F1-F2 Plane Research Articles

Imitation of synthesized English and nonEnglish vowels by children and adults

Imitations of 15 synthesized vowels, some like English vowels and some not, were obtained from nine adults and ten 6-year-old children. Estimates of the first three formant frequencies (F 1 , F 2 , and F 3 ) were made from spectrograms of the vowel imitations. The reliability of reproduction was assessed by calculating standard deviations for five imitations each of ten of the synthetic stimuli. Generally, both the intrasubject and intersubject variabilities were greater for the children than for the adults. However, the differences in intrasubject variability between the two groups often were not much greater than the difference in measurement error which would be expected for voices of different fundamental frequencies. Subjects tended to reproduce the nonEnglish vowels less reliably than the English vowels, although the adults were less influenced by phonetic familiarity than were the children. Vowel familiarity appeared to be especially important for reliable reporoduction of the F 2 frequency. Plotting of the imitation data for English vowels in a F 1 –F 2 plane with linear dimensions revealed a fairly systematic clustering for the four age-sex groups of men, women, boys, and girls, but the group clustering was not so systematic for the imitation data for the nonEnglish vowels.

Some Measurements on the Vowel Sounds of Conversational Speech

Fairly well-defined and generally accepted regions of the (first formant frequency)—(second formant frequency) plane (referred to as the F1F2 plane) can be associated with each speech vowel sound. Delineation of the boundaries of these regions may be based on analysis of spoken vowels or on perception of synthesized vowels; in either case, the data are derived from the study of isolated vowels or monosyllables, and the resulting two sets of regions prove to be roughly the same. An alternative study, described in the paper, can be made, however, based instead on the vowel sounds occurring in “connected” or “conversational” speech. In this case the density of distribution of points within the F1F2 plane shows that there is little or no clustering of stationary points within the original (“monosyllable”) vowel regions and certainly permits neither identification of old, nor definition of new, regions. A set of tracks can be constructed, however, to correspond to the almost continuously moving F1F2 points and from these can be derived, by suitable processing, a new set of regions of simple shape, one region for each vowel sound as before. The differences between the set of regions for “monosyllable” vowels, i.e., the generally accepted set, and the set for “conversational” vowels, which may be reasonably regarded as the set in normal use, are striking. Two differences are (a) the set of vowel regions is now clustered very much more closely together than before and (b) for a given speaker the positions of “monosyllable” vowels do not even lie within the regions of the corresponding “conversational” vowels.