMI.)...