The voiceless bilabial fricative is a type of consonantal sound, used in some spokenlanguages. The symbol in the International Phonetic Alphabet that represents this sound is ⟨ɸ⟩. For English-speakers, it is easiest to think of the sound as an f-sound made only with the lips, instead of the upper teeth and lower lip, or a blowing sound.
Its phonation is voiceless, which means it is produced without vibrations of the vocal cords. In some languages the vocal cords are actively separated, so it is always voiceless; in others the cords are lax, so that it may take on the voicing of adjacent sounds.
It is an oral consonant, which means air is allowed to escape through the mouth only.
Because the sound is not produced with airflow over the tongue, the central–lateral dichotomy does not apply.
Okada, Hideo (1999), "Japanese", in International Phonetic Association (ed.), Handbook of the International Phonetic Association: A Guide to the Use of the International Phonetic Alphabet, Cambridge University Press, pp. 117–119, ISBN978-0-52163751-0
Pérez, Ramón Morillo-Velarde; Aguilar, Rafael Cano; Jiménez, Antonio Narbona (1998), El Español hablado en Andalucía, ISBN84-344-8225-8