Abstract
A method is proposed to estimate the mechanical properties of materials from the sound produced by the impact of a ceramic or steel sphere on a rectangular bar specimen which is suspended by thin wires or ceramic threads. In this method, we first observe the waveform of the sound produced by the impact. To measure the elastic moduli from the impact sound, we have to estimate the natural frequencies of vibration of the specimen from the obtained time-series of sound waveform. By an impact, the rectangular bar specimen produces the flexural vibration of the horizontal and vertical direction as well as the torsional vibration. For accurate estimation, it is necessary to identify vibration modes as many as possible. In this paper, we employ the frequency analysis and time-frequency analysis of the impact sound. Also, we discuss the information of the impact sound obtained by time-frequency analysis using the short time Fourier transform.
