Abstract: An apparatus for use down a bore hole to reduce the viscosity of a hydrocarbon-containing fluid in the bore hole. The apparatus includes a housing having a size for disposition in the bore hole. At least one ultrasonic transducer is carried by the housing. The ultrasonic transducer preferably has an active element changeable from a first shape to a second shape in the presence of an electromagnetic field. An electromagnetic field is provided through at least a portion of the active element to change the shape of the active element. An acoustic element is coupled to the active element for providing ultrasonic energy to the hydrocarbon-containing fluid in the bore hole. A method for reducing the viscosity of a hydrocarbon-containing fluid in a bore hole is additionally provided.