Nasalization
From Freepedia
In phonetics, nasalization is the production of a sound while the velum is lowered, so that air escapes partially or wholly through the nose during the production of the sound.
In the International Phonetic Alphabet nasalization is indicated by printing a tilde above the symbol for the sound to be nasalized: [ã] is the nasalized equivalent of [a], and [ṽ] is the nasalized equivalent of [v].
Nasalized sounds are most often nasal vowels, as in French and Polish, or a Texas "twang".
However, there are also phonemically nasalized consonants. Some of the South Arabic languages have nasalized fricatives, such as [z̃]. The sound written r in Mandarin has an odd history; for example, it has been borrowed into Japanese as both [z] and [n]. It seems likely that this was a nasalized fricative at one time, perhaps a palatal [ʝ̃]. In the Hupa velar nasal /ŋ/, the tongue often does not make full contact, resulting in a nasalized approximant, [ɰ̃]. This is cognate with a nasalized [j̃] in other Athabaskan languages. In Umbundu, phonemic [ṽ] contrasts with allophonically nasalized [w̃], and so is likely to be a true fricative rather than an approximant.
