Vowel Quality

Two features of vowel quality that are used to contrast one vowel with another are height and backness. The vowel of he is high front, and the vowel of to is high back. In the word cat, the vowel is low front. However, other features can also be used to contrast vowel quality.

Four other features are rhotacization, rounding, ATR and nasalization. Height, backness and rhotacization reflect auditory properties, and the other three reflect articulatory properties with acoustic properties that differ from vowel to vowel.

Lip rounding tends to lower the second formant, but in the case of high front vowels it is primarily the third formant that is lowered. ATR and nasalization affect different formants in different vowels. The vowel of red is a mid front unrounded lax vowel. However, instead of the term lax, the term -ATR can also be used. The quality of height precedes the qualities of backness, rounding and ATR. The term ATR means advanced tongue root. The vowel of seat is +ATR, and the vowel of sit is -ATR.

Rhotacization is found in rhotic vowels of English. The word bird has a rhotic vowel in most varieties of American English, but a non-rhotic vowel in most varieties of British English. English has vowels that are ATR and -ATR, but many languages, i.e. Spanish, do not. English has nasalized vowels such as the vowel of sand, but the vowel is not fully nasalized because the nasal is also articulated. However, in languages such as French, vowels are often fully nasalized. The French word vin (wine) has a fully nasalized vowel. The nasal segment is thus not articulated.

Vowel quality is an important feature of vowels. The two features that are most associated with vowel quality are height and backness. In the articulatory description of vowels, height is given before backness and rounding.