Intrinsic Fundamental Frequency (IF0) and Tonal Gradient in Yorùbá
The present study investigates whether tones in tone languages constrain or control Intrinsic Fundamental Frequency (IF0), similar to the investigation conducted by Hombert (1977) and Connell (2002). Two native speakers of Yorùbá were recorded producing the seven vowels in the language with all three tones. Results of the analysis show that IF0 is found to be a gradient with respect to tones; the High tone possesses a higher F0 than the Mid tone, while the Low tone has the lowest. However, the results provide no strong evidence to support tonal gradient with respect to vowel heights. To some extent, the high vowel [u] appears to follow the prediction regarding tonal gradient, especially in comparison with the low vowel [a]; the other high vowel [i] does not. In most instances, the mid vowels record higher F0 than [i]. These mixed results are possibly due to some extralinguistic factors, such as the speakers’ habitual way of speaking, vocal tract shapes, and the larynx, among others.