This paper documents the acoustic characteristics of what have been called devoiced vowels in Tokyo Japanese, traditionally attributed to the phonological rule of high vowel devoicing [T. J. Vance, Introduction to Japanese Phonology (1987)]. More recently they have been attributed to articulatory gesture overlap [S‐A. Jun and M. E. Beckman, Paper, Annual Meeting of the LSA (1993)]. Current research by the author indicates both processes are consistent with the data. The vowels which have undergone phonological processing, however, are not simply devoiced; they have undergone a process of obstruentization similar to that found in the Turkish language of Uyghur discussed both pedologically [R. F. Hahn, Spoken Uyghur (1991)] and phonologically [E. M. Kaisse, Language68, 313–332 (1992)]. Specifically, the vowel sites surface as voiceless fricatives at the place of articulation of the preceding voiceless consonant. This is evidenced acoustically by high‐frequency frication in spectrograms and a high number of zero crossings. Additionally, formant frequency information is preserved, as evidenced by formant bars in spectrograms and spectral sections, allowing the perception of the original vowels in the face of heavy loss of vocality.