Role of Sleep in Cardiovascular Functions

Inclusion Criteria: * Informed Consent * Good general health status * Male subjects 18-84 years of age * Native German speaker or good understanding of German Exclusion Criteria: * Contraindications on ethical grounds, * Known or suspected non-compliance, drug or alcohol abuse, * Regular medication intake that could pronouncedly affect outcomes of interest (e.g. beta-blocker) * Long (\> 9.5 hours per night) or short sleepers (\< 6.5 hours per night), * Smoking (regular smoker, \>10 days per year, smoking not allowed during study participation) * Participation in another study with investigational drug/therapy/interventions within the 30 days preceding and during the present study (start date adapted accordingly), * Diseases or lesions of the nervous system (acute or residual included neurological and psychiatric diseases), * Clinically significant concomitant disease states (e.g., renal failure, hepatic dysfunction, cardiovascular disease, etc.), * Pacemaker, * Intake of on-label sleep medication, * Presence or suspicion of sleep disorders (e.g., insomnia, sleep disordered breathing (apnea), restless legs syndrome). Possibility of apnea might be assessed in the screening night, * Body Mass Index \< 18 or \> 30 kg/m2, * Irregular sleep-wake rhythm (e.g. shift working), * Bad sleep quality during screening night (e.g. \< 75% sleep efficiency in screening night) * Significant sleep complaints in general or excessive daytime sleepiness (PSQI \> 5; ESS ≥ 11), * Travelling more than 2 time zones in the 2 weeks before experimental session starts or during intervention (start of experiment will be adapted to fit with this criteria), * Hearing disability/ hearing aid (only an exclusion if in a simple audiometry participants cannot hear intervention tone sound levels), * Skin disorders/problems/allergies (face region) that will significantly worsen with electrode application, * High caffeine consumption (\> 5 servings/day; including coffee and caffeinated energy drinks),