PURPOSE: To acoustically characterize the target productions of vibrant coda; to identify the presence (or not) of covert contrasts in productions omitting the vibrant coda; and to characterize how these contrasts are acoustically marked in speech. METHODS: Recordings of words produced by 30 children (3-4 years old) with typical language development were selected from a database using the software PRAAT. The words analyzed involved the production of the medial vibrant coda in stressed position, in the context of vowels /i/, /a/, and /u/. After auditory-perceptual characterization of the productions, an acoustic analysis was conducted considering the formant trajectory (F1, F2 and F3) and the relative length of the syllable containing the vibrant coda. Data were statistically analyzed. RESULTS: In the auditory-perceptual analysis, 77.8% of the productions were identified as the target vibrant coda, 12.2% were omitted, and 10% were substituted, varying according to the vowel context. In the acoustic analysis of target productions, it was verified that children preferably used acoustic parameters related to the formant trajectory of F2 and F3 to mark the acquisition of this structure. Analogously, in the acoustic analysis of omitted productions, it was identified the presence of covert contrasts, marked by the interception of the adopted acoustic parameters. CONCLUSION: Acoustic analysis seems to be a necessary and indispensable resource for describing and characterizing how children start mastering acoustic-phonetic cues, until they reach the effective contrast of the vibrant coda.