In acoustic phonetic research, phonetic data is needed to prove authenticity. The acoustic phonetic analysis method is valid for verifying previous phonetic hypotheses. Thereby, lay the foundations of science to reinforce the notion of phonetic or phonetic study. The formant frequencies F1, F2, F3 are considered as the basis for measuring vowels. According to consonants, the length of VOT, formant transitions, antiformants, and locus frequencies will be noted. In this article, we present the basis to measure Vietnamese initial consonants such as: voiced consonants, voiceless consonants, stop consonants, fricative consonants, nasal consonants. The voiced consonants will have a voice bar and voiceless consonants will have no voice bar. Fricative consonants always have higher frequencies than stop consonants. Based on the spectral image of a consonant, we can determine the articulation of consonants. The acoustic properties of the nasal consonant and lateral consonant are nearly identical to the acoustic properties of the vowels, because in the construction of these consonants, the vocal cords are more vibrating.