Preterm newborn sleep deprivation due to medical interventions and environmental characteristics of the Neonatal Intermediate Care Unit (NICU) can increase morbidity and developmental deleterious effects. The aim of this study is to test the effect of earmuffs on sleep pattern of preterm neonates. Prospective, randomized, controlled, crossover study conducted in NICU of two teaching hospitals from São Paulo, Brazil. The effect of earmuffs use was analyzed through polysomnography measurement during four "Quiet times" periods. It was also analyzed sleep related variables during 24 hours of the day. Preterm newborns characteristics and clinical characteristics were also analyzed.

Inclusion Criteria:

• Preterm Newborns inside the incubator;
• Preterm Newborns clinically stable;
• Preterm Newborns with no change in hearing screening test;
• Preterm Newborns current weight between 1200 and 2000g.

Exclusion Criteria:

• Preterm Newborns in phototherapy;
• Preterm Newborns in use of invasive mechanical ventilation and noninvasive;
• Preterm Newborns with any type of congenital malformation;
• Preterm Newborns with periventricular hemorrhage grades II, III and IV;
• Preterm Newborns that received Central Nervous System depressant medication and sedative opioid analgesics in the last 24 hours;
• Preterm Newborns using corticoids;
• Preterm Newborn whose mother has a history of illicit drug use during pregnancy