The sibilants exist as allophones of and the fricative as an allophone of . The velar nasal is clearly an allophone of before a velar stop. The slender tap has a fricative allophone . They occur as the intervocalic allophone of glottal stop in many languages. Otherwise it is the intervocalic allophone of /d/. It is unusual for languages to lack phonemes whose primary allophone is a nasal. It also has a voiced allophone , which occurs before voiced obstruents. In Italian represents (where is the semivowel allophone of ). It does not occur initially and has a nasalized flap as a common allophone. The corresponding sound can be regarded as an allophone of the vowel in both languages. Some scholars treat as an unstressed allophone of . The diphthongs and may be interchanged since is an allophone of in final syllables. The sound , which had been a post-vocalic allophone of , became vocalized to . Likewise, some scholars treat as an allophone of the unstressed sequence . In Drubea, is reported as an allophone of before nasal vowels.