An experiment based method is proposed for parameter estimation of a class of linear systems. The method was applied to absorption properties of composite material. The material measurements were based on a two-microphone transfer-function method according to ISO 10534-2 and ASTM E1050-98 international standards, which is for horizontally mounted orientation-sensitive materials. The testing apparatus was part of a complete acoustic material testing system, featuring Bruel&Kjaer PULSE (TM) interface. During measurements, system data is taken from testing apparatus by another computer to make parameter identification. Experimental time domain input/output data was utilized in a gray-box modeling approach. Prior knowledge of the form of the system transfer function matrix elements is assumed to be known. Continuous-time system transfer matrix parameters were estimated in real-time by the least-squares method. Simulation results of experimentally determined system transfer function compare very well with the experimental results. The proposed method can be implemented conveniently on a desktop PC equipped with a data acquisition board for parameter estimation of absorption properties of composite material. In this study plastic based composite 0 - 800 Hz between the results of measuring the sound absorption modeling in the Matlab program is presented.