Background Caring for premature infants in the Neonatal Intensive Care Unit (NICU) involves several challenges, including exposure to excessive environmental noise, which can cause stress and disrupt sleep. This study aimed to evaluate the effects of sound-absorbing incubator covers on physiological responses, sleep patterns in preterm infants, and incubator noise levels. Methods A randomized controlled crossover trial was conducted involving 40 medically stable preterm infants in the Perinatology Room of a hospital in Jakarta, Indonesia. The intervention group received a sound-absorbing incubator cover, while the control group received a standard cover. Physiological responses and sleep patterns were assessed using the Anderson Behavioral State Scale (ABSS). Data were analyzed using repeated measures ANOVA and Generalized Linear Modeling (GLM). Results The intervention group showed significantly lower respiratory rates and reduced incubator noise levels compared to the control group (p < 0.05), indicating meaningful improvements in physiological stability and the acoustic environment. A significant improvement in sleep patterns was observed at a specific measurement point; however, this effect was not consistent across all measurement periods. Conclusion Sound-absorbing incubator covers effectively reduce environmental noise and support respiratory stability in preterm infants, while their influence on sleep patterns warrants further investigation. © 2026 Neonatal Nurses Association.