The present invention relates to a packaging machine having an ultrasonic device (1), the ultrasonic device (1) comprising: an ultrasonic generator (2) which generates electric vibrations; an ultrasonic converter (3) which converts the generated electric vibrations into mechanical vibrations of the same frequency; a transformation intermediate piece (4) which transfers the mechanical vibrations to a sonotrode (5); the sonotrode (5) comprising a sound-radiating end surface (6) at which it reflects the mechanical vibrations, so that a standing wave to be passed into a packaging foil (18, 19) is formed, and the sound-radiating end surface (6) being disposed in a vacuum and/or in a modified atmosphere.