Intelligibility of sung vowels: the effect of consonantal context and the onset of voicing.

BACKGROUND: Studies addressing the identification of sung vowels concern mainly the effect of the fundamental frequency (f0) and conclude that correct vowel identification decreases with increasing pitch. In one experiment, the impact of consonantal environment on the intelligibility of the vowels in high-pitched singing was also studied. The results of that experiment showed positive effect of the consonantal environment. This finding is in line with results that had been reported for speech in an earlier study. However, the data on singing are not as transparent as the authors suggest, and there are some conditions in the experiment that could also be controlled for more strictly. Therefore, the effect of the dynamic acoustic information encoded in the formant transitions at high fundamental frequencies is still an open question.

OBJECTIVES: The aim of the present study was to redesign and extend the above-mentioned experiment to test whether the phonetic context and the onset of the vowel uttered in isolation (namely the onset of voicing) have a positive effect on vowel identification.

METHODS: For this purpose, a vowel identification test was carried out. The stimuli included three Hungarian vowels /aː iː uː/ in three conditions (in /bVb/ context, in isolation and with eliminated onset) at seven different fundamental frequencies from 175 to 988 Hz (F3, B3, F4, B4, F5, B5, and speech). The stimuli were produced by one professional soprano singer.

RESULTS: The results show that consonantal context does not specify vowel identity in singing as clearly as it has been demonstrated for spoken utterances. In addition, no effect of vowel onset (ie, the onset of voicing) was found. Recognition percentages seemed only to be dependent on f0 and vowel quality.

CONCLUSIONS: The unexpected results lend themselves to two possible explanations: the reduction of the consonants and the undersampling of the formant transitions.