Determination of acoustic blocked sources in a ventilation duct

A test case is presented demonstrating how to determine representative point sources along the cross-section of a duct that produce the appropriate response downstream even if a downstream modification is made. One end of a duct is attached to a source room with loudspeakers. The source is represented by determining acoustic blocked sources downstream of the source room. These blocked sources are determined along the cross-section of a duct using an inverse approach similar to transfer path analysis. It is demonstrated that these acoustic blocked sources can then be used to predict the response at other positions downstream of the interface at frequencies above the plane wave cut-off both in the original configuration and after a silencer is added. The approach is promising for source identification in HVAC equipment and other low flow applications.