Sleep is the cornerstone of early development. Adequate sleep in children is important for proper growth, development and the child's health. Sleep is a dynamic process that develops and matures rapidly, especially in the first few years of life, from infancy to early adolescence. Daily sleep duration decreases with age, starting from the newborn period. At birth, babies show a sleep process that is compatible with their mothers' circadian rhythm. Newborns usually wake up in line with their nutritional needs and have short transitional sleep periods. At approximately 10-12 weeks of age, the first signs of circadian rhythm begin to develop and become apparent with increased sleep during the night. It has been reported that music positively affects mother-infant bonding, reduces babies' stress and creates positive physiological and behavioral changes. In a study examining mothers' views and practices on singing lullabies, it was seen that 87.6% of mothers said that singing lullabies soothes their children and prepares them for sleep, 88.3% prefer to sing lullabies before going to sleep while preparing their children for sleep, and 66.2% sing lullabies. Therefore, it is thought that the research will fill this gap in newborns.

Sleep is the cornerstone of early development. At approximately 10-12 weeks of age, the first signs of the circadian rhythm begin to develop and become evident with increased nighttime sleep. The change in the total 24-hour sleep duration decreases as the baby grows, gradually adapting to the circadian sleep rhythm. Daily sleep duration in newborns decreases to 16-17 hours, 14-15 hours at 16 weeks of age, and 13-14 hours at 6 months of age. As the baby grows, the need for daytime sleep decreases, resulting in a shift towards more nighttime sleep patterns. In recent years, studies examining the effects of music, especially on newborns, have increased. Music is a complex auditory stimulus consisting of various components such as melody, rhythm, timbre, and harmony. When adults listen to music, these components are perceived as a phenomenological whole, but they are processed separately through a complex dual cortical and subcortical regions. Since the adult human brain does not have a single musical center, the neural substrates supporting musical perception and production vary depending on the musical task. Neuroimaging studies in neonates or infants have reported inconsistent results regarding cortical activation in response to musical stimuli. While two studies showed weak bilateral responses to musical stimuli, results from a functional magnetic resonance imaging (fMRI) study used to measure brain activity in 1- to 3-day-old neonates hearing excerpts of Western tone music and modified versions of the same excerpts suggest that the infant brain shows hemispheric specialization in right-lateralized auditory cortex activity for processing music in the early postnatal hours, and that the neural architecture underlying music processing in neonates is sensitive to changes in tone key as well as differences in consonance and dissonance. It has been found that infants can maintain distinct memory traces for polyphonic music and show a high preference for polyphonic music from 3 months onwards. Marie and Trainor (2014) hypothesize that this high-volume advantage may be mediated at the level of the auditory nerve at birth. In general, the presence of immature mismatch negativity (MMN) occurs when there is an occasional change or deviant stimulus in a continuing standard stimulus sequence. Again, this more complex MMN-like response to polyphonic stimuli has been reported to have a longer developmental trajectory than the MMN elicited by a single tone stimulus. Early musical involvement is very important for the auditory system, which mostly matures in the first 6 months after birth. Polyphonic lullabies, known in the literature as polyphony consisting of sounds or music, are music played especially during the rapid development period (0-4 years) of infants and children. When the literature was examined, no randomized controlled studies were found that revealed the effects of polyphonic lullabies and piş piş sounds on the transition to sleep and sleep duration in healthy newborns. It was thought that the research results would provide strong evidence to support the development of approaches to improving sleep in newborns.

Inclusion Criteria:

For newborns)

• Being healthy
• Being between 37th and 42nd weeks of gestation
• Being between 2500-4000 kg at birth
• Being exclusively breastfed for the first 3 months
• Not having a hearing problem detected by the newborn hearing test Criteria for inclusion in the study (For mothers)
• Not working for the first three months after birth
• Not having any known chronic physical or mental problems
• Not having any known sleep problems
• Being literate
• Being able to communicate in Turkish

Exclusion Criteria:

Exclusion criteria from the study (For newborns)

• Having a congenital anomaly
• Having a history of being in the neonatal intensive care unit
• Having any health problems
• Those who switched to mixed or formula feeding during the follow-up period

Exclusion criteria from the study (For newborns)

• Those who develop any disease in the newborn (convulsion, upper respiratory tract infection, urinary tract infection, etc.)
• Newborns in the experimental group who were not exposed to polyphonic lullaby/piş piş sounds for two consecutive days within 3 months and for a total of 5 days (Source.. I could not find a source here, lullaby studies conducted on preterm babies, if you want, I can add from those sources)
• Newborns who did not fill out a regular weekly sleep diary
• Newborns who were put to sleep by other sleep initiation methods such as breastfeeding or shaking to sleep other than the specified methods (polyphonic lullaby/piş piş sounds) will be excluded from the study.