An ultrasonic transducer utilizes a unique forward acoustic transmission line comprised of a composite structure partially consisting of a portion of a continuous smooth sheet of material, such as an automobile bumper, from which the acoustic beam is emitted. This makes it invisible to sight, thus allowing for an improved object detection system in which the sensors cannot be seen, so that they do not interfere with the smooth lines that were designed into the surface of the object or vehicle onto which they are mounted. This is a significant improvement for applications where the look and style of the surface of the platform is important, such as in automotive park assist systems.