1. Department of Audiology and Phoniatrics, Charité-University Medicine Berlin, Campus Charité Mitte, Chariteplatz 1, D-10117 Berlin, Germany
2. Max-Planck Institute for Plasma Physics, Wendelsteinstraße 1, D-17491 Greifswald, Germany
3. ENT Department, University of Greifswald, Fleischmannstraße 8, D-17475 Greifswald, Germany