Measurement of nonlinear acoustic property of solid

The acoustic nonlinear parameter β which characterizes the nonlinearity of materials has been increasingly important for description of material properties. Up to now, most of these studies were worked in progressive wave field by measurement of the second harmonic amplitude. They can´t be used for samples with thickness less than acoustic wavelength, such as the rock sample which is not too large but it is measured in lower frequency. The author has studied the one dimensional nonlinear acoustic standing wave field in a rod, and a new standing wave method for measuring β was suggested, in which the acoustic impedance Z at the interface of transducer and sample was introduced; Z must be determined by experiment. In this paper, we solve the problem of measuring Z and then discuss the distribution of standing wave field of basic frequency, DC component and second harmonic in the rod