Here is the design of a clinical trial:

Official Title: Effects of Early Vocal Contact (EVC) in the Neonatal Intensive Care Unit: A Multi-centre, Randomized Clinical Trial

Included conditions:
- Early Intervention
- Prematurity

Study Armgroups:
- {'label': 'Early Vocal Contact', 'type': 'EXPERIMENTAL', 'description': "The EVC will take place in the hospital room while infants are in their individual incubators or open cribs. In the intervention group, mothers will be asked to speak and sing to their infants continuously over a 10-min period for each type of intervention (20 min in total). Mothers will be asked to talk in their native language and to sing familiar songs, while observing their infant's reactions. The order of the two vocalizations, speaking and singing, will be reversed in the next intervention.\n\nEarly Vocal Contact will be performed by mothers three times a week for 2 weeks, more than one hour after afternoon feeding. It will begin when the newborns are in an active sleep state, in calm awake state or in active awake state, but not in deep sleep or crying. Preterm infants will be enrolled from 25+0 to 32+6 weeks of GA, following the established inclusion criteria.", 'interventionNames': ['Behavioral: Early Vocal Contact']}
- {'label': 'Behavioral observation', 'type': 'ACTIVE_COMPARATOR', 'description': "Mothers in the active control group will be encouraged to spend the same amount of time next to the incubator, observing the infant's behaviours through a standard cluster of indicators.", 'interventionNames': ['Behavioral: Behavioral Observation']}

Interventions:
- {'type': 'BEHAVIORAL', 'name': 'Early Vocal Contact', 'description': "Mothers will be asked to speak and sing to their infants continuously over a 10-min period for each type of intervention (20 min in total). Mothers will be asked to talk in their native language and to sing familiar songs, while observing their infant's reactions. The order of the two vocalizations, speaking and singing, will be reversed in the next intervention.", 'armGroupLabels': ['Early Vocal Contact']}
- {'type': 'BEHAVIORAL', 'name': 'Behavioral Observation', 'description': "Mothers in the active control group will be encouraged to spend the same amount of time next to the incubator, observing the infant's behaviours through a standard cluster of indicators.", 'armGroupLabels': ['Behavioral observation']}

Primary Outcomes:
- {'measure': 'Change in Heart Rate Variability', 'description': 'Heart rate is the number of heartbeats per minute.', 'timeFrame': 'Pre intervention (baseline), during the intervention and immediately after the intervention'}

Please estimate the sample size based on the assumption: 
Alpha setting at 0.025, beta setting at 0.80, and a 20% loss rate.
3.7. Sample Size and Power Analysis
        The main outcome measures for the primary outcome will be the low-frequency (LF) and high-frequency (HF) power of the HRV measure. We expect the baseline measurement mean value (Â±standard deviation) of LF and HF power for preterm infants to be 31 Â± 4.9 Hz and 15 Â± 2.6 Hz, respectively [58]. We assume that the treatment in the experimental population is effective if the mean values of LF and HF power reach 25 Â± 4.9 and 17 Â± 2.4 Hz, respectively. 
        With an alpha setting at 0.025 and beta setting at 0.80, it is necessary to enroll 29 patients per group. Assuming a 20% loss, we aim to enroll at least 80 patients total (40 per group).