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In phonetics, vowel roundedness refers to the amount of rounding in the lips during the articulation of a vowel. It is labialization of a vowel. When pronouncing a ''rounded'' vowel, the lips form a circular opening, whereas ''unrounded'' vowels (also called ''spread'' vowels) are pronounced with the lips relaxed. In most languages, front vowels tend to be unrounded, whereas back vowels tend to be rounded. But some languages, such as French and German, distinguish rounded and unrounded front vowels of the same height, whereas Vietnamese distinguishes rounded and unrounded back vowels of the same height. Alekano has only unrounded vowels. In the International Phonetic Alphabet vowel chart, rounded vowels are the ones that appear on the right in each pair of vowels. There are also diacritics, and , to indicate greater and lesser degrees of rounding, respectively. These 'more' and 'less rounded' diacritics are sometimes also used with consonants to indicate degrees of labialization. ==Types of rounding== There are two types of vowel rounding: ''protrusion'' and ''compression''.〔''Endolabial:'' also called ''protruded'', lip-pouting, horizontal lip-rounding, outrounding, and ''inner rounding'' (Trask 1996:180) ''Exolabial:'' also called ''compressed'', pursed, vertical lip-rounding, inrounding, or ''outer rounding'' (Trask 1996:252) Henry Sweet noted in 1890 that "the term 'inner rounding' derives from the use of the inner surfaces of the lips; the synonymous 'outrounding' derives from the forward projection of the lips. Both terms are justifiable, but their coexistence is likely to lead to serious confusion." (Trask 1996:180.)〕 In protruded rounding, the corners of the mouth are drawn together and the lips protrude like a tube, with their inner surface visible. In compressed rounding, the corners of the mouth are drawn together, but the lips are also drawn together horizontally ("compressed") and do not protrude, with only their outer surface visible. That is, in protruded vowels the inner surfaces of the lips form the opening (thus the alternate term ''endolabial''), whereas in compressed vowels it is the margins of the lips which form the opening (thus ''exolabial).'' Catford (1982:172) observes that back and central rounded vowels, such as German and , are typically protruded, whereas front rounded vowels such as German and are typically compressed. Back or central compressed vowels and front protruded vowels are uncommon,〔Henry Sweet ''(A handbook of phonetics,'' 1877) noted that they are less distinctive from unrounded vowels than their counterparts.〕 and a contrast between the two types has been found to be phonemic in only one instance.〔Japanese has a back compressed rather than protruded (Okada 1999:118); Swedish also has a back compressed as well as both front compressed and front protruded (Engstrand 1999:141); the front rounded vowels contrast in ''ryta'' 'roar' and ''ruta'' 'window pane' (Ladefoged & Maddieson 1996:295).〕 There are no dedicated IPA diacritics to represent the distinction, though the superscript IPA letter can be used for compression〔e.g. in Flemming (2002) ''Auditory representations in phonology'', p. 83.〕 and , or for protrusion. Compressed vowels may be pronounced either with the corners of the mouth drawn in, and so by some definitions rounded, or with the corners spread and by those same definitions unrounded. The distinction may be transcribed vs. . The distinction between protruded and compressed holds for the semivowels and as well as labialization. In Akan, for example, the is compressed, as are labio-palatalized consonants as in ''Twi'' "Twi" and ''adwuma'' "work", whereas and simply labialized consonants are protruded.〔''The Akan (Twi-Fante) Language: Its Sound Systems and Tonal Structure.'' Florence Abena Dolphyne, Ghana Universities Press, Accra, 1988. ISBN 9964-3-0159-6〕 In Japanese, the is compressed rather than protruded, paralleling the Japanese . The distinction applies marginally to other consonants. In Southern Teke, the sole language reported to have a phonemic , the labiodental sound is "accompanied by strong protrusion of both lips",〔Christiane Paulian (1975) ''Le kukuya, langue teke du Congo: phonologie, classes nominales''〕 whereas the found as an allophone of before in languages such as English is not protruded, as the lip contacts the teeth along its upper or outer edge. And in at least one account of speech acquisition, a child's pronunciation of ''clown'' involves a lateral with the upper teeth contacting the upper-outer edge of the lip, but in ''crown'' a non-lateral is pronounced with the teeth contacting the inner surface of the protruded lower lip.〔Kelly & Local (1989) ''Doing phonology'', p 41〕 Some vowels transcribed with rounded IPA letters may not be rounded at all. An example is , which in English has very little if any rounding of the lips. The "throaty" sound of English is instead accomplished with sulcalization, a furrowing of the back of the tongue also found in non-rhotic (Lass 1984:124). It is possible to mimic the acoustic effect of rounded vowels by narrowing the cheeks, so-called "cheek rounding", which is inherent in back protruded (but not front compressed) vowels. This technique is used by ventriloquists to mask the visible rounding of back vowels like .〔Henry Sweet, 1877, ''A handbook of phonetics'', vol. 2, pp 14, 20〕 It is not clear if it is employed by languages with rounded vowels that do not utilize visible rounding. : 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「roundedness」の詳細全文を読む スポンサード リンク
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