throughout many English dialects, though the phonetic realisation of e.g. rather than (a phenomenon called happy-tensing) is not as universal. Unstressed vowels vary in quality: (as in ) ranges from close front to close-mid retracted front ; (as in ) ranges from close advanced back to close-mid retracted central ; according to the phonetician Jane Setter, the typical pronunciation of this vowel is a weakly rounded, mid-centralized close back unrounded vowel, transcribed in the IPA as or simply ; (as in ) ranges from close-mid central to open-mid central . Diphthongs and triphthongs The centring diphthongs are gradually being eliminated in RP. The vowel (as in door, boar) had largely merged with by the Second World War, and the vowel (as in poor, tour) has more recently merged with as well among most speakers, although the sound is still found in conservative speakers, and in less common words such as boor. See – merger. More recently has become a pure long vowel , as explained above. is increasingly pronounced as a monophthong , although without merging with any existing vowels. The diphthong is pronounced by some RP speakers in a noticeably different way when it occurs before , if that consonant is syllable-final and not followed by a vowel (the context in which is pronounced as a "dark l"). The realization of in this case begins with a more back, rounded and sometimes more open vowel quality; it may be transcribed as or . It is likely that the backness of the diphthong onset is the result of allophonic variation caused by the raising of the back of the tongue for the . If the speaker has "l-vocalization" the is realized as a back rounded vowel, which again is likely to cause backing and rounding in a preceding vowel as coarticulation effects. This phenomenon has been discussed in several blogs by John C. Wells. In the recording included in this article the phrase "fold his cloak" contains examples of the diphthong in the two different contexts. The onset of the pre- diphthong in "fold" is slightly more back and rounded than that in "cloak". RP also possesses the triphthongs as in tire, as in tower, as in lower, as in layer and as in loyal. There are different possible realisations of these items: in slow, careful speech they may be pronounced as two syllables with three distinct vowel qualities in