From a comparison of {HEAD ~ the vibration spectrum} of the flexural mode and {TAIL ~ the vibration spectrum} of the torsional mode , it can be observed that more high harmonic force components are excited in the torsional mode with better signal to noise ratio 
From a comparison of { HEAD ~ the vibration spectrum } of the flexural mode and { TAIL ~ the vibration spectrum } of the torsional mode , it can be observed that more high harmonic force components are excited in the torsional mode with better signal to noise ratio
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH