Problems with Description of Tense/Lax Vowels

English vowels are often described with the terms tense and lax. In the binary feature system, tense vowels are [+tense] and lax vowels are [-tense]. However, many linguists consider the terms tense and lax controversial. The reason is that these vowels can be distinguished by additional factors.

Tense vowels are defined as vowels with more muscular constriction. In addition, tense vowels are diphthongized in many varieties of English. Diphthongs often have a longer duration than do monophthongs.

Phonologists have frequently divided English vowels into tense and lax, but the tongue height is not the same. The tense vowel is higher and more peripheral than the lax vowel. The tense vowel also has an expanded pharynx, a more advanced articulation, and more lip rounding. The feature ATR (Advanced Tongue Root) can be used to distinguish tense and lax vowels. Tense vowels are classified as +ATR and lax vowels are -ATR.

According to Peter Ladefoged, the terms tense and lax are just used to designate two groups of vowels that behave differently in English words. He prefers to distinguish them in terms of the syllable types in which they occur. Though all vowels can occur in closed syllables, only a restricted set can occur in open syllables.

The tense vowel of pool can occur syllable-finally but the vowel of pull cannot. Likewise, the vowel of eat can occur syllable-finally but the vowel of sit cannot. However, it is important to mention that in certain dialects of English, the lax vowel occurs in words such as city. This is the case in most dialects of northern England.

Tense vowels are usually produced with greater length than in lax vowels, but this is not always the case. Length is not the criterion for distinguishing these vowel sets. The tense and lax vowels can be distinguished on the basis of height and tongue root configuration. Tense vowels have a more advanced tongue root than lax ones.

The terms tense and lax fail to capture all the differences between the two vowel sets. In addition to greater muscular constriction, tense vowels have a higher tongue position, more advanced tongue root, greater lip rounding and expanded pharynx. They usually have a longer duration than lax vowels and are diphthongized in many dialects. It is clear that the differences between tense and lax vowels involve more than muscular constriction.