In situ calibration of acoustic emission transducers by time reversal method

Conventional methods of calibration of acoustic emission transducers require an already calibrated reference transducer and/or special test specimen. Moreover the calibration results are not directly transferrable to practice, since they are dependent on bonding conditions and mechanical properties of the medium. In this paper a reference-free in situ calibration method is proposed. It is based on a combination of time reversed acoustics and reciprocal calibration and allows accurate determination of transducers' frequency responses. The method was developed and successfully experimentally verified assuming that frequency response of used transducers is the same for transmission and reception. Subsequently the analysis was extended considering irreversible transducers and applied to experimental data. Of five tested transducers, three were found reversible and two demonstrated resonance frequency shift in lower frequency region between reception and transmission.