Absolute sensitivity limits of various ultrasonic transducers

We compare the calculated and measured sensitivities of wide-band, ultrasonic transducers: optical interferometers, air-coupled capacitive transducers, electromagnetic acoustic transducers (EMATs), and contact piezoelectric transducers. In the case of ideal (lossless) sensors we find that air-coupled, EMAT and contact piezoelectric sensors all exhibit increased sensitivities over that of optical transducers. We then describe a procedure for measuring such sensitivity limits and validate the procedure by determining the sensitivity limit of a contact piezoelectric transducer