Abstract: A casing is disposed in an oil well and is constructed to provide for the flow of oil in the well. For example, the casing may be cylindrical and may be perforated in its cylindrical wall. The casing is resonant in a hoop mode at a particular fundamental frequency. This fundamental frequency may be in the order of approximately 400 hertz. A transducer includes a transducer member disposed within a tubing in spaced relationship to the tubing. The transducer member may be a ceramic slotted at one end and supported by the tubing at the other end. A ring may envelope the ceramic member and may be slotted at the same position as the ceramic member. The tubing may be filled with an oil which provides dielectric properties and operates to transmit vibrations from the transducer to the tubing. The transducer may vibrate in the hoop mode at the fundamental frequency of resonance of the casing. The transducer member is energized to obtain the production of vibrations in the transducer in the hoop mode.