Transducer forming compression and shear waves for use in acoustic well logging

Claim 1

Acoustic wave generating apparatus comprising: (a) radially directed expansion means including N expansion means elements in number where N is an integer, and wherein said expansion means elements move radially directed outwardly and inwardly, said radial outward and inward movement being relative to a center line, and through a selected stroke length to thereby deflect an attached transducer outer face, said expansion means elements forming a stroke of selected amplitude and frequency to create an acoustic wave, wherein the acoustic wave is a compression or shear wave depending on the relative phase of operation of said expansion means when placed in a well borehole; (b) coil means wrapped around an elongate, radially directed magnetostrictive element comprising said expansion means elements; (c) N driver amplifiers, one being connected to each of said elements, and all are provided with a driving signal from a signal generating means to form acoustic waves dependent on the driving signal; and (d) polarity selecting means connected to each of said amplifiers to time operation of said amplifiers and thereby time formation of acoustic waves from said transducer outer faces wherein changes in timing cause the acoustic waves to be compression or shear waves.