Abstract: With ultrasonic echo testing method, the characteristic of rubber thin layer is investigated. The theory of surveying the thin layer medium characteristic with frequency spectral analysis is deduced. A method is proposed to establish restoration function of frequency spectrum ratio of ultrasonic echoes under the condition of substrate material covered and uncovered with the rubber thin layer. The results show that H(f ) contains information on the acoustic properties of the substrate and the thin layer, not only the supersonic wave propagation velocity in the rubber thin layer can be acquired, but also the acoustic impedance of thin layer and density. This method can test the characteristic of the thin layer material without damaging its service performance, the results of which accord with the time frequency composite field analysis method.

Key words: Acoustic impedance, Restoration function, Rubber thin layer, Ultrasonic testing