Method and apparatus for generating low frequency acoustic energy waves

Abstract From the Canadian patent

An acoustic transmitter is employed in a borehole logging tool for generating low frequency acoustic energy waves. A tube of piezoelectric material is sealed at both ends and filled with liquid. A pliable boot surrounds such piezoelectric tube. At least one passageway communicates the inside of the piezoelectric tube with the inner surface of the boot. Differing electrical polarities are applied to the inner and outer surfaces of the piezoelectric tube. These electrical polarities are modulated to excite the piezoelectric tube to resonate at a frequency controlled by the inertia of the liquid in the passageway and the mass of the liquid inside the piezoelectric tube.