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IPA – number	127
IPA – text	β
IPA – image
Entity	β
X-SAMPA	B
Kirshenbaum	B
Sound sample (help·info)

The voiced bilabial fricative is a type of consonantal sound, used in some spoken languages. The symbol in the International Phonetic Alphabet that represents this sound is ‹β›, and the equivalent X-SAMPA symbol is ‹B›. The symbol ‹β› is the Greek letter beta. This symbol is also sometimes used to represent the bilabial approximant, though that is more clearly written with the lowering diacritic, ‹β̞›. The bilabial fricative is diachronically unstable and is likely to shift to [v].^[1] In the English language, this sound is not used, but is made by making the normal "v" sound without fully closing the lips or without touching the top teeth to the lower lip.

Features

Features of the voiced bilabial fricative:

• Its manner of articulation is fricative, which means it is produced by constricting air flow through a narrow channel at the place of articulation, causing turbulence.
• Its place of articulation is bilabial which means it is articulated with both lips.
• Its phonation type is voiced, which means the vocal cords are vibrating during the articulation.
• It is an oral consonant, which means air is allowed to escape through the mouth.
• It is a central consonant, which means it is produced by allowing the airstream to flow over the middle of the tongue, rather than the sides.
• The airstream mechanism is pulmonic egressive, which means it is articulated by pushing air out of the lungs and through the vocal tract, rather than from the glottis or the mouth.

Occurrence

In the following transcriptions, the undertack diacritic may be used to indicate an approximant [β̞].

References

Bibliography

• Cruz-Ferreira, Madalena (1995), "European Portuguese", Journal of the International Phonetic Association 25 (2): 90–94  
• Gussenhoven, Carlos; Aarts, Flor (1999), "The dialect of Maastricht", Journal of the International Phonetic Association 29: 155–166  
• Ladefoged, Peter (2005). Vowels and Consonants (Second ed.). Blackwell.  
• Martínez-Celdrán, Eugenio; Fernández-Planas, Ana Ma.; Carrera-Sabaté, Josefina (2003), "Castilian Spanish", Journal of the International Phonetic Association 33 (2): 255–259  
• Picard, Marc (1987), "On the Palatalization and Fricativization of w", International Journal of American Linguistics 53 (3): 362-365  
• Pope, Mildred (1966). From Latin to Modern French. Manchester: Manchester University Press.  
• Merrill, Elizabeth (2008), "Tilquipan Zapotec", Journal of the International Phonetic Association 38 (1): 107–114  
• Wheeler, Max W (2005). The Phonology Of Catalan. Oxford: Oxford University Press. ISBN 0199258147.  

See also

• List of phonetics topics