Wayne Parham Messages: 18791 Registered: January 2001
Illuminati (33rd Degree)
I have found that adapters formed with straight pipe often create a 1/4λ resonance with frequency set by the length of the adapter. This is particularly true if the interface isn't smooth, or if the flare widens rapidly at the throat. The 1/4λ resonance is also modified by by cross-section area and boundary conditions.