This paper deals with the acoustic characteristics of vocalic hesitations in a cross-language perspective. The underlying question concerns the ``neutral'' vs. language-dependent timbre of vocalic hesitations and the link between their vocalic quality and the phonetic system of the language. An additional point of interest concerns the duration effect on vocalic hesitation compared to intra-lexical vowels. Acoustic measurements have been carried out in American English, French and Spanish. Results on vocalic timbre show that hesitations (i) carry language-specific information; (ii) whereas often close to measurements of existing vowels, they do not necessarily collapse with them. Finally, (iii) duration variation affects the timbre of vocalic hesitation and a centralization towards a ``neutral'' realization is observed.