the nineteen non-approximant consonants of Standard Korean, and Jeju displays the three-way contrast between stops and affricates characteristic of Modern Korean. Whether the voiced glottal fricative , absent in Standard Korean, exists as a phoneme in Jeju or merely as an allophone of remains disputed. A 2000 acoustic and aerodynamic study of eight native Jeju speakers concludes that "the consonants of the two languages seem to be the same in every respect... the phonetic realization of all [Jeju] consonants are the same as those found in [Seoul] Korean." Consonantal phonological processes Jeju allophony involves a number of phonological processes also found in Seoul Korean. As in Korean, surfaces as intervocally. Also as in Korean, lax stops and affricates have fully voiced allophones in medial position, all obstruents have unreleased allophones in final position, and syllable-final sibilants surface as . Whether non-lax stops and affricates can appear in final position is controversial. The morphological analysis necessary for the government's orthography permits them, while the analysis behind the Jeju Language Research Society's orthography forbids them. Most non-morphophonological consonant assimilation rules of Standard Korean are also found in Jeju. and are regularly palatalized to before or . Lax obstruents are tensed following another obstruent. aspirates both the preceding and the subsequent lax obstruent. A nasal consonant nasalizes a preceding obstruent or . becomes following all consonants except itself or , and this can itself nasalize the preceding obstruent so that the underlying sequence is realized as . On the other hand, underlying and both produce . Jeju also has consonant allophones that appear only at morpheme boundaries. Some of these are found in Standard Korean, such as the insertion of before or at most word-internal morpheme boundaries; the palatalization of to before an affixal ; and the tensing of obstruents following certain morpheme-final nasals. Other rules are absent in Standard Korean. For instance, a sonorant-final word or morpheme can trigger aspiration (for older speakers) or tensing (for younger speakers) in a subsequent lax consonant. In some cases this is due to an underlying consonant cluster, but not all cases can be explained in this way. Other Jeju-specific processes include the doubling of a word-final consonant when followed by a vowel, glide, or , and the lenition of to at some word boundaries. Verbal conjugation can also lead to consonantal changes. Verb stem-final and are lost before . In the case of verb stems