A striking difference between vernacular and formal speech is the massive and systematic phonetic or low-level phonological reduction that occurs, deleting or modifying as much as 25-30% of the sounds expected on the basis of words' underlying forms (Veatch 1988). This commonly occurs with neither speaker nor hearer noticing it or often even being able to notice the deletions and reductions on having them pointed out. It is striking how different are the sounds we think we produce and hear from the sounds actually produced, which only careful listening for the phonetic reality will reveal. Prominent examples of reduction in dialects of English include flapping of /t/ and /d/, stops becoming fricatives, liquids becoming vocalic and other consonant manner lenitions; /r/-devoicing in voiceless clusters (as in ``tree'', where /r/ may sound more like  than a resonant retroflex ); voicing assimilation of (word-final) obstruents (as in the plural /z/ in ``the numbers seem'' -- cf. Veatch 1990); changes that take place when obstruents are juxtaposed through the deletion of intervening vowels; and vowel reduction, in quality and in amplitude, duration, pitch (range), and voicing. Perhaps the most technically tractable of this class of phonetic reduction phenomena, which may also display both dialect-specific and general effects, are the phenomena of vowel reduction, a central aspect of the present work.