DEVICE FOR OUTPUTTING AND/OR RECEIVING ULTRASOUND AND ULTRASOUND SENSOR FOR INSPECTING A VALUABLE DOCUMENT

摘要

An apparatus for emitting and/or receiving ultrasound in a predetermined frequency range includes at least one ultrasonic converter for converting ultrasound into electrical signals and/or converting electrical signals into ultrasound, and a holder having at least one ultrasonic channel formed therein in which the ultrasonic converter is disposed at least partly and/or through which ultrasound can pass from or to the ultrasonic converter. The holder has at least one non-fibrous surface layer adjacent to at least one portion of the ultrasonic channel, whose impedance is smaller than that of an inside layer of the holder neighboring to the surface layer.