The radiated pressure fields of axisymmetric ultrasonic transducers have been measured experimentally at a single frequency to a high resolution. Results in both the nearfield and farfield have been compared to the prediction of theory in three dimensions, developed to examine transducers vibrating with an arbitrary amplitude and phase distribution across their front face. Good correlation was obtained for polyvinylidene fluoride (PVDF) radiators, assuming plane-piston-type behavior. For lead zirconate titanate (PZT) transducers, marked amplitude variations with radius across the disk face were encountered, and these needed to be modeled theoretically to obtain good agreement with experiment. Other predictions of theory which are of interest to applications involving acoustical imaging are presented.
It is well established that the field from uniformly vibrating piston transducers may be considered as being derived from two components: a plane wave and an edge wave. These have been both predicted and observed in practice, but it would seem that a mathematical expression for the edge-wave component has not yet been developed fully. In this article, expressions are developed for the pressure and particle velocity edge waves that can be used to calculate the field that results when a plane wave is diffracted by an edge. The expressions are used to study a particular example, namely, that of an arbitrarily shaped piston radiator. The results for certain situations are shown to agree with existing solutions for a disk source.
The transient pressure fields of ideal planar ultrasonic transducers may be described in terms of plane and edge wave contributions. Based on this concept, a technique is developed which allows characterization of wideband unfocused transducers by a single measurement close to the transducer face. This method is examined experimentally for both polyvinylidene difluoride and commercial PZT transducers. Also investigated is the effective radiated frequency of these devices.
The radiated pressure fields of pulsed polyvinylindene difluoride (PVDF) transducers have been determined experimentally, and compared to theory in three dimensions. The tranducers were in the form of disks, cones, or bowls, excited with a range of known transients in the form of gated sinusoidal voltages. It is demonstrated that good agreement is possible between theory and experiment, and it is shown that more marked interference effects occur as the duration of excitation tone burst is increased. It is also shown that PVDF transducers may be manufactured so as to behave as plane piston radiators.
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