Abstract: The sensitivity of a buried electrostatically charged cable transducer, such as an electret cable, to mechanical disturbances caused by men, vehicles and the like moving on the surface of the ground is greatly improved by disposing the cable loosely in a coextensive rigid hollow member such as a tube. The inside dimension of the tube is larger than the outside diameter of the cable, the cable being supported on the inner surface of the tube at longitudinally randomly spaced points. The cable is thus free to move radially relative to the tube in response to pressure waves or vibrations propagating through the ground and incident on the exterior of the tube so as to bend, twist, compress and/or otherwise stress the cable and generate corresponding electrical signals between the inner and outer conductors of the cable.