Inclusion Criteria:  Neonates between 28 and 40 Weeks of Gestational Age (wGA) Hospitalized in the neonatal intensive care units of the university hospital of Saint-Etienne (France)  Exclusion Criteria:  Respiratory or hemodynamic instability Uncontrolled sepsis Sedation on going Treatment known to modify the sympathetic or parasympathetic activity of the autonomic nervous system Congenital disease Congenital ear pathology