Explaining the Dispersion of the Single-Vowel Occurrences in an F1/F2 Space

Abstract

Abstract The variability of the Finnish vowel occurrences on the F₁/F₂ chart was studied. Repetitions (n = 8 x 10 + 10 = 160) of two syllable types, /hVh/ and /tVt/, produced by a male speaker were analysed. The F₁/F₂ variability in both contexts was estimated. In the /hVh/ context, the phoneme targets were considerably more peripheral than in the /tVt/ contexts. In the /tVt/ context, the phoneme placements were nearer the upper left corner of the F₁/F₂ space in /u/, /o/, /a/, and /æ/. That is understandable on the basis of the alveolar tongue blade position: the tongue holds its position nearer the alveolar area during its movement from [t] to [V] and back to [t] compared to the [hVh] articulation. In the latter articulation, the tongue is free to move and the vowel reaches its ideal position. This interpretation was corroborated by means of the test items with an open syllable (/tVV/). In order to explain the variability of the repetitions in one context, the notion of auditory critical band window (CBW) was used. A CBW covers an area on the psycho-acoustical F₁/F₂ plot that comprises 1 bark on the F₁ and F₂ scales. Its modification CBW-F₁ implies that a critical band is presented as a circle comprising the diameter of 1 bark according to the F₁ scale. Practically all single F₁/F₂ points occur within the CBW-F₁ circle. In most cases, the variability is smaller than one CBW-F₁ circle, but we can consider that a greater amount of repetions would yield a greater dispersion. The auditorily motivated CBW-F₁ circle might appear to be a good prediction for the articulation precision.