Perceptual dimension of openness in vowels

The role of intrinsic factors determining perceived degree of vowel openness was examined. In order to determine the role of F1 and F0, one-formant vowels, covering a wide range of fundamental and formant frequencies, were identified by 23 subjects who were native speakers of a Bavarian dialect in which five degrees of openness occur distinctively. The significance of intrinsic factors other than F1 and F0 was also studied using synthetic versions of natural vowels with F1 and/or F0 systematically displaced in frequency. It was found that, generally, the tonality distance between F1 and F0 is decisive for openness, while the higher formants contribute marginally. It was further found that the distance between widely spaced formants, as between F2 and F1 in front vowels, is not crucial for vowel identification. The results are evaluated in terms of a psychoacoustic model of identification by pattern matching. the model incorporates two basic assumptions. First, a certain pattern of excitation along the basilar membrane is recognized as a given feature regardless of position along the membrane. Second, there is an integration band with a width of 3 Bark effective in spectrum envelope recognition.