1. Voice Research Lab, Department of Biophysics, Faculty of Science, Palacký University Olomouc, 17. listopadu 12, 771 46 Olomouc, Czech Republic;
2. Department of Otolaryngology, Head and Neck Surgery B53, Clinical Sciences and Intervention, Karolinska Institutet, Karolinska University Hospital, 141 86 Stockholm, Sweden;
3. Voice Centre Stockholm AB, Zangger Vocal Art, Box 4342, 102 67 Stockholm, Sweden