The purpose of this study is to evaluate the effectiveness of the AI-based application "HiDongDong" in improving articulation development in children aged 2 to under 14 years with suspected articulation delays. The program provides individualized language training based on a personalized assessment of vulnerable speech sounds. This trial aims to determine whether the digital therapeutic solution can enhance articulation skills and inform future strategies for language rehabilitation in children.

This exploratory randomized controlled trial (RCT) evaluates the effectiveness of the AI-based application "HiDongDong" in improving articulation in children aged 2 to under 14 years with suspected articulation delays.

1. Study Methods

1. Screening and Enrollment Children suspected of articulation developmental delay will be assessed for eligibility according to predefined inclusion and exclusion criteria. Eligible participants will be enrolled, randomized, and scheduled for study visits.

2. Visit 1 - Baseline Assessment

   At the first visit, a blinded assessor will collect demographic data (child's age, sex, and underlying medical conditions) and conduct a single baseline assessment, including the following:

   • Language assessments: U-TAP (Urimal Test of Articulation and Phonology)

     • SELSI (Sequenced Language Scale for Infants) or PRES (Preschool Receptive- Expressive Language Scale)

   • Functional independence: WeeFIM (Functional Independence Measure for Children)

   • Caregiver emotional status: Satisfaction (5-point Likert scale), depression (BDI; Beck Depression Inventory), anxiety (BAI; Beck Anxiety Inventory)

   • Clinician satisfaction: 5-point Likert scale

3. Post-Assessment Procedures Following baseline assessment, the control group will be discharged and return home. For the intervention group, a personalized language training program will be generated based on the results of the HiDongDong assessment.

4. Training and Orientation Participants in the intervention group will receive instruction on how to use the HiDongDong language training program, along with guidance on the study procedures.

5. Intervention Period The intervention group will complete the HiDongDong language training program at home under caregiver supervision for 4 weeks, 5 sessions per week, 20 minutes per session. Adherence will be monitored throughout the intervention period. The control group will receive language training provided by a speech-language pathologist.

6. Visit 2 - Post-Intervention Assessment and Study Completion Four weeks after the intervention, both the control and intervention groups will undergo a single post-intervention assessment conducted by a blinded assessor. Upon completion of the assessment, follow-up will be concluded.

2. Comparator and Randomization Participants will be randomized by an independent statistician affiliated with the Medical Research Collaborating Center of the Biomedical Research Institute at Seoul National University Bundang Hospital (SNUBH), using SAS version 9.4.

Assessor blinding will be applied. A blinded assessor (e.g., a hospital-based speech-language pathologist) will conduct all assessments without knowledge of each participant's group allocation, in an independent time and setting.

The sole difference between the two groups is the provider of the intervention:

• Control group: Language training delivered by a speech-language pathologist
• Intervention group: Language training delivered via the HiDongDong application (investigational medical device)

Participants will return after 4 weeks for post-intervention assessment by a blinded assessor, after which follow-up will be concluded.

To prevent interim analysis, assessment results will not be disclosed to any study personnel until the dataset is complete.

Inclusion Criteria:

1. Children aged 2 years to under 14 years
2. Persistent difficulties in speech sound production, or reduced speech intelligibility that interferes with communicative participation, resulting in limitations in social participation, academic performance, or daily activities
3. Articulation developmental delay suspected based on U-TAP results, with articulation performance more than 1 standard deviation below the mean for the same age group (-1SD)
4. Sufficient cognitive ability to follow simple instructions via a mobile device (tablet)
5. For children under 7 years of age: a caregiver who has received sufficient explanation of the study purpose and procedures and has voluntarily provided written informed consent
6. For children aged 7 years or older: voluntary assent from the child after sufficient explanation of the study purpose and procedures by the investigator,

in addition to written informed consent from the caregiver

Exclusion Criteria:

1. Caregiver or child does not consent to study participation, or withdraws consent during the study
2. U-TAP results indicate articulation development within the normal range, with no suspicion of articulation developmental delay
3. Difficulty understanding simple instructions or participating in assessments and training due to moderate or severe cognitive impairment, attention deficit, autism spectrum disorder, or similar conditions
4. Significantly limited speech production due to neuromuscular or anatomical causes, including severe visual impairment or visual field deficits, hearing impairment, cleft palate structural abnormalities, or severe oral/facial muscle dysfunction, resulting in difficulty with articulation
5. Inability to continue study participation due to acute illness or other conditions that may affect assessment or training during the study period, or unwillingness of the caregiver or child to continue participation
6. Determination by the principal investigator that study participation may pose a risk to the safety or well-being of the child

Any one of the above exclusion criteria is sufficient for exclusion.

Individual participant data collected during the study will not be shared, in order to protect the privacy of pediatric participants and in accordance with institutional policy.

• Outcome Assessors (individuals evaluating pre- and post-intervention articulation performance)
• Participants and treating clinicians are aware of group assignment, but the evaluators conducting articulation assessments are blinded to the intervention group to reduce bias.