The Vowels of the Pacific Northwest

The type of representation pictured in Figure 1 is a very common type of diagram used by linguistic phoneticians who study speech production. It's called a vowel space polygon (or vowel quadrilateral).


The symbols plotted on a vowel space diagram represent the key acoustic properties of individual vowels. Looking at the overall shape of the polygon, therefore, gives us a visual way of comparing the "shapes" of the vowel systems of different dialects.


Two properties serve as the most reliable cues. In the early days of the phonetic sciences, before the advent of x-ray and computer technology, phoneticians developed a method for representing vowels by the supposed position of the tongue. Two dimensions were used: the highest point or peak of the tongue, and the front or back location of this peak. These dimensions remain conceptually useful. However, recent technological advancements have clarified that what these phoneticians were in fact representing are better understood to be resonating frequencies of the vocal tract, called formant frequencies. Formant frequencies represent the vibrational characteristics of air in different locations inside the vocal tract as the tract takes on complex shapes during vowel production. The first formant frequency, abbreviated F1, has traditionally been associated with the height of the tongue (which shapes the air as it causes narrowing in the vocal tract). The second frequency, abbreviated F2, is taken as a reflection of the combined impacts of lip rounding and the position along the front-to-back axis of the tongue, where the tongue body is highest (which creates bodies of air before and behind the raised tongue). F2 and F1 are plotted as the x and y coordinates, respectively, on a vowel space polygon. The axes are reversed to fit with the historical idea of the configuration of the tongue relative to the teeth for an /i/ as in BEET (the highest part of the tongue is in the front of the mouth) vs. an /u/ as in BOOT (where the highest part of the tongue is in the back of the oral cavity).


In this way, this type of representation can reflect the fact that the vocal tract takes on particular shapes for particular vowels. We may average standardized values of F1 and F2 over many individual speakers, or for different ages or genders, and plot these averages to obtain an overall depiction of the characteristics of the vowel systems of different groups.

Want to learn more?

Interested readers are encouraged to learn more about representations of vowel systems in Peter Ladefoged’s book, Vowels and Consonants.

References

Ladefoged, P. & Disner, S. F. (2012). Vowels and Consonants. Hoboken, NJ: John Wiley & Sons.

Wassink, A. B. (2015). “Sociolinguistic Patterns in Seattle English” Language Variation and Change 27(1): 31-58. [DOI]