A transducer model, based on nonlinear piezoelectric constitutive equa
tions, has been developed to describe the harmonic generation that occ
urs on current or velocity signal analysis when the transducer is driv
en at high voltage. The symmetrical Langevin transducer studied close
to its resonance frequency is composed of Navy III type power ceramics
. The nonlinearities create an energy spread over the frequency spectr
um and consequently result in an amplitude saturation effect at the dr
iving frequency, which can be interpreted in terms of the loss mechani
sm. Experiments have been carried out to measure the nonlinear losses
and the harmonic amplitude evolutions. Results are given and discussed
. Eventually, by experimental means, identification of the influential
nonlinear coefficients permits comparison between theoretical predict
ions and experimental results.