Detecting Contact-Type Cracks by Modulation Spectroscopy of Acoustic Waves

We studied the characteristics of sidebands in modulation spectroscopy of high-frequency wave due to the disruption of contact-type crack agitated by low frequency, high-amplitude vibration. We developed a close form of sideband amplitude is obtained by convolution of high frequency probing wave with harmonics of pulse wave. This study also proposes an experimental procedure based on sideband phases for determining the crack parameters.