ANOMALOUS DIRECTIVITY OF A PIEZOELECTRIC POLYMER FILM HYDROPHONE

An irregular phenomenon that arises in the directivity characteristics of a hydrophone utilizing a piezoelectric polymer film as an active e lement is studied. At the radial resonant frequency of a Rayleigh-type surface wave induced on the hydrophone's backing material, a sharp nu ll in the directivity characteristics is observed, as if the hydrophon e apparently has a narrow directivity pattern. This irregularity is sh own to be caused by the interference between an incident wave and a Ra yleigh-type surface wave induced on the backing material.