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Abstract
Owing to the reason that multiple reflection waves are unable to separate, and transfer function and time-delay spectrum are developed, adhesion interface characteristic of the thin layer medium is difficult to detect. Acoustics characteristic of the thin layer is studied with the ultrasonic longitudinal testing method to solve this problem. The results show that the fundamental acoustic parameters of the thin layer, such as sound velocity, reflection coefficient and attenuation coefficient, are obtained based on transfer function and time-delay spectrum. The analytical results show that these parameters mentioned above can characterise adhesion interface quality of the thin layer. The maximum values of the transfer function are unchanged, and its curve is flatter with the increasing of the reflection coefficient. The maximum delayed time increases with the increasing of the reflection coefficient, and the maximum delayed time is more sensitive to the reflection time coefficient variation than the transfer function is.