A mode-match method was developed for calculating the sound propagation in two-dimensional lined rectangular flow duct with uniform flow
the prediction results agree well with the data from NASA flow duct facility and CAA calculation.Based on these
an unknown impedance extracting is implemented by applying changed-scales method to optimize object function or by pursuing a minimum of object function in a given region.The two methods are validated by some cases and the effects of random error and the number of input pressure on the results are analyzed.