Impedance characteristics of transducers and reciprocity calibration
Li-Feng Ge · The Journal of the Acoustical Society of America · 1989
This paper investigates impedance characteristics of electrodynamic-type and piezoelectric-type transducers. The inherent relation between mechanical impedance of a mass load and electrical impedance of the transducing element of transducers is revealed. The substance of reciprocity calibration is just to utilize the impedance inversive property of both types of transducers so that one can determine the mechanical quantities (force and velocity) by measuring electrical quantities, which can be measured conveniently and accurately. According to the theory, for high-frequency calibration, mass values in the reciprocity calibration formulas should be replaced by their equivalent masses rather than static mass values, because the mechanical impedances of mass loads will be remarkably changed due to the stress wave effect. Making the correction can improve calibration accuracy by about one-half order of magnitude.