ABSTRACT
The previous chapter was concerned solely with piezo-electric materials and the manner by which they are incorporated into an ultrasonic transducer. Having considered the internal structure of a transducer, the ultrasonic elds radiated by such a device are now presented. This chapter begins with an examination of continuous wave (CW) excitation, and specically that from a circular plane piston source. Whilst the predicted eld for this type of source is well known, it is of limited use in medical ultrasonics. Non-focussed physiotherapy devices are about the only devices that produce CW elds from a circular plane piston transducer. Despite these limitations, however, CW solutions are an instructive starting point as they introduce concepts that are useful in the study of more complex elds. The CW eld produced by rectangular transducers is also presented.
