Charles H. Sherman
John L. Butler
Image Acoust., Inc., 97 Elm St., Cohasset, MA 02025
An important goal of electroacoustic transducer development has long been maximization of the acoustic output power for a given transducer size. This goal always encounters familiar material mechanical, electrical, magnetic or thermal limitations---all the ultimate effects of nonlinear behavior. However, other nonlinear effects, such as harmonic distortion and instability, are the practical operational limitation in some applications, making nonlinear analysis an essential part of the process. Most basic transduction mechanisms are strongly nonlinear and all have some nonlinearities. Fortunately, the nonlinearities in all transducers have similar features and can often be represented in identical mathematical forms even when physically different. This study identifies the nonlinear features which are common to all major types of transducers (electrostatic, variable reluctance, piezoelectric, electrostrictive, magnetostrictive, and moving coil). Recognizing these common features makes it possible to develop nonlinear solutions which apply to all types of transducers and facilitates comparison of transducer types for susceptibility to nonlinear effects. Recently published perturbation solutions obtained for moving coil transducers [J. Acoust. Soc. Am. 94, 2485--2496 (1993)] will be generalized and used to illustrate evaluation of harmonic distortion in other transducers.