The physical insight of the source data of two-port acoustic source model for a duct is studied in theoretical, experimental and numerical aspects respectively. Under the ideal acoustic boundary condition of full absorption at the duct ends, the state equation of two-port acoustic source model is discussed, and the physical insight of the source data is obtained through theoretical derivation. The experimental model of two-port acoustic source is established, and the source data have been measured by the method “with an external source”. The physical meaning of source data has been demonstrated through the experimental method. The numerical simulating model for the experiment system is built, and the source data obtained numerically are compared with those measured experimentally for research. From the comparison, it is concluded that the source data of two-port acoustic source model are the traveling wave propagating outside along the duct under the acoustic boundary condition of full absorption at duct ends.