Electromechanical impedance (EMI) technique is receiving increasing attention in the area of structural health monitoring (SHM). In this technique, piezoelectric transducer (PZT) is either surface bonded to or embedded inside the host structure to be monitored. The PZT actuates harmonically in the presence of electric field to produce a structural response over a wide range of frequency, which is known as 'admittance signature'. These signatures serve as indicator to predict the health of the structure, any change in the signature is indication of presence of damage or other degradation in the structure. Sometimes the raw data associated with the applied frequency range is in excess of necessary data. In the present paper, an EMI based experimental study was conducted on steel, aluminum and concrete specimens to monitor load, crack and curing respectively for various frequency ranges. Admittance signatures of specimens were acquired for a wide frequency range of excitation. Later, statistical index was adopted to measure and compare the sensitivities for various narrower ranges within the wide frequency range. Additionally a novel signature gradient was used to characterize signatures at each frequency. Thus in this study an evaluation of sensitivity of EMI technique for various frequency bands to monitor load, crack and curing process was carried out in order to find out necessary frequency band suitable form wide frequency range. It is demonstrated that this approach can be applied to real structures and an initial assessment can be made to eliminate unnecessary data acquisition.