This study aimed to determine the effect of maternal voice on physiological indicators and oral feeding performance in preterm infants.

Hypothesis 1 (H1): Preterm infants who listen to their mother's voice throughout the full oral feeding process have higher oxygen saturation levels than those who do not.

Hypothesis 2 (H2): Preterm infants who listen to their mother's voice throughout the full oral feeding process have lower heart rates than those who do not.

Hypothesis 3 (H3): Preterm infants exposed to maternal voice throughout the full oral feeding process have lower respiratory rates than those who are not exposed.

Hypothesis 4 (H4): Preterm infants exposed to maternal voice throughout the full oral feeding process have better feeding maturation than those who are not exposed.

Hypothesis 5 (H5): The percentage of nutrient intake in preterm infants exposed to maternal voice throughout the entire oral feeding process is higher than in those not exposed.

Hypothesis 6 (H6): The feeding time of preterm infants exposed to the mother's voice throughout the entire oral feeding process is shorter than that of those not exposed.

Hypothesis 7 (H7): The amount of food consumed per minute by preterm infants exposed to the mother's voice throughout the entire oral feeding process is greater than that of those not exposed.

Oral feeding is one of the critical milestones in the growth and development of preterm infants. A delay in achieving successful oral feeding skills may lead to prolonged hospitalization, negatively impact mother-infant bonding, result in long-term feeding difficulties, impair growth and development, and cause adverse neurodevelopmental outcomes. The literature reports that various methods have been used to enhance oral feeding performance, one of which is maternal voice. It has been reported that the maternal voice has a positive effect on the oral feeding performance of preterm infants. Continuing maternal vocal stimulation during the postnatal period (such as singing lullabies, reading books, or engaging in everyday speech) contributes to strengthening synaptic connections in the auditory cortex, increasing the brain's sensory processing capacity, reducing the infant's stress levels, and maintaining physiological stability. The maternal voice positively influences oral feeding performance by helping infants maintain an alert state and facilitating the coordination of sucking, swallowing, and breathing. In this regard, the maternal voice can be used as an evidence-based nursing intervention to enrich the care of preterm infants. However, the number of high-level evidence studies investigating the relationship between maternal voice and oral feeding performance is limited in the literature, and some existing studies report inconclusive results. Therefore, addressing this issue will help fill a gap in the literature.

In this study, preterm infants in the experimental group will listen to a lullaby recorded in their own mother's voice before and during oral feeding, twice daily (morning and evening) for five consecutive days. A Bluetooth-enabled, speaker-equipped voice recorder will be used for each infant individually. No auditory intervention will be applied to the infants in the control group. In both groups, physiological indicators and oral feeding performance will be measured on specific days.

Inclusion Criteria:

• Preterm infants born at gestational age ≥28 weeks and ≤34 weeks
• Infants who are ≥30 postmenstrual weeks old at the time of enrollment
• Infants weighing ≥1000 grams at the time of enrollment
• Mothers aged 18 years or older
• Preterm infants who have passed the hearing screening test
• Infants whose mothers can provide an average of at least 30 ml of expressed breast milk daily during the study period.
• Mothers who are Turkish speakers.
• Infants for whom the decision to transition from enteral feeding to full oral feeding has been made for the first time jointly by the physician and nurse

Exclusion Criteria:

• Preterm infants with congenital anomalies.
• Infants with a family history of congenital hearing loss.
• Infants diagnosed with intraventricular hemorrhage (grade 3-4) or -periventricular leukomalacia.
• Infants who have had necrotizing enterocolitis requiring treatment.
• Infants whose mothers have a history of substance abuse or alcoholism