Bispectrum analysis for impact sound of composite materials

A method to estimate the elastic moduli of a composite material by the sound that occurs at an impact on the composite material was proposed in the field of the material engineering. To estimate elastic moduli from the impact sound, we have to estimate the natural frequencies of the vibration of the material from the obtained time-series waveform. In this report, we show that the natural frequencies of the vibration of the composite material can be estimated by the bispectrum analysis more clearly than the power spectrum analysis.