In this Letter an alternative method for the experimental determination of the complex acoustic propagation transfer function is presented. The method uses an adaptive filter in system identification mode. The inputs to the system are the source and received signals. The transfer function is represented by finite impulse response filter coefficients. Good results were obtained using filter lengths in the range from 100 to 250 with a sampling rate of 12 k samples/s. The method is outlined and some representative results with experimental field data are given.