Phonetics of vowels
Vowel inventories are a major point of distinction among accents of English: not simply in their phonetic implementation but also in their phonological arrangement. Some accents maintain contrasts between phonemes that others have lost, while other accents are splitting phonemes into to new, separate categories. Californian English is known to have the "low-back merger", whereby all words such as thought, taut, and hawk have the same vowel as words such as lot, tot, and hock. Like other accents of the West, it also typically has a centralized nucleus of the diphthongs in words such as goose and food.

Some other aspects of Californian vowel space that are in progress include the California shift and the centralization of the /ow/ vowel in words like goat and home. The figure below illustrates the distribution of vowels in phonetic space for a small sample of Californian English speakers, by plotting F2 as an analog of the front/back dimension and F1 as an analog of the low/high dimension. Speakers are placed in the same vowel space using log normalization based on Nearey 1978.

Log normalized averages of vowels categories for 13 CA speakers

In this graph, we can see first that the nucleus of the /uw/ vowel of goose is quite front. But in addition, the short front vowels are each lower than one would expect otherwise in an American English quadrangle: notably, the /ih/ vowel of kit is actually lower than the /ey/ vowel of face. Meanwhile, the /eh/ of dress and /ae/ of trap are similarly lower in the front vowel space. In other words, the relative height distinction between the three vowels is intact, but each has dropped in sequence. Meanwhile, the /ow/ (goat) and /a/ (lot) vowels are central in the front-back dimension: thus, though these speakers have no lot-thought contrast, the lot-thought merger is situated in the low-central vowel space rather than the low-back region.

Research on phonetics of vowels