This paper presents a systematic description of the 11 vowel phonemes (seven oral and four nasal vowels) of Siwu, the language of the people of Akpafu and Lolobi through a spectrographic analysis. The paper determines on scientific basis, the underlying acoustic parameters that characterize the vowel system of Siwu. The result of the study defines the acoustic vowel space of the language and shows that, the vowels are adequately dispersed within the vowel space as predicted by the maximal dispersion theory. The result further reveals that there are no significant dialectal differences between the two towns, (Akpafu and Lolobi) that constitute the Siwu language community – on the acoustic level.