To date, patients with recalcitrant functional dysphonia (FD) have been examined and treated symptomatically (i.e. the voice itself). Due to a lack of efficacy of conventional voice therapy for this population, the significant QoL impact, and high financial burden for the healthcare system and society, research should urgently focus on the underlying pathogenesis and psychophysiological aspects related to FD and transfer these findings to treatment opportunities (evidence-based practice). Given the laryngeal innervation by the Vagus nerve and the specific psychological vulnerability in patients with recalcitrant FD, dysregulation of the autonomic nervous system (ANS) will be investigated as a potential pathogenetic/psychophysiological underlying mechanism of the voice disorder. Autonomic dysfunction is well founded in the research fields of psychology and psychiatry, but a completely innovative aspect in the field of voice. First, autonomic dysfunction will be investigated with both physiological (e.g. heart rate variability (HRV), skin conductance level) and patient-reported outcome measures (e.g. Neuroception of Psychological Safety Scale, Depression Anxiety and Stress Scale) in a case-control study. Second, the effects of a therapy based on ANS regulation, i.e. HRV biofeedback, will be investigated on both voice function and autonomic function, using a longitudinal randomized sham-controlled trial.