Abstract: A transducer which uses paramagnetic magnetostrictive rods or bars, e.g., compositions of the lanthanide series of elements such as Tb.sub.0.3 Dy.sub.0.7 Fe.sub.2, has the bars biased with a lengthwise flux by a permanent magnet, e.g. samarium-colbalt, of high resistance to demagnetization by the alternating field applied to the bars by alternating current in a coil surrounding the bar. The magnet is outside the coil to reduce the ac field to which it is subjected. Uniformity of flux density along the length of the bars is enhanced by having adjacent ends of the bars subjected to like-polarity poles of the permanent magnets associated with each bar.

Abstract: A rod of magnetostrictive material has its ends placed between steel bars which provide compression on the rod by tensioning wires connected between the bars. Preferably, the wires are equally spaced along the bars from the rod so that when the wires are equally tensioned the rod is under no bending stress. The tension of the wires (and from this value, the compression of the rod) is conveniently determined by the freqency of vibration of the wires using known physical relationships between these quantities.